Server Version: 1.41.2.9239-0b158cae0 (HEVC Preview)
Currently I have an AV1 file with a average bitrate of 2.9 Mbps, however when playing the file on a device that does not support AV1 decode and thus forces transcoding. However, the bitrate that the file is being transcoded/streamed as is averaging something like 30 Mbps. All of this is to say that if a file is being transcoded a setting to limit the max transcode bitrate or to not exceed the original files average bitrate would be extremely useful as I would still want to allow direct streams for higher bitrate files but to make sure that transcoded files do not have some insane bitrate bloat.
Currently player setting are set to use original quality while streaming…
Also please note that while I am using the HEVC preview I noticed the same transcode bloat when turning the option to use HEVC to off so it apparently exists on AVC transcoding as well.
That doesn’t make sense.
If the source codec is more efficient, it needs less bitrate to transport a certain visual quality. The target codec can be less efficient and thus needs more bitrate in order not to degrade the quality, despite the transcoding.
On top of that, with HEVC as target codec, Plex uses hardware transcoding, which is less efficient and also of lesser visual quality at a given bitrate than a pure software encode. Thus, in order to preserve quality, it makes sense to use a higher target bitrate. Which one that is, can be defined
- in the settings of the client, often separately for local and remote connections
- in the settings of the server for remote connections specifically
Original Quality is not original bitrate. Each transcoding is lowering the overall quality. In order to preserve the quality despite the transcoding, one should use a higher target bitrate.
@OttoKerner
I’m getting this too:
1.5Mbps AV1 > 21Mbps
6.7Mbps AV1 > 81.6Mbps
This feature request is actually a campaign to correct a bug. I think there is a decimal in the wrong place. Everywhere this is being brought up on the Plex forum it is explained away with reasons that it might be intentional. It is certainly a long standing AV1 transcoding decision bug.
Please pause to consider if you think transcoding to 82Mbps is a Plex developer choice and not a bug.
Please get this in front of the devs ASAP. We need to be able to use AV1 libraries and this bug has been a showstopper since it was implemented.
More info to verify that this is a nasty bug:
https://support.plex.tv/articles/115002178853-using-hardware-accelerated-streaming/
”(a good rule of thumb is it will generate the same resolution as a h.264 transcode at 1.5x the bitrate)”
It’s doing about 15x with Arc hardware transcoding. This is a 100% confirmed to be decimal bug or possibly they mixed up kbps with mbps. In the past year or two any mention of this here and on Plex has been shut down by posters claiming it is intended, but the official Plex documentation tells the truth here.
Please get this to the devs, it has gone on far too long. Hardware transcoding on an Arc card is not a fringe case, I got the darn thing just for Plex.
@OttoKerner Really sorry to nag but I have been getting crickets for years over this now.
I agree with you that a transcode to a higher bitrate is reasonable and the Plex documentation backs you up too. But OP’s example of 2.9Mbps to “something like 30 Mbps” is over 10x. My own experience is transcoding 12x to 15x the size of the source. The documentation from Plex references 1.5x for h264 transcodes. I realize AV1 is more efficient than AVC but 10x to 15x is obviously a bug.
I would really appreciate getting this in front of a decision maker.
