The presence of a FLAC stream seems to change Plex's interpretation of the MKV's bitrate

General Discussions
1

I have two video files in comparison. Both with similar video bitrates of around 7700 kpbs. One has a 640 kpbs AC-3 audio file, and the other has a FLAC audio file 3000 kpbs.

For the AC-3 file, Plex will direct stream video and audio when the player is set to 8mbps or higher, even though the total bitrate of the stream would be over 8,000.

For the FLAC file, it will always transcode the audio to the player (as expected), but it will begin to transcode the video if the player’s setting is below 12mbps, even though I know the transcoded AC-3 audio is probably the same, or less, than the AC-3 file mentioned above.

Looking at the XML data of the file in Plex it looks like the total bitrate is interpreted as the marker for when video should be transcoded for the player, while the AC-3 file’s XML is split among audio and video streams.

The video of the file with FLAC audio is being punished even though it’s sending out transcoded audio similar to the first file. Is this correct?

2

The bitrate setting should only look at the video stream. Your file with the flac audio should not be transcoding the video. Can you set the quality to 8 playback then provide me the server log?

3

Ah. Never mind. I just looked at the xml and I see what you are talking about. The entire bitrate is assigned to the video portion. So PMS is handling the transcoding properly, but it may be failing in the analysis so PMS if being given bad information. Let me look into this and I’ll get back to you.

4

Any update on this?

Not sure if this is related, but I’ve recently realized sometimes MediaInfo will not show any bitrate info for any of the separate streams if I have a DTS-HD file embedded in the MKV. This seems to happen when you pass it through with Handbrake, but if you mux your own file using MKVToolnix using the extracted DTS-HD track from the original file, it will show all the normal details.

I just had an issue with a file where MediaInfo would not show bitrate. I re-muxed it and now it’s correct, yet when I view it in Plex, it only sees the total bitrate for the file and shows no bitrate for the streams. This is a DTS-HD track, not FLAC.

5

The devs are investigating. It appears to be a combination of the files not reporting properly and PMS not detecting it correctly in certain instances. I don’t have any news when a fix will be available.