Recording (Windows): encode H.264 with the High profile

[EtienneLescot]

Part of #920 (rank 3). Effort S, risk low.

Problem

• Screen and webcam are encoded as H.264 Constrained Baseline, 1 reference frame, CAVLC (measured with ffprobe). mf_encoder.cpp never sets MF_MT_MPEG2_PROFILE, so the Media Foundation encoder picks Baseline.
• Re-encoding the same recordings through the same hardware MFT (NVENC, h264_mf -hw_encoding 1) at equal bitrate:
  • screen: +1.7 dB PSNR (45.31 → 46.98 dB at 4 Mbit/s);
  • webcam: +1.9 VMAF (89.11 → 91.05 at 4 Mbit/s).

Proposal

• Ask for eAVEncH264VProfile_High on the output type (and CODECAPI_AVEncMPVProfile where the MFT reads it), with a fallback to the current behaviour if the encoder refuses it.
• No B-frames: they broke the fragmented writer on macOS (negative offsets). Keep the GOP as is.

Verify

• ffprobe reads profile=High on both tracks, hardware and software encoder paths.
• Fragmented MP4 still plays and seeks; the compositor decodes and exports it.

[github-actions]

Fixed by #929 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 v2.0.0 as part of the pre-release cut.