Linux/Wayland: capture frame rate drops 60 -> ~29 fps with OpenH264 encoder errors

[EtienneLescot]

Reported on v1.7.0-rc.1, Linux Wayland, Intel iGPU.

Symptoms

• Recording runs at ~29 fps instead of 60, regardless of source.
• OpenH264 encoder errors in the logs.
• Reporter tried forcing VP8 everywhere instead of H.264; no improvement.

Hypothesis

Likely downstream of #91 (Vulkan/DMA-BUF import failure). When the zero-copy DMA-BUF import fails, the PipeWire stream renegotiates to a software/linear buffer path. That software copy + software H.264 (Chromium bundles OpenH264 for MediaRecorder on Linux; no VAAPI path there) can't sustain 60 fps, so throughput halves and the encoder is stressed. The VP8 swap not helping is consistent with the bottleneck being frame delivery, not the codec.

Next steps

1. Re-test fps on the fix(recording): disable Vulkan on Wayland so PipeWire capture can import DMA-BUF frames #91 build (Vulkan disabled) first. This may resolve or improve it.
2. If still capped, this is a genuine encoder-throughput issue. Attach the exact OpenH264 error lines and the MediaRecorder config (codec/bitrate/fps) used for capture.

Env

Compositor, Mesa version, Intel GPU.

[EtienneLescot]

Reporter validated the #91 build on Wayland + Intel: 60 fps in and out, issue no longer reproduces. Confirms this was downstream of the DMA-BUF import failure (#92) falling back to a software buffer path, not an OpenH264/codec bug. Will close when #91 merges.

[github-actions]

Fixed by #91 and merged into main.

This change is assigned to the Next Release release milestone and is not necessarily available in the latest downloadable desktop release yet. It is currently marked as status: pending release until a packaged release containing it is published.

[EtienneLescot]

Moved into v1.7.0 as part of the pre-release cut.