OpenSubsonic: getPodcastEpisode, topSongsByArtistId, transcodeOffset (real ffmpeg seek)

internal/subsonic/media.go

@@ -17,6 +17,7 @@ import (
 )
 
 func init() {
+	registerExtension("transcodeOffset", 1)
 	register("stream", handleStream)
 	register("download", handleDownload)
 	register("getCoverArt", handleGetCoverArt)
@@ -75,14 +76,22 @@ func handleStream(rc *Context) *apiError {
 
 	rc.Handled = true
 
-	// format=raw explicitly forces the original bytes. Otherwise,
-	// transcode only if the client actually asked for something the
-	// source doesn't already satisfy: a specific format, or a bitrate
-	// cap below the source's own bitrate.
+	// format=raw explicitly forces the original bytes (timeOffset can't
+	// be honored in that case — a direct byte stream has no way to seek
+	// by time — so it's silently ignored, matching "raw" meaning
+	// "disable transcoding"). Otherwise, transcode whenever the client
+	// asked for something the source can't satisfy by itself: a
+	// specific format, a bitrate cap below the source's own bitrate, or
+	// (the transcodeOffset extension) a start offset — direct-serving
+	// bytes has no notion of "start at N seconds", only real
+	// transcoding with an ffmpeg seek can do that.
 	needsTranscode := formatParam != "" && formatParam != "raw"
 	if maxBitRate > 0 && (mf.BitrateKbps == 0 || maxBitRate < mf.BitrateKbps) {
 		needsTranscode = true
 	}
+	if timeOffset > 0 && formatParam != "raw" {
+		needsTranscode = true
+	}
 	if !needsTranscode {
 		if err := streaming.ServeFile(rc.W, rc.R, absPath, mf.RelativePath); err != nil {
 			http.Error(rc.W, "could not read media file", http.StatusInternalServerError)