AMD HW AV1 exceeds configured bitrate in CBR
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 35/100
- Issue type
- Bug
- Clarity
- Needs clarification
- Activity status
- Stale
- Tech stack
- c
- Domain
- audio-video-rtc
Research direction
Start by reviewing the supplied OBS Studio log and reproducing the issue with AMD HW AV1, CBR at 40000 Kbps, a 2-second keyframe interval, and three B-frames. Compare the status-bar bitrate with the configured limit and the H.265 or zero-B-frame workarounds; done means CBR no longer regularly exceeds the configured bitrate.
Written by the indexing model from the issue text.
Description
Operating System Info
Windows 11
OBS Studio Version
31.0.2
OBS Studio Log URL
https://obsproject.com/logs/izBJ78bgmybogosH
Expected Behavior
Bitrate should never exceed configured bitrate when using constant bitrate control with b-frames.
Current Behavior
Bitrate is unstable and regularly exceeds configured bitrate.
Steps to Reproduce
- Video Encoder AMD HW AV1
- Rate Control CBR
- Bitrate 40000 Kbps
- Keyframe Interval 2s
- Max B-frames 3
- Start stream
- Observe bitrate exceeds 40000 Kbps in status bar
Anything else we should know?
I noticed this issue when my YouTube stream started to drop frames, even though obs never dropped any frames. This is likely caused by b-frames spiking bitrate to be over 55 Mbps, which is the maximum YouTube will receive. YouTube then drops frames.
My workaround is to use AMD HW H.265 (HEVC) or setting Max B-frames to zero.
- Dominant language
- C
- Stars
- 76.4k
- Forks
- 10.2k
- Avg merge
- 4d 23h
- Merged PRs (30d)
- 12
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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