No sound when playing transcoded Video with FLAC audio stream

[b-m-f]

It seems to be related to jellyfin/jellyfin#8224 (comment).

Playing any video file - transcoded - will result in no audio when the FLAC track is selected.

This is not an issue when direct-playing the video file. All audio codecs work fine then.
Also all other clients tested by me:

• Android (web and native player)
• web player
• Linux desktop app
• IOS

Work without the audio dropping.

[xingoxu]

Same here. I've enabled forced transcoding and chose the aac / ac3 for audio codec but I see ffmpeg command still uses flac.

jellyfin-1  | [17:45:51] [INF] [78] MediaBrowser.MediaEncoding.Transcoding.TranscodeManager: /usr/lib/jellyfin-ffmpeg/ffmpeg -analyzeduration 200M -probesize 1G -init_hw_device vaapi=va:,kernel_driver=i915,driver=iHD -init_hw_device qsv=qs@va -filter_hw_device qs -noautorotate -i file:"/data/Anime/Buddy Complex/Season 1/S01E01.mkv" -map_metadata -1 -map_chapters -1 -threads 0 -map 0:0 -map 0:1 -map -0:s -codec:v:0 h264_qsv -preset veryfast -look_ahead 0 -b:v 12021144 -maxrate 12021144 -bufsize 24042288 -profile:v:0 high -level 50 -g:v:0 72 -keyint_min:v:0 72 -vf "setparams=color_primaries=bt709:color_trc=bt709:colorspace=bt709,scale=trunc(min(max(iw\,ih*a)\,min(2841\,1344*a))/2)*2:trunc(min(max(iw/a\,ih)\,min(2841/a\,1344))/2)*2,format=nv12" -codec:a:0 flac -ac 2 -ar 48000 -copyts -avoid_negative_ts disabled -max_muxing_queue_size 2048 -f hls -max_delay 5000000 -hls_time 3 -hls_segment_type mpegts -start_number 0 -hls_segment_filename "/cache/transcode/39d9628a7c81be3da744e6f9b0d35989%d.ts" -hls_playlist_type vod -hls_list_size 0 -y "/cache/transcode/39d9628a7c81be3da744e6f9b0d35989.m3u8"

[Nocifer]

Gah, this issue has been my single personal annoyance with Jellyfin for years now. I was under the impression that it's a Jellyfin server issue, but the people over at Jellyfin server have recently stated that this should not be an issue on their end (which is supported by the fact that other clients do not have this issue), so I guess the problem is with the Jellyfin Kodi plugin after all.

Skimming through the code for a whole of 5 minutes I stumbled on this (in helper/playutils.py):

    def get_transcoding_audio_codec(self):
        codecs = ["aac", "mp3", "ac3", "opus", "flac", "vorbis"]

...followed by this:

    "TranscodingProfiles": [
                {
                    "Type": "Video",
                    "Container": "m3u8",
                    "AudioCodec": self.get_transcoding_audio_codec(),
                    ...

Now, if I'm getting this right (and I could very well be way off, seeing as I've pretty much only read this part of the code) it seems like the plugin advertises the audio formats it supports for transcoding into as the above codecs array, which includes FLAC. And if my understanding is right, then during transcoding we should never be attempting to use FLAC as the audio codec, even if the device supports it natively during direct play.

So perhaps if FLAC were to be removed from this array, the issue could be fixed?

[oddstr13]

jellyfin-kodi/jellyfin_kodi/helper/playutils.py

Lines 406 to 413 in 6140ea8

	def get_transcoding_audio_codec(self):
	codecs = ["aac", "mp3", "ac3", "opus", "flac", "vorbis"]
	preferred = settings("audioPreferredCodec").lower()
	if preferred in codecs:
	codecs.insert(0, codecs.pop(codecs.index(preferred)))
	return ",".join(codecs)

Removing flac from that list would likely cause it to get transcoded into aac (by default – audioPreferredCodec setting)

Video codecs have a few settings to force transcoding of mp2, hevc, av1 and vc1
Adding similar settings for audio codecs would be feasible

jellyfin-kodi/jellyfin_kodi/helper/playutils.py

Lines 385 to 404 in 6140ea8

	def get_transcoding_video_codec(self):
	codecs = ["h264", "mpeg4", "mpeg2video", "vc1"]
	if settings("videoPreferredCodec") == "H265/HEVC":
	codecs.insert(0, "hevc")
	elif not settings("transcode_h265.bool"):
	codecs.insert(1, "hevc")
	if settings("videoPreferredCodec") == "AV1":
	codecs.insert(0, "av1")
	elif not settings("transcode_av1.bool"):
	codecs.append("av1")
	if settings("transcode_mpeg2.bool"):
	codecs.remove("mpeg2video")
	if settings("transcode_vc1.bool"):
	codecs.remove("vc1")
	return ",".join(codecs)

[Nocifer]

Yeah, so it works more or less as I Imagined. If everything stays at the default state, then during transcoding the audio will get transcoded to the widely compatible AAC by default (with a list of further possible candidates), just like video will get transcoded to the widely compatible H.264 by default (with, again, a list of further candidates).

For the video part, the user can opt to select something else in the settings as the preferred video codec to transcode into, and the same functionality could (and should) be added to the audio part, because it's very useful (for example, some specific audio format could be supported for pass-through on some specific sound device, although that's often enough the case with the default AAC).

But aside from all that, this specific issue arises from the fact that FLAC is also included in that list of possible format candidates, so when the system tries to transcode a media file which contains FLAC audio, the audio part is considered as already compatible and so is left untouched, and is then (attempted to be) muxed into the TS container with the transcoded video stream, but the TS container doesn't support FLAC audio, which leads to the issue.

So yes, I think the proper solution here should be to remove FLAC from the possible transcode candidates and so let FLAC audio streams be transcoded to AAC as they should.

[baranator]

Yesterday i installed jellyfin for the first time. I want jellyfin to transcode to my old thin client in the livingroom h265 and av1 material that is Full HD and to heavy for that client.

With a av1/2160p file with vorbis-audio i ran into the same Problem. Looking for the shell command that @xingoxu mentioned i noticed that in my case jellyfin serves vorbis regardless of what i set the preferred audio codec in the kodi-jellyfin-addon to. When i copied the command and ran it locally on my PC i get the following warning:

[mpegts @ 0x7affe899ab40] Stream 1, codec vorbis, is muxed as a private data stream and may not be recognized upon reading.

This happens for -codec:a:0 libvorbis and for -codec:a:0 flac too.

I found the following thread where someone states:

FFmpeg supports the following audio codecs in M2TS: BluRay PCM, AC-3, E-AC-3, DTS and TrueHD. You'll have to transcode to one of these.

In the ffmpeg code there seems to be the function, that decides which codec is compatible for muxing ts, flac is missing, libvorbis too.

So my guess is that this error at least somehow is on jellyfins side: If TS does not support that codec for muxing it should not deliver a broken transcoded file that simply ignores incompatible streams. On the other hand on the kodi-plugin side: There should be a better way to definitly set/force a preferred codec and not a set of codecs (vorbis, flac), that are known to cause the jellyfin server render unusable files.

I will have a deeper look into the kodi-addon later...