Quality transcoding presets don't match reality

[blockdor 0]

Hey

So when I transcode a 4k hdr film using 1080p 12Mbit/s the resulting file has a bitrate of 2.5-5Mbit/s (I used a reference 60fps video to achieve the 5mb, 2.5mb was from a standard 24fps movie)

Are the presets editable in Emby as the indicated bitrates (and resolutions) are completely wrong for my setup.

Attached is a log of the reference clip transcode at crf 18 at veryslow and veryfast.

Even at 60fps (which is not usual for general broadcast) it's still half what it should be.

Cheers

Alex

 

 

ffmpeg-transcode-f31d9734-a6e8-4a30-ba81-1388341b4689_1.txt ffmpeg-transcode-016f2aa3-ab27-4a55-bc04-d41e331d029d_1.txt

[blockdor 0]

So for example I could change that 10mbit preset to 2.5mbit and then the maxrate ffmpeg setting might actually get used instead of the whole bitrate being crf controlled.

Edited December 15, 2023 by blockdor

[Luke 42081]

HI there, what is the quality setting configured to?

[blockdor 0]

I tried it at veryslow and veryfast to just check it wasn't that causing the issue.

A

[blockdor 0]

The 10mbit 1080p present is what indicated to me that the bitrates weren't quite correct.

Maybe an improvement in ffmpeg efficiency x264 since they were first decided?

Annoyingly if i wanted say 5 mbit 1080p i can't do it since the resolutions are reduced for the lower bandwitch. (5mbit is 720x404 i think), only at the 10mbit preset or thereabouts does the resolution actually become 1080p.

I'd like to be a bit more generous with the resolutions at lower bandwidths or at least set the res to what it specified in the preset.

TLDR I'd like to have a 1080p present at 2 and 3mbit that is actually 1080p to the client.

A

Edited December 17, 2023 by blockdor

[Luke 42081]

Hi @blockdorare you able to try the 4.8 beta server and see how that compares? There's a lot of transcoding related changes so it's probably best to reevaluate on that. Thanks.