Added transcription of audio and video files to local data sources (#1081)

Co-authored-by: Paul Koudelka <106623909+PaulKoudelka@users.noreply.github.com>

app/MindWork AI Studio/Tools/Services/DataBackupService.cs

@@ -170,7 +170,7 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
             var settingsJson = JsonSerializer.Serialize(settings, SettingsManager.JSON_OPTIONS);
             var organizationPluginFolders = DataBackupContents.FindOrganizationPluginsAmongUserPlugins(PluginFactory.AvailablePlugins.OfType<IAvailablePlugin>(), dataDirectory);
 
-            indexCopiesDirectory = await this.CopyIndexesAsync(token);
+            indexCopiesDirectory = await this.CopyIndexesAsync(dataDirectory, token);
 
             var sources = new DataBackupSources(dataDirectory, configDirectory, settingsJson, indexCopiesDirectory, organizationPluginFolders);
             var manifest = new DataBackupManifest(
@@ -207,7 +207,7 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
     }
 
     /// <summary>
-    /// Copies both indexes of the data sources, while the indexing pauses.
+    /// Copies both indexes of the data sources and the transcripts of their media files, while the indexing pauses.
     /// </summary>
     /// <remarks>
     /// Both copies are made during one pause: the vector stores have to fit to the index, or a
@@ -217,8 +217,10 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
     ///
     /// Without either database, the backup leaves both indexes out, and its manifest says so.
     /// </remarks>
+    /// <param name="dataDirectory">The data folder, which holds the transcripts.</param>
+    /// <param name="token">The cancellation token.</param>
     /// <returns>The directory of the copies, in the layout of the data folder, or an empty string when the backup leaves the indexes out.</returns>
-    private async Task<string> CopyIndexesAsync(CancellationToken token)
+    private async Task<string> CopyIndexesAsync(string dataDirectory, CancellationToken token)
     {
         var indexStore = await databaseClientProvider.GetIndexStoreAsync(token);
         var vectorStore = await databaseClientProvider.GetVectorStoreAsync(token);
@@ -241,6 +243,12 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
                 await vectorStore.CopyStoreForBackupAsync(preparation.BackupId, preparation.Stores[index].StoreName, token);
             }
 
+            //
+            // The index knows which transcript belongs to which media file, so the transcripts are
+            // copied while the indexing pauses as well, and the backup holds both as they fit together:
+            //
+            await DataSourceTranscriptStore.CopyAllAsync(dataDirectory, preparation.StagingPath, token);
+
             return preparation.StagingPath;
         }
         catch

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingIgnoreReason.cs

@@ -5,6 +5,24 @@ namespace AIStudio.Tools.Services;
 /// </summary>
 public enum DataSourceEmbeddingIgnoreReason
 {
-    MEDIA_NOT_SUPPORTED,
+    /// <summary>
+    /// An image, which cannot be added to the index yet.
+    /// </summary>
+    IMAGE_NOT_SUPPORTED,
+
+    /// <summary>
+    /// An audio or video file without a transcript, while no usable transcription provider is configured.
+    /// </summary>
+    TRANSCRIPTION_PROVIDER_MISSING,
+
+    /// <summary>
+    /// An audio or video file without a transcript, while the transcription provider falls short of
+    /// the confidence level the data source asks for.
+    /// </summary>
+    TRANSCRIPTION_PROVIDER_NOT_ALLOWED,
+
+    /// <summary>
+    /// A file larger than the limit of the data source.
+    /// </summary>
     TOO_LARGE,
 }

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingIgnoredFile.cs

@@ -6,7 +6,8 @@ namespace AIStudio.Tools.Services;
 /// </summary>
 /// <remarks>
 /// Files below folders the user chose not to scan never reach enumeration and therefore do not
-/// appear here. Temporary and system files are implementation details and stay hidden as well.
+/// appear here. Generated transcript artifacts and temporary/system files are implementation
+/// details and stay hidden as well.
 /// </remarks>
 /// <param name="FilePath">The absolute path of the ignored file.</param>
 /// <param name="Reason">Why the file was ignored.</param>

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingService.cs

@@ -7,6 +7,7 @@ using AIStudio.Settings.DataModel;
 using AIStudio.Tools.Databases;
 using AIStudio.Tools.Databases.IndexStore;
 using AIStudio.Tools.Databases.VectorStore;
+using AIStudio.Tools.Media;
 using AIStudio.Tools.PluginSystem;
 using AIStudio.Tools.Security;
 using AIStudio.Tools.Services.Indexing;
@@ -16,7 +17,7 @@ using static AIStudio.Tools.Services.Indexing.IndexingLogFormat;
 namespace AIStudio.Tools.Services;
 
 public sealed partial class DataSourceEmbeddingService(SettingsManager settingsManager, RustService rustService, DatabaseClientProvider databaseClientProvider,
-    PromptInjectionGuardService guardService, ILogger<DataSourceEmbeddingService> logger) : BackgroundService, IMessageBusReceiver
+    PromptInjectionGuardService guardService, MediaTranscriptionService mediaTranscriptionService, ILogger<DataSourceEmbeddingService> logger) : BackgroundService, IMessageBusReceiver
 {
     /// <summary>
     /// How long the re-index check waits for the index database before it gives up.
@@ -40,7 +41,7 @@ public sealed partial class DataSourceEmbeddingService(SettingsManager settingsM
     /// <summary>
     /// One indexer per kind of data source this service indexes.
     /// </summary>
-    private readonly IReadOnlyList<IIndexedSourceIndexer> indexers = CreateIndexers(settingsManager, rustService, guardService, logger);
+    private readonly IReadOnlyList<IIndexedSourceIndexer> indexers = CreateIndexers(settingsManager, rustService, guardService, mediaTranscriptionService, logger);
 
     private readonly DataSourceRunQueue runQueue = new();
 
@@ -93,12 +94,12 @@ public sealed partial class DataSourceEmbeddingService(SettingsManager settingsM
     /// <summary>
     /// Creates one indexer per kind of data source, all of them cutting their text with the same chunker.
     /// </summary>
-    private static IReadOnlyList<IIndexedSourceIndexer> CreateIndexers(SettingsManager settingsManager, RustService rustService, PromptInjectionGuardService guardService, ILogger logger)
+    private static IReadOnlyList<IIndexedSourceIndexer> CreateIndexers(SettingsManager settingsManager, RustService rustService, PromptInjectionGuardService guardService, MediaTranscriptionService mediaTranscriptionService, ILogger logger)
     {
         var textChunker = new TextChunker(rustService, logger);
         return
         [
-            new FileSourceIndexer(settingsManager, rustService, textChunker, logger),
+            new FileSourceIndexer(settingsManager, rustService, mediaTranscriptionService, textChunker, logger),
             new MailboxIndexer(settingsManager, rustService, guardService, textChunker, logger),
         ];
     }
@@ -518,10 +519,35 @@ public sealed partial class DataSourceEmbeddingService(SettingsManager settingsM
 
         this.statuses.TryRemove(dataSource.Id, out _);
         await this.ResetPersistedStateAsync(dataSource.Id, null, null, CancellationToken.None);
+        this.DeleteMediaTranscripts(dataSource);
         this.statuses.TryRemove(dataSource.Id, out _);
         PublishStatusChanged();
     }
 
+    /// <summary>
+    /// Deletes the transcripts of the audio and video files of a data source which the user removed.
+    /// </summary>
+    /// <remarks>
+    /// Only the removal of a data source does this. A reset for new embedding settings keeps them,
+    /// cf. ResetPersistedStateAsync: they are still valid, and the new index would otherwise pay
+    /// for every recording once more.
+    /// </remarks>
+    /// <param name="dataSource">The removed data source.</param>
+    private void DeleteMediaTranscripts(IDataSourceBase dataSource)
+    {
+        if (dataSource is not (DataSourceLocalDirectory or DataSourceLocalFile))
+            return;
+
+        try
+        {
+            DataSourceTranscriptStore.TryForDataSource(dataSource.Id)?.DeleteAll();
+        }
+        catch (Exception exception)
+        {
+            logger.LogWarning(exception, "Could not remove the transcripts of the deleted data source '{DataSourceName}' ({DataSourceId}).", dataSource.Name, dataSource.Id);
+        }
+    }
+
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {
         // Changes to the embedding settings which do not pass through the queue, cf. ProcessMessage:
@@ -1086,6 +1112,18 @@ public sealed partial class DataSourceEmbeddingService(SettingsManager settingsM
         ? embeddingProviderConfidence.AllowsMailboxConfidenceLevel(dataSource.ConfidenceLevel)
         : embeddingProviderConfidence.AllowsDataSourceConfidenceLevel(dataSource.ConfidenceLevel);
 
+    /// <summary>
+    /// Whether a transcription provider of the given confidence level may hear the audio and video files of a data source.
+    /// </summary>
+    /// <remarks>
+    /// The transcription provider receives the content of the data source just like the embedding
+    /// provider does, so the same rule applies to both, cf. AllowsEmbedding.
+    /// </remarks>
+    /// <param name="dataSource">The data source to index.</param>
+    /// <param name="transcriptionProviderConfidence">The confidence level of the transcription provider.</param>
+    /// <returns>True when the provider may transcribe the media files of the data source.</returns>
+    internal static bool AllowsTranscription(IIndexedDataSource dataSource, ConfidenceLevel transcriptionProviderConfidence) => AllowsEmbedding(dataSource, transcriptionProviderConfidence);
+
     /// <summary>
     /// The configured data sources this service indexes, from every list which holds some.
     /// </summary>

app/MindWork AI Studio/Tools/Services/DataSourceEmbeddingStatus.cs

@@ -68,6 +68,13 @@ public sealed record DataSourceEmbeddingStatus(
     /// </summary>
     public int SkippedDocuments => this.PermanentlySkippedDocuments + this.IgnoredFiles.Count;
 
+    /// <summary>
+    /// Whether selected audio or video files wait for a transcription provider which this data
+    /// source allows, so they cannot be indexed until the settings change.
+    /// </summary>
+    public bool NeedsTranscriptionProvider => this.IgnoredFiles.Any(file =>
+        file.Reason is DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_MISSING or DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_NOT_ALLOWED);
+
     /// <summary>
     /// The settled health of this data source. Activity is represented by State
     /// instead, so queued and running sources can keep their activity indicator.
@@ -84,7 +91,8 @@ public sealed record DataSourceEmbeddingStatus(
             if (this.State is DataSourceEmbeddingState.FAILED || this.FailedDocuments > 0)
                 return DataSourceEmbeddingHealth.ERROR;
 
-            if (this.State is DataSourceEmbeddingState.COMPLETED && this.IndexedDocuments == 0 && this.SkippedDocuments > 0)
+            if (this.NeedsTranscriptionProvider ||
+                this.State is DataSourceEmbeddingState.COMPLETED && this.IndexedDocuments == 0 && this.SkippedDocuments > 0)
                 return DataSourceEmbeddingHealth.WARNING;
 
             return DataSourceEmbeddingHealth.HEALTHY;

app/MindWork AI Studio/Tools/Services/EmbeddedFileRecord.cs

@@ -1,3 +1,3 @@
 namespace AIStudio.Tools.Services;
 
-public sealed record EmbeddedFileRecord(string Fingerprint, long FileSize, DateTimeOffset LastWriteUtc, DateTimeOffset EmbeddedAtUtc, int ChunkCount);
+public sealed record EmbeddedFileRecord(string Fingerprint, long FileSize, DateTimeOffset LastWriteUtc, DateTimeOffset EmbeddedAtUtc, int ChunkCount, string? TranscriptKey = null);

app/MindWork AI Studio/Tools/Services/Indexing/DocumentRunProgress.cs

@@ -226,7 +226,7 @@ internal sealed class DocumentRunProgress(IndexedRunContext context, int totalDo
         var embeddedAtUtc = DateTimeOffset.UtcNow;
         var state = document.State with { ChunkCount = chunkCount, EmbeddedAtUtc = embeddedAtUtc };
         await context.IndexStore.UpsertFileAsync(context.DataSource.Id, state, token);
-        context.Manifest.Files[document.Key] = new EmbeddedFileRecord(state.Fingerprint, state.FileSize, state.LastWriteUtc, embeddedAtUtc, chunkCount);
+        context.Manifest.Files[document.Key] = new EmbeddedFileRecord(state.Fingerprint, state.FileSize, state.LastWriteUtc, embeddedAtUtc, chunkCount, state.TranscriptKey);
         await context.ForgetPermanentFailureAsync(document.Key, token);
         context.Pass.Forget(document.Key);
 
@@ -300,7 +300,7 @@ internal sealed class DocumentRunProgress(IndexedRunContext context, int totalDo
                 //
                 this.PermanentlySkippedDocuments++;
                 var occurredAtUtc = DateTimeOffset.UtcNow;
-                var indexingMessage = this.GetFailureMessage(extractionFailure.Code, document);
+                var indexingMessage = this.GetFailureMessage(extractionFailure.Code, document, extractionFailure.Message);
                 this.failures.Add(new DataSourceEmbeddingFailure(document.Key, indexingMessage, occurredAtUtc, ExtractionCode: extractionFailure.Code, IsPermanent: true, DisplayName: document.DisplayName));
                 context.Manifest.Files.Remove(document.Key);
                 context.Pass.Forget(document.Key);
@@ -533,10 +533,37 @@ internal sealed class DocumentRunProgress(IndexedRunContext context, int totalDo
     /// </remarks>
     /// <param name="code">Why reading the document failed, NONE when it was not about reading it.</param>
     /// <param name="document">The document.</param>
+    /// <param name="details">A localized explanation supplied by a specialized reader, when available.</param>
     /// <returns>The message, ready to show.</returns>
-    private string GetFailureMessage(FileExtractionErrorCode code, EmbeddingDocument document) => context.DataSource is DataSourceMailbox
-        ? string.Format(TB("The mail '{0}' could not be indexed. AI Studio tries again during the next sync."), document.DisplayName)
-        : code.ToIndexingUserMessage(document.DisplayName);
+    private string GetFailureMessage(FileExtractionErrorCode code, EmbeddingDocument document, string? details = null)
+    {
+        if (context.DataSource is DataSourceMailbox)
+            return string.Format(TB("The mail '{0}' could not be indexed. AI Studio tries again during the next sync."), document.DisplayName);
+
+        if (code is FileExtractionErrorCode.MEDIA_PROCESSING_FAILED && !string.IsNullOrWhiteSpace(details))
+        {
+            return string.Format(
+                TB("The media file '{0}' could not be processed, so it was not indexed. Reason: {1} AI Studio reads it again as soon as the file changes."),
+                document.DisplayName,
+                AsSentence(details));
+        }
+
+        return code.ToIndexingUserMessage(document.DisplayName);
+    }
+
+    /// <summary>
+    /// Ends a reason with a full stop, so the sentence after it does not run into it.
+    /// </summary>
+    /// <remarks>
+    /// Providers write their error messages as they like, often without a full stop at the end.
+    /// </remarks>
+    /// <param name="reason">The reason.</param>
+    /// <returns>The reason, ending with a punctuation mark.</returns>
+    internal static string AsSentence(string reason)
+    {
+        var sentence = reason.TrimEnd();
+        return sentence.Length is 0 || sentence[^1] is '.' or '!' or '?' or '…' ? sentence : $"{sentence}.";
+    }
 
     private DataSourceEmbeddingStatus CreateStatus(DataSourceEmbeddingState state, string currentDocument, string lastError, int? currentBlock, int? currentPage, DataSourceAttention attention = DataSourceAttention.NONE, int? pendingRemovalCount = null) => new(
         context.DataSource.Id,

app/MindWork AI Studio/Tools/Services/Indexing/FileSourceIndexer.Watchers.cs

@@ -2,6 +2,7 @@ using System.Collections.Concurrent;
 
 using AIStudio.Settings;
 using AIStudio.Settings.DataModel;
+using AIStudio.Tools.Media;
 
 namespace AIStudio.Tools.Services.Indexing;
 
@@ -268,6 +269,14 @@ internal sealed partial class FileSourceIndexer
         if (Directory.Exists(path))
             return true;
 
+        //
+        // The Batch Processing assistant writes the transcript of a media file next to it. When
+        // the data source selects the media file itself, the transcript is no document of its
+        // own, so writing it must not start a run either:
+        //
+        if (MediaSidecarTranscripts.IsCoveredArtifact(path, selection))
+            return false;
+
         if (selection.Selects(path))
             return true;
 

app/MindWork AI Studio/Tools/Services/Indexing/FileSourceIndexer.cs

@@ -5,6 +5,7 @@ using AIStudio.Settings;
 using AIStudio.Settings.DataModel;
 using AIStudio.Tools.Databases.IndexStore;
 using AIStudio.Tools.Databases.VectorStore;
+using AIStudio.Tools.Media;
 using AIStudio.Tools.PluginSystem;
 using AIStudio.Tools.Rust;
 using AIStudio.Tools.Security;
@@ -32,9 +33,10 @@ namespace AIStudio.Tools.Services.Indexing;
 /// </remarks>
 /// <param name="settingsManager">The settings, read for whether local data sources refresh on their own.</param>
 /// <param name="rustService">The runtime, which extracts the text of the files.</param>
+/// <param name="mediaTranscriptionService">Transcribes selected audio and video files.</param>
 /// <param name="textChunker">Cuts the text of a file into chunks.</param>
 /// <param name="logger">The logger of the embedding service, so the log reads the same whoever writes it.</param>
-internal sealed partial class FileSourceIndexer(SettingsManager settingsManager, RustService rustService, TextChunker textChunker, ILogger logger) : IIndexedSourceIndexer
+internal sealed partial class FileSourceIndexer(SettingsManager settingsManager, RustService rustService, MediaTranscriptionService mediaTranscriptionService, TextChunker textChunker, ILogger logger) : IIndexedSourceIndexer
 {
     private const bool IMAGE_EMBEDDING_ENABLED = false;
     private const int MAX_LOGGED_EXCLUDED_FILE_EXAMPLES = 3;
@@ -45,12 +47,22 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
     {
         INDEXABLE,
         EXCLUDED,
-        MEDIA_NOT_SUPPORTED,
+        IMAGE_NOT_SUPPORTED,
+        TRANSCRIPTION_PROVIDER_MISSING,
+        TRANSCRIPTION_PROVIDER_NOT_ALLOWED,
         TOO_LARGE,
     }
 
     private sealed record DataSourceMetadataSnapshot(string SourceHash, IReadOnlyDictionary<string, string> FileHashes);
 
+    /// <summary>
+    /// What decides about the files of a data source while they are listed.
+    /// </summary>
+    /// <param name="Selection">The files of a folder data source, or null for a single file, which has no size limit.</param>
+    /// <param name="Manifest">What the index stores about the data source, or null when it does not matter.</param>
+    /// <param name="MediaTranscription">Which transcription provider may hear audio and video files, asked for only once such a file turns up.</param>
+    private sealed record InputFileRules(FolderFileSelection? Selection, DataSourceEmbeddingManifest? Manifest, Lazy<MediaTranscriptionAvailability> MediaTranscription);
+
     /// <inheritdoc />
     public bool Supports(IDataSourceBase dataSource) => dataSource is DataSourceLocalDirectory or DataSourceLocalFile;
 
@@ -66,7 +78,7 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         var manifest = context.Manifest;
 
         var enumerationStartedUtc = DateTimeOffset.UtcNow;
-        var inputFiles = this.GetInputFiles(dataSource);
+        var inputFiles = this.GetInputFiles(dataSource, manifest);
         var enumerationDuration = DateTimeOffset.UtcNow - enumerationStartedUtc;
         if (inputFiles.UnreachableRootReason is { } unreachableRootReason)
             return this.StopWithoutRoot(context, dataSource, unreachableRootReason);
@@ -133,6 +145,7 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
                 progress.RecordStillUnreadable(filePath, permanentFailure);
 
             await progress.CompleteRunAsync(metadataSnapshot.SourceHash, "data source finished after removing missing files", token);
+            this.CleanUpTranscripts(context, progress);
             return IndexedRunOutcome.DONE;
         }
 
@@ -181,7 +194,7 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
             var fingerprint = metadataSnapshot.FileHashes[file.FullName];
             var existingRecord = manifest.Files.GetValueOrDefault(file.FullName);
 
-            var document = this.CreateFileDocument(context, dataSource, file, fingerprint);
+            var document = this.CreateFileDocument(context, dataSource, file, fingerprint, null);
             var reportBlockProgress = progress.BeginDocument(document);
             var startedAtUtc = DateTimeOffset.UtcNow;
 
@@ -196,6 +209,14 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
                     ShortHash(fingerprint),
                     progress.DoneDocuments + 1,
                     totalFiles);
+
+                //
+                // Audio and video hold no text until they are transcribed. The document then reads
+                // its transcript instead, and its row knows which transcript that is:
+                //
+                if (PersistentMediaTranscript.IsMediaPath(file.FullName))
+                    document = this.CreateFileDocument(context, dataSource, file, fingerprint, await this.ReadOrCreateTranscriptAsync(dataSource, file.FullName, token));
+
                 var chunkCount = await context.IndexDocumentAsync(document, reportBlockProgress, token);
                 token.ThrowIfCancellationRequested();
                 var fingerprintAfterEmbedding = BuildFileMetadataHash(file);
@@ -203,6 +224,11 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
                     throw new IOException(string.Format(TB("The file '{0}' changed while it was being indexed. What was indexed of it is discarded, and the file is tried again during the next run."), file.FullName));
 
                 await progress.RecordDocumentIndexedAsync(document, chunkCount, existingRecord is null, token);
+
+                // The recording changed, so its old transcript is no longer what it says:
+                if (existingRecord?.TranscriptKey is { } previousTranscriptKey && !string.Equals(previousTranscriptKey, document.State.TranscriptKey, StringComparison.Ordinal))
+                    ForgetTranscript(DataSourceTranscriptStore.TryForDataSource(dataSource.Id), manifest, previousTranscriptKey, logger);
+
                 logger.LogInformation(
                     "Embedded file '{FilePath}' for data source '{DataSourceName}' ({DataSourceId}) successfully. Chunks={ChunkCount}, DurationMs={DurationMs}.",
                     file.FullName,
@@ -246,6 +272,7 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         }
 
         await progress.CompleteRunAsync(metadataSnapshot.SourceHash, "data source embedding run finished", token);
+        this.CleanUpTranscripts(context, progress);
         logger.LogInformation(
             "Finished background embeddings for data source '{DataSourceName}' ({DataSourceId}). RefreshMode={RefreshMode}, Embedded={EmbeddedFiles}, New={NewFiles}, Changed={ChangedFiles}, Skipped={SkippedFiles}, PermanentlySkipped={PermanentlySkippedFiles}, RemovedMissing={RemovedMissingFiles}, Failed={FailedFiles}, Total={TotalFiles}, SourceHashPrefix={SourceHashPrefix}.",
             dataSource.Name,
@@ -355,6 +382,79 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         return IndexedRunOutcome.DONE;
     }
 
+    /// <summary>
+    /// Deletes the transcripts which no file of the data source uses anymore, once a run got through all of it.
+    /// </summary>
+    /// <remarks>
+    /// Only a run without a failure knows every transcript which is still needed: a file which
+    /// failed may have its transcript already, and its next attempt must not pay for it again.
+    /// The transcript of a recording which is gone has to go as well, since it holds what was said.
+    /// </remarks>
+    /// <param name="context">The run.</param>
+    /// <param name="progress">How the run went.</param>
+    private void CleanUpTranscripts(IndexedRunContext context, DocumentRunProgress progress)
+    {
+        if (progress.FailedDocuments > 0)
+            return;
+
+        DeleteUnusedTranscripts(DataSourceTranscriptStore.TryForDataSource(context.DataSource.Id), context.Manifest, logger);
+    }
+
+    /// <summary>
+    /// Deletes every transcript of a data source which no indexed file uses, and the temporary files of interrupted writes.
+    /// </summary>
+    /// <param name="store">The transcripts of the data source, or null when there are none to clean up.</param>
+    /// <param name="manifest">What the index stores about the data source.</param>
+    /// <param name="logger">The logger.</param>
+    internal static void DeleteUnusedTranscripts(DataSourceTranscriptStore? store, DataSourceEmbeddingManifest manifest, ILogger logger)
+    {
+        if (store is null)
+            return;
+
+        try
+        {
+            var usedKeys = manifest.Files.Values
+                .Select(record => record.TranscriptKey)
+                .OfType<string>()
+                .ToHashSet(StringComparer.Ordinal);
+
+            var deleted = store.ListKeys().Count(key => !usedKeys.Contains(key) && store.Delete(key));
+            deleted += store.DeleteTemporaryFiles();
+            if (deleted > 0)
+                logger.LogInformation("Removed {DeletedTranscripts} transcript file(s) which no file of the data source uses anymore.", deleted);
+        }
+        catch (Exception exception)
+        {
+            logger.LogWarning(exception, "Could not remove the transcripts which no file of the data source uses anymore. The next complete run tries again.");
+        }
+    }
+
+    /// <summary>
+    /// Deletes the transcript with the given key, unless another file of the data source still uses it.
+    /// </summary>
+    /// <remarks>
+    /// Two recordings with the same content share one transcript, cf. DataSourceTranscriptStore.
+    /// </remarks>
+    /// <param name="store">The transcripts of the data source, or null when there are none to clean up.</param>
+    /// <param name="manifest">What the index stores about the data source, without the file the transcript belonged to.</param>
+    /// <param name="key">The key of the transcript, or null when the file had none.</param>
+    /// <param name="logger">The logger.</param>
+    internal static void ForgetTranscript(DataSourceTranscriptStore? store, DataSourceEmbeddingManifest manifest, string? key, ILogger logger)
+    {
+        if (store is null || string.IsNullOrWhiteSpace(key) || manifest.Files.Values.Any(record => string.Equals(record.TranscriptKey, key, StringComparison.Ordinal)))
+            return;
+
+        try
+        {
+            if (store.Delete(key))
+                logger.LogInformation("Removed the transcript '{TranscriptKey}', since no file of the data source uses it anymore.", key);
+        }
+        catch (Exception exception)
+        {
+            logger.LogWarning(exception, "Could not remove the transcript '{TranscriptKey}'. The next complete run tries again.", key);
+        }
+    }
+
     private async Task<int> RemoveMissingFileEmbeddingsAsync(IndexedRunContext context, FileEnumerationResult inputFiles, CancellationToken token)
     {
         var manifest = context.Manifest;
@@ -363,7 +463,9 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         {
             await context.DeleteDocumentPointsAsync(removedFilePath, token);
             await context.IndexStore.DeleteFileAsync(context.DataSource.Id, removedFilePath, token);
+            var removedTranscriptKey = manifest.Files.GetValueOrDefault(removedFilePath)?.TranscriptKey;
             manifest.Files.Remove(removedFilePath);
+            ForgetTranscript(DataSourceTranscriptStore.TryForDataSource(context.DataSource.Id), manifest, removedTranscriptKey, logger);
             removedFiles++;
             logger.LogInformation(
                 "Removed stale embeddings for deleted file '{FilePath}' from data source '{DataSourceName}' ({DataSourceId}).",
@@ -487,19 +589,123 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
             : string.Join("; ", reasons);
     }
 
-    private async IAsyncEnumerable<EmbeddingChunk> StreamEmbeddingChunksAsync(string filePath, IDataSource dataSource, EmbeddingProvider embeddingProvider, PromptInjectionReportingScope reportingScope, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken token)
+    private async IAsyncEnumerable<EmbeddingChunk> StreamEmbeddingChunksAsync(string filePath, MediaTranscriptSlot? transcript, IDataSource dataSource, EmbeddingProvider embeddingProvider, PromptInjectionReportingScope reportingScope, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken token)
     {
         var options = DataSourceEmbeddingService.GetChunkingOptions(dataSource, embeddingProvider);
-        var strategy = TextChunker.GetStrategyForFile(filePath);
-        var content = await ExtractedFileText.ReadAsync(rustService, filePath, embeddingProvider, null, reportingScope, token);
+
+        //
+        // An audio or video file is read through its transcript. The runtime reads the transcript
+        // like every other document, so it passes the same prompt injection filter, and a notice
+        // names the media file rather than the transcript below the data directory:
+        //
+        var contentPath = transcript?.Path ?? filePath;
+        PromptInjectionSource? reportAs = transcript is null ? null : PromptInjectionSource.FileContent(filePath);
+        var strategy = TextChunker.GetStrategyForFile(contentPath);
+        var content = await ExtractedFileText.ReadAsync(rustService, contentPath, embeddingProvider, reportAs, reportingScope, token);
 
         await foreach (var chunk in textChunker.SplitAsync(content, strategy, options, embeddingProvider, token))
             yield return chunk;
     }
 
-    internal FileEnumerationResult GetInputFiles(IDataSource dataSource)
+    /// <summary>
+    /// Returns the transcript of an audio or video file, transcribing the file only when the data source holds no transcript of its content yet.
+    /// </summary>
+    /// <remarks>
+    /// The provider is checked against the data source once more, right before the upload: the
+    /// settings may have changed since the files were listed. A transcript which exists is used
+    /// without any provider, since nothing leaves the computer for it.<br/><br/>
+    ///
+    /// A transcription which cannot succeed for this file, such as one without text, is recorded
+    /// for good, so the file is not paid for again until it changes.
+    /// </remarks>
+    /// <param name="dataSource">The data source.</param>
+    /// <param name="mediaPath">The audio or video file.</param>
+    /// <param name="token">The cancellation token.</param>
+    /// <returns>Where the transcript is.</returns>
+    private async Task<MediaTranscriptSlot> ReadOrCreateTranscriptAsync(IDataSource dataSource, string mediaPath, CancellationToken token)
+    {
+        var provider = this.GetMediaTranscriptionAvailability(dataSource).Provider;
+        var transcript = await PersistentMediaTranscript.ReadOrCreateAsync(DataSourceTranscriptStore.ForDataSource(dataSource.Id), mediaPath, provider, mediaTranscriptionService.TranscribeAsync, logger, token);
+        return GetTranscriptOrThrow(transcript, token);
+    }
+
+    /// <summary>
+    /// Returns the transcript, or throws what tells the run how to treat the media file without one.
+    /// </summary>
+    /// <remarks>
+    /// A FileExtractionException records the file for good, until it changes; any other exception
+    /// lets the next pass try again. A transcription without text, a file which the media pipeline
+    /// cannot read, and a file which the transcription provider refused would fail the same way
+    /// every time, and every attempt would cost money or another upload.
+    /// </remarks>
+    /// <param name="transcript">The outcome of the request for the transcript.</param>
+    /// <param name="token">The cancellation token of the run.</param>
+    /// <returns>Where the transcript is.</returns>
+    internal static MediaTranscriptSlot GetTranscriptOrThrow(PersistentMediaTranscriptResult transcript, CancellationToken token) => transcript.Status switch
+    {
+        PersistentMediaTranscriptStatus.READY => new(transcript.TranscriptPath, transcript.Key),
+        PersistentMediaTranscriptStatus.CANCELLED => throw new OperationCanceledException(token),
+        PersistentMediaTranscriptStatus.EMPTY or PersistentMediaTranscriptStatus.NO_AUDIBLE_SIGNAL => throw new FileExtractionException(FileExtractionErrorCode.NO_CONTENT, transcript.UserMessage),
+        PersistentMediaTranscriptStatus.TRANSCRIPTION_FAILED when IsPermanentMediaFailure(transcript.ErrorCode) => throw new FileExtractionException(FileExtractionErrorCode.MEDIA_PROCESSING_FAILED, transcript.UserMessage),
+        PersistentMediaTranscriptStatus.REJECTED => throw new FileExtractionException(FileExtractionErrorCode.MEDIA_PROCESSING_FAILED, transcript.UserMessage),
+        _ => throw new IOException(transcript.UserMessage),
+    };
+
+    /// <summary>
+    /// Which transcription provider may hear the audio and video files of a data source right now.
+    /// </summary>
+    /// <remarks>
+    /// The transcription provider receives the content of the data source just like the embedding
+    /// provider, so it has to meet the confidence level of the data source as well, cf.
+    /// DataSourceEmbeddingService.AllowsTranscription. A data source without a confidence level
+    /// of its own is never sent anywhere.
+    /// </remarks>
+    /// <param name="dataSource">The data source.</param>
+    /// <returns>The provider, or why there is none.</returns>
+    private MediaTranscriptionAvailability GetMediaTranscriptionAvailability(IDataSource dataSource)
+    {
+        var provider = mediaTranscriptionService.GetUsableProvider();
+        if (provider is null)
+            return MediaTranscriptionAvailability.MISSING;
+
+        var providerConfidence = provider.GetConfidenceLevel(settingsManager);
+        if (dataSource is IIndexedDataSource indexedDataSource && DataSourceEmbeddingService.AllowsTranscription(indexedDataSource, providerConfidence))
+            return MediaTranscriptionAvailability.Allowed(provider);
+
+        logger.LogInformation(
+            "The transcription provider '{ProviderName}' may not hear the audio and video files of data source '{DataSourceName}' ({DataSourceId}): the data source asks for the confidence level {RequiredConfidence}, while the provider has {ProviderConfidence}.",
+            provider.Name,
+            dataSource.Name,
+            dataSource.Id,
+            (dataSource as IIndexedDataSource)?.ConfidenceLevel,
+            providerConfidence);
+
+        return MediaTranscriptionAvailability.NOT_ALLOWED;
+    }
+
+    private static bool IsPermanentMediaFailure(MediaJobErrorCode? code) => code is
+        MediaJobErrorCode.UNKNOWN_FORMAT
+        or MediaJobErrorCode.UNSAFE_FILE
+        or MediaJobErrorCode.NOT_MEDIA
+        or MediaJobErrorCode.UNSUPPORTED_CONTAINER
+        or MediaJobErrorCode.NO_AUDIO_TRACK
+        or MediaJobErrorCode.UNSUPPORTED_CODEC
+        or MediaJobErrorCode.INVALID_AUDIO_PARAMETERS
+        or MediaJobErrorCode.INVALID_OPUS_HEADER
+        or MediaJobErrorCode.UNSUPPORTED_OPUS_MAPPING
+        or MediaJobErrorCode.DAMAGED_CONTAINER;
+
+    /// <summary>
+    /// Lists the files of a data source and decides what a run does with each of them.
+    /// </summary>
+    /// <param name="dataSource">The data source.</param>
+    /// <param name="manifest">What the index stores about the data source, or null when it does not matter.</param>
+    /// <param name="mediaTranscription">Which transcription provider may hear its audio and video files, or null to ask the settings once a media file turns up.</param>
+    /// <returns>The files, and those which were left out.</returns>
+    internal FileEnumerationResult GetInputFiles(IDataSource dataSource, DataSourceEmbeddingManifest? manifest = null, MediaTranscriptionAvailability? mediaTranscription = null)
     {
         var result = new FileEnumerationResult();
+        var mediaTranscriptionAvailability = new Lazy<MediaTranscriptionAvailability>(() => mediaTranscription ?? this.GetMediaTranscriptionAvailability(dataSource));
 
         switch (dataSource)
         {
@@ -507,13 +713,13 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
                 var file = new FileInfo(localFile.FilePath);
 
                 // No size limit: the user chose this very file, cf. FolderFileSelection.IsTooLarge.
-                if (this.AddInputFile(file, null, result) is RagFileIndexingDecision.EXCLUDED)
+                if (this.AddInputFile(file, new InputFileRules(null, manifest, mediaTranscriptionAvailability), result) is RagFileIndexingDecision.EXCLUDED)
                     logger.LogDebug("Skipping excluded file '{FilePath}' while indexing.", file.FullName);
 
                 return result;
 
             case DataSourceLocalDirectory localDirectory when Directory.Exists(localDirectory.Path):
-                this.EnumerateAccessibleFiles(localDirectory, result);
+                this.EnumerateAccessibleFiles(localDirectory, manifest, mediaTranscriptionAvailability, result);
                 if (result.UnreadableDirectories.Contains(localDirectory.Path))
                     result.UnreachableRootReason = string.Format(TB("The folder '{0}' could not be opened. Please check whether you are allowed to read it. Nothing was removed from the index."), localDirectory.Path);
 
@@ -537,9 +743,10 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         return result;
     }
 
-    private void EnumerateAccessibleFiles(DataSourceLocalDirectory dataSource, FileEnumerationResult result)
+    private void EnumerateAccessibleFiles(DataSourceLocalDirectory dataSource, DataSourceEmbeddingManifest? manifest, Lazy<MediaTranscriptionAvailability> mediaTranscription, FileEnumerationResult result)
     {
         var selection = FolderFileSelection.Of(dataSource);
+        var rules = new InputFileRules(selection, manifest, mediaTranscription);
 
         //
         // Every log line travels to the runtime as a request of its own. A folder holding many
@@ -580,7 +787,17 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
                 continue;
             }
 
-            if (this.AddInputFile(fileInfo, selection, result) is not RagFileIndexingDecision.EXCLUDED)
+            //
+            // The transcript which the Batch Processing assistant wrote next to a selected media
+            // file holds the text the data source gets from the media file itself:
+            //
+            if (MediaSidecarTranscripts.IsCoveredArtifact(fileInfo.FullName, selection))
+            {
+                logger.LogDebug("Skipping the transcript '{FilePath}', because its media file is indexed as the document.", fileInfo.FullName);
+                continue;
+            }
+
+            if (this.AddInputFile(fileInfo, rules, result) is not RagFileIndexingDecision.EXCLUDED)
                 continue;
 
             excludedFiles++;
@@ -593,11 +810,11 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
     }
 
     /// <param name="file">The file.</param>
-    /// <param name="selection">The files of a folder data source, or null for a single file, which has no size limit.</param>
+    /// <param name="rules">What decides about the files of the data source.</param>
     /// <param name="result">Where the file goes, if anywhere.</param>
-    private RagFileIndexingDecision AddInputFile(FileInfo file, FolderFileSelection? selection, FileEnumerationResult result)
+    private RagFileIndexingDecision AddInputFile(FileInfo file, InputFileRules rules, FileEnumerationResult result)
     {
-        var decision = this.GetRagFileIndexingDecision(file, selection);
+        var decision = this.GetRagFileIndexingDecision(file, rules);
         switch (decision)
         {
             case RagFileIndexingDecision.INDEXABLE:
@@ -607,8 +824,16 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
             case RagFileIndexingDecision.EXCLUDED:
                 break;
 
-            case RagFileIndexingDecision.MEDIA_NOT_SUPPORTED:
-                result.AddIgnoredFile(file.FullName, DataSourceEmbeddingIgnoreReason.MEDIA_NOT_SUPPORTED);
+            case RagFileIndexingDecision.IMAGE_NOT_SUPPORTED:
+                result.AddIgnoredFile(file.FullName, DataSourceEmbeddingIgnoreReason.IMAGE_NOT_SUPPORTED);
+                break;
+
+            case RagFileIndexingDecision.TRANSCRIPTION_PROVIDER_MISSING:
+                result.AddIgnoredFile(file.FullName, DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_MISSING);
+                break;
+
+            case RagFileIndexingDecision.TRANSCRIPTION_PROVIDER_NOT_ALLOWED:
+                result.AddIgnoredFile(file.FullName, DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_NOT_ALLOWED);
                 break;
 
             case RagFileIndexingDecision.TOO_LARGE:
@@ -630,24 +855,24 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         return FileTypes.IsAllowedPath(filePath, FileTypes.IMAGE);
     }
 
-    private RagFileIndexingDecision GetRagFileIndexingDecision(FileInfo file, FolderFileSelection? selection)
+    private RagFileIndexingDecision GetRagFileIndexingDecision(FileInfo file, InputFileRules rules)
     {
         if (this.IsSkippedRagFile(file))
             return RagFileIndexingDecision.EXCLUDED;
 
         if (!IMAGE_EMBEDDING_ENABLED && this.IsImageFilePath(file.FullName))
-            return RagFileIndexingDecision.MEDIA_NOT_SUPPORTED;
+            return RagFileIndexingDecision.IMAGE_NOT_SUPPORTED;
 
         //
-        // Audio and video hold no text until they are transcribed, and data sources do not
-        // transcribe them yet:
+        // Before any transcription: a video of several gigabytes is left out like every other
+        // file above the limit, rather than sent to the transcription provider.
         //
-        if (FileTypes.IsAllowedPath(file.FullName, FileTypes.AUDIO, FileTypes.VIDEO))
-            return RagFileIndexingDecision.MEDIA_NOT_SUPPORTED;
-
-        if (selection?.IsTooLarge(file) is true)
+        if (rules.Selection?.IsTooLarge(file) is true)
             return RagFileIndexingDecision.TOO_LARGE;
 
+        if (PersistentMediaTranscript.IsMediaPath(file.FullName))
+            return GetMediaIndexingDecision(file, rules);
+
         // A directory source reaches this point only after its user-configured pattern selected
         // the file. A single-file source was validated before it was stored. Extraction is the
         // authoritative capability check and records an unreadable selected file through the
@@ -655,6 +880,39 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         return RagFileIndexingDecision.INDEXABLE;
     }
 
+    /// <summary>
+    /// Decides about an audio or video file, which holds no text until it is transcribed.
+    /// </summary>
+    /// <remarks>
+    /// A media file which the index holds unchanged needs no transcript in this run, nor does one
+    /// which failed for good before: neither is read. A missing transcription provider, or one which
+    /// the data source no longer allows, therefore takes nothing out of the index. Every other media
+    /// file needs a provider which may hear it, unless the data source has its transcript already;
+    /// that is only known once the file is read, so such a file waits for the provider as well.
+    /// </remarks>
+    /// <param name="file">The audio or video file.</param>
+    /// <param name="rules">What decides about the files of the data source.</param>
+    /// <returns>INDEXABLE, or why the file is left out.</returns>
+    private static RagFileIndexingDecision GetMediaIndexingDecision(FileInfo file, InputFileRules rules)
+    {
+        if (rules.Manifest is { } manifest)
+        {
+            var fingerprint = BuildFileMetadataHash(file);
+            if (manifest.Files.TryGetValue(file.FullName, out var existingRecord) && string.Equals(existingRecord.Fingerprint, fingerprint, StringComparison.Ordinal))
+                return RagFileIndexingDecision.INDEXABLE;
+
+            if (manifest.PermanentFailures.TryGetValue(file.FullName, out var permanentFailure) && string.Equals(permanentFailure.Fingerprint, fingerprint, StringComparison.Ordinal))
+                return RagFileIndexingDecision.INDEXABLE;
+        }
+
+        return rules.MediaTranscription.Value.IgnoreReason switch
+        {
+            null => RagFileIndexingDecision.INDEXABLE,
+            DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_NOT_ALLOWED => RagFileIndexingDecision.TRANSCRIPTION_PROVIDER_NOT_ALLOWED,
+            _ => RagFileIndexingDecision.TRANSCRIPTION_PROVIDER_MISSING,
+        };
+    }
+
     private bool IsSkippedRagFile(FileInfo file)
     {
         if (FileExclusions.IsAlwaysExcludedFile(file.Name))
@@ -731,7 +989,7 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
         return BuildMetadataHash(parts);
     }
 
-    private static string BuildFileMetadataHash(FileInfo file)
+    internal static string BuildFileMetadataHash(FileInfo file)
     {
         file.Refresh();
         if (!file.Exists)
@@ -774,12 +1032,13 @@ internal sealed partial class FileSourceIndexer(SettingsManager settingsManager,
     /// <param name="dataSource">The data source the file belongs to.</param>
     /// <param name="file">The file.</param>
     /// <param name="fingerprint">The fingerprint of the file as it is about to be read.</param>
+    /// <param name="transcript">The transcript an audio or video file is read through, or null for every other file.</param>
     /// <returns>The document.</returns>
-    private EmbeddingDocument CreateFileDocument(IndexedRunContext context, IDataSource dataSource, FileInfo file, string fingerprint) => new(
+    private EmbeddingDocument CreateFileDocument(IndexedRunContext context, IDataSource dataSource, FileInfo file, string fingerprint, MediaTranscriptSlot? transcript) => new(
         file.FullName,
-        this.CreateEmbeddingStateFile(dataSource, file, fingerprint, 0, DateTimeOffset.UtcNow),
+        this.CreateEmbeddingStateFile(dataSource, file, fingerprint, 0, DateTimeOffset.UtcNow) with { TranscriptKey = transcript?.Key },
         file.Name,
-        token => this.StreamEmbeddingChunksAsync(file.FullName, dataSource, context.EmbeddingProvider, context.PromptInjectionScope, token));
+        token => this.StreamEmbeddingChunksAsync(file.FullName, transcript, dataSource, context.EmbeddingProvider, context.PromptInjectionScope, token));
 
     private EmbeddingStateFile CreateEmbeddingStateFile(IDataSource dataSource, FileInfo file, string fingerprint, int chunkCount, DateTimeOffset embeddedAtUtc)
     {

app/MindWork AI Studio/Tools/Services/Indexing/MediaTranscriptionAvailability.cs

@@ -0,0 +1,28 @@
+using AIStudio.Settings;
+
+namespace AIStudio.Tools.Services.Indexing;
+
+/// <summary>
+/// Which transcription provider may hear the audio and video files of a data source.
+/// </summary>
+/// <param name="Provider">The provider, or null when none may.</param>
+/// <param name="IgnoreReason">Why audio and video files without a transcript are left out when no provider may hear them; null when there is a provider.</param>
+internal sealed record MediaTranscriptionAvailability(TranscriptionProvider? Provider, DataSourceEmbeddingIgnoreReason? IgnoreReason)
+{
+    /// <summary>
+    /// No usable transcription provider is configured.
+    /// </summary>
+    public static readonly MediaTranscriptionAvailability MISSING = new(null, DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_MISSING);
+
+    /// <summary>
+    /// The configured transcription provider falls short of the confidence level of the data source.
+    /// </summary>
+    public static readonly MediaTranscriptionAvailability NOT_ALLOWED = new(null, DataSourceEmbeddingIgnoreReason.TRANSCRIPTION_PROVIDER_NOT_ALLOWED);
+
+    /// <summary>
+    /// The given provider may hear the media files.
+    /// </summary>
+    /// <param name="provider">The provider.</param>
+    /// <returns>The availability.</returns>
+    public static MediaTranscriptionAvailability Allowed(TranscriptionProvider provider) => new(provider, null);
+}

app/MindWork AI Studio/Tools/Services/MediaTranscriptionService.cs

@@ -63,7 +63,7 @@ public sealed class MediaTranscriptionService(
     }
 
     /// <summary>Gets whether the currently configured transcription provider can be used.</summary>
-    public bool HasUsableTranscriptionProvider => this.ResolveProvider() is not null;
+    public bool HasUsableTranscriptionProvider => this.GetUsableProvider() is not null;
 
     /// <summary>Gets the last retained state for one owner.</summary>
     public MediaImportSnapshot? GetSnapshot(MediaImportOwner owner)
@@ -411,14 +411,31 @@ public sealed class MediaTranscriptionService(
     /// <param name="mediaPath">Audio or video file path.</param>
     /// <param name="token">Caller cancellation token.</param>
     /// <returns>A typed terminal result.</returns>
-    public async Task<MediaTranscriptionResult> TranscribeAsync(string mediaPath, CancellationToken token = default)
+    public Task<MediaTranscriptionResult> TranscribeAsync(string mediaPath, CancellationToken token = default) => this.TranscribeWithoutImportAsync(mediaPath, null, token);
+
+    /// <summary>
+    /// Transcribes an audio or video file with exactly the given provider, without starting a visible import operation.
+    /// </summary>
+    /// <remarks>
+    /// For callers which checked the provider against rules of their own, such as the confidence
+    /// level of a data source. The provider is used as given and not resolved from the settings
+    /// again, so a change of the settings between that check and the upload cannot send the media
+    /// to another provider.
+    /// </remarks>
+    /// <param name="mediaPath">Audio or video file path.</param>
+    /// <param name="provider">The transcription provider the caller checked.</param>
+    /// <param name="token">Caller cancellation token.</param>
+    /// <returns>A typed terminal result.</returns>
+    public Task<MediaTranscriptionResult> TranscribeAsync(string mediaPath, TranscriptionProvider provider, CancellationToken token = default) => this.TranscribeWithoutImportAsync(mediaPath, provider, token);
+
+    private async Task<MediaTranscriptionResult> TranscribeWithoutImportAsync(string mediaPath, TranscriptionProvider? provider, CancellationToken token)
     {
         this.ThrowIfDisposed();
         var operation = this.CreateOperation(null, token);
-        
+
         try
         {
-            return await this.TranscribeCoreAsync(mediaPath, operation, updateImportState: false);
+            return await this.TranscribeCoreAsync(mediaPath, operation, updateImportState: false, provider);
         }
         finally
         {
@@ -458,8 +475,9 @@ public sealed class MediaTranscriptionService(
     /// <param name="mediaPath">Source media path.</param>
     /// <param name="operation">Operation-specific cancellation and Rust-job state.</param>
     /// <param name="updateImportState">Whether progress belongs to the visible import lane.</param>
+    /// <param name="checkedProvider">The provider a caller checked itself, or null for the configured one.</param>
     /// <returns>A typed terminal result.</returns>
-    private async Task<MediaTranscriptionResult> TranscribeCoreAsync(string mediaPath, MediaOperation operation, bool updateImportState)
+    private async Task<MediaTranscriptionResult> TranscribeCoreAsync(string mediaPath, MediaOperation operation, bool updateImportState, TranscriptionProvider? checkedProvider = null)
     {
         var normalizedPath = Path.Combine(Path.GetTempPath(), "mindwork-ai-studio-media", $"{operation.Id:N}.webm");
         Directory.CreateDirectory(Path.GetDirectoryName(normalizedPath)!);
@@ -497,7 +515,7 @@ public sealed class MediaTranscriptionService(
                 return MediaTranscriptionResult.NoAudibleSignal(TB("The audio track contains no audible signal, so there is nothing to transcribe."));
             }
 
-            var providerSettings = this.ResolveProvider();
+            var providerSettings = checkedProvider ?? this.GetUsableProvider();
             if (providerSettings is null)
                 return MediaTranscriptionResult.Failed(TB("No usable transcription provider is configured."));
 
@@ -530,16 +548,20 @@ public sealed class MediaTranscriptionService(
                     "The transcription provider failed for '{FileName}' (operation {OperationId}): {Diagnostic}",
                     fileName,
                     operation.Id,
-                    providerResult.ErrorMessage);
+                    string.IsNullOrWhiteSpace(providerResult.ErrorMessage) ? "<empty>" : providerResult.ErrorMessage);
 
                 //
                 // When the provider told us why it failed, the user gets to read it. Only that
                 // message says whether to wait, to check the API key, or to ask the provider for
                 // a format it can read:
                 //
-                return MediaTranscriptionResult.Failed(string.IsNullOrWhiteSpace(providerResult.ErrorMessage)
+                var failureMessage = string.IsNullOrWhiteSpace(providerResult.ErrorMessage)
                     ? TB("The transcription provider could not transcribe the media file.")
-                    : providerResult.ErrorMessage);
+                    : providerResult.ErrorMessage;
+
+                return providerResult.FileRejected
+                    ? MediaTranscriptionResult.Rejected(failureMessage)
+                    : MediaTranscriptionResult.Failed(failureMessage);
             }
 
             return MediaTranscriptionResult.Succeeded(providerResult.Text.Trim());
@@ -719,7 +741,12 @@ public sealed class MediaTranscriptionService(
     }
 
     /// <summary>Resolves the configured provider after confidence validation.</summary>
-    private TranscriptionProvider? ResolveProvider()
+    /// <remarks>
+    /// Checks the global minimum confidence only. A caller with rules of its own, such as the
+    /// confidence level of a data source, checks the provider against them as well.
+    /// </remarks>
+    /// <returns>The configured provider, or null when none is configured or it falls short of the global minimum.</returns>
+    public TranscriptionProvider? GetUsableProvider()
     {
         var providerId = settingsManager.ConfigurationData.App.UseTranscriptionProvider;
         if (string.IsNullOrWhiteSpace(providerId))
@@ -735,6 +762,19 @@ public sealed class MediaTranscriptionService(
             : null;
     }
 
+    /// <summary>
+    /// The configured provider, when it may also hear the audio and video files of the given data source.
+    /// </summary>
+    /// <param name="dataSource">The data source, with the confidence level it asks for.</param>
+    /// <returns>The provider, or null when none is configured or it falls short of the global minimum or of the data source.</returns>
+    public TranscriptionProvider? GetUsableProvider(IIndexedDataSource dataSource)
+    {
+        var provider = this.GetUsableProvider();
+        return provider is not null && DataSourceEmbeddingService.AllowsTranscription(dataSource, provider.GetConfidenceLevel(settingsManager))
+            ? provider
+            : null;
+    }
+
     /// <summary>Creates and registers operation-owned cancellation state.</summary>
     /// <param name="target">Optional visible media import target.</param>
     /// <param name="token">Caller token linked to the operation.</param>