forked from marfrit/marfrit-packages
marfrit
5c69460722
FFmpeg 8.x dropped the H.264 decoder's low_delay code path — AV_CODEC_FLAG_LOW_DELAY no longer prevents h264_select_output_frame from running the display-order DPB output queue. The daedalus-v4l2 daemon's `ctx->flags |= AV_CODEC_FLAG_LOW_DELAY` at daemon/src/decoder.c:202 has been a silent no-op since the SONAME 61→62 jump landed in reauktion/daedalus-v4l2 PR #16; on Firefox YouTube this re-introduced the 2-1-4-3 B-frame pair-swap that PR #12's daemon flag was supposed to prevent. Fix lives in libavcodec, not the daemon: restore the documented LOW_DELAY semantics so the daemon (and any other V4L2-stateless- style consumer) keeps the one-frame-per-send_packet decode-order output contract it already declares. ## Patch 0006-h264-restore-low-delay.patch touches libavcodec/h264_slice.c: - h264_select_output_frame: early-exit when LOW_DELAY is set. Emit the just-decoded picture as next_output_pic, mirror the corruption / recovery-point tracking the main path performs, skip delayed_pic[] / POC reorder machinery entirely. - h264_field_start: suppress the SPS-driven `has_b_frames = sps->num_reorder_frames` clobber when LOW_DELAY is set. Without this the per-slice bitstream_restriction_flag re-pickup would reintroduce a nonzero reorder buffer mid-stream even after the daemon set has_b_frames=0 at avcodec_open2. ## Why not daemon-side A daemon SPS-rewrite (`num_reorder_frames=0`) was considered but rejected: it works only for the daemon's reconstructed SPS NAL, not for any in-band SPS the daemon dlopens libavformat to parse in other code paths. Restoring documented FFmpeg flag semantics is the smaller, more durable change and keeps the daemon interface stable. ## Packaging - PKGREL/pkgrel bump to 9. - No new build-deps, no Depends change. - Substitution arc cycles 6/7/8 unchanged. ## Refs - reauktion/daedalus-v4l2#11 / #12 (LOW_DELAY half-measure on daemon side, originally landed against FFmpeg 7.x). - daemon/src/decoder.c:202 (`ctx->flags |= AV_CODEC_FLAG_LOW_DELAY` for H.264 only — unchanged, but now actually has effect again).