Added per-codec bitstream filter support to audio codecs.

core/transcoder/audiocodec.go

@@ -11,6 +11,7 @@ type AudioCodec interface {
 	Name() string
 	DisplayName() string
 	FFmpegEncoderName() string
+	BitstreamFilters() []string
 }
 
 // AACCodec implements AudioCodec for AAC audio.
@@ -30,6 +31,12 @@ func (c *AACCodec) FFmpegEncoderName() string {
 	return aacFFmpegEncoder
 }
 
+func (c *AACCodec) BitstreamFilters() []string {
+	return []string{
+		// "aac_adtstoasc", // Required for fMP4 segments, not needed yet.
+	}
+}
+
 var audioCodecRegistry = map[string]AudioCodec{
 	audioCodecAAC: &AACCodec{},
 }

core/transcoder/transcoder.go

@@ -469,11 +469,17 @@ func (v *HLSVariant) getAudioQualityString() []string {
 		}
 	}
 
-	return []string{
+	flags := []string{
 		"-map", "a:0?",
 		fmt.Sprintf("-c:a:%d", v.index), v.audioCodec.FFmpegEncoderName(),
 		fmt.Sprintf("-b:a:%d", v.index), v.audioBitrate,
 	}
+
+	for _, bsf := range v.audioCodec.BitstreamFilters() {
+		flags = append(flags, fmt.Sprintf("-bsf:a:%d", v.index), bsf)
+	}
+
+	return flags
 }
 
 // AddVariant adds a new HLS variant to include in the output.