feat: use vpp_qsv hardware padding when available - #182
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QSV padding currently falls back to the software pad filter, which forces an hwdownload/hwupload round-trip per frame. Measured on an Intel Arc Pro B50 (640x480 4:3 -> 1440x1080 padded to 1920x1080, h264), that chain runs at 212 fps / 5.2s CPU versus 563 fps / 1.3s CPU for a hardware pad — parity with pad_vaapi, and essentially free relative to plain scaling. ffmpeg's vpp_qsv only gained pad_w/pad_h/pad_x/pad_y/pad_color in patched builds (submission to ffmpeg-devel pending), so plain filter presence cannot gate this. FfmpegInfo now probes AVOptions for selected filters via `ffmpeg -h filter=NAME` (currently just vpp_qsv), and the QSV best_filter substitutes PadQsv only when the pad_w option is advertised; otherwise behaviour is unchanged and the software pad chain is used. Co-Authored-By: Claude Fable 5 <[email protected]>
Chaining two vpp_qsv instances (scale then pad) drops the final frame at EOF on real hardware (measured on Intel B50: 1439/1440 packets). This reproduces with two plain vpp_qsv scales on stock ffmpeg, so it is a pre-existing ffmpeg flush quirk we must avoid triggering. A single combined instance delivers every frame and uses one VPP session. PadQsv gains an optional fused ScaleQsv; the optimize() pass folds a ScaleQsv into an immediately-following PadQsv (mirroring the existing CUDA fusion), emitting one vpp_qsv=w=..:h=..:pad_w=..:pad_h=..:pad_x=-1:pad_y=-1:pad_color=black. Pad-only chains, scale-only chains, and the software fallback are unchanged. The pad_w capability gate still governs the combined form. Co-Authored-By: Claude Fable 5 <[email protected]>
This was referenced Jul 30, 2026
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Two commits:
feat: use vpp_qsv hardware padding when available —
FfmpegInfogains per-filter option probing (
ffmpeg -h filter=vpp_qsv), and theQSV
best_filtersubstitutes a hardwarePadQsvop for the softwarepad when the binary's
vpp_qsvhaspad_w. On stock ffmpeg the probefinds nothing and the existing software pad chain is emitted unchanged
— no behavior change without a patched binary (see companion
ErsatzTV-ffmpeg PR; the patches are also on ffmpeg-devel upstream).
perf: fuse qsv scale+pad into a single vpp_qsv instance — measured
on hardware: two chained
vpp_qsvinstances drop the final frame atEOF (1439/1440; reproducible with two plain scales on stock ffmpeg), a
single combined instance does not. The fusion pass follows the existing
CUDA scale/format fusion precedent in
FilterChain::optimize().Emitted chain for the canonical 4:3→16:9 case:
Validated end-to-end with the real
ersatztv-channelworker on anIntel Arc Pro B50: patched-ffmpeg arm emits the fused chain with no
hwdownload and produces true-black 1920x1080 HLS segments
(Y/U/V = 16/128/128); stock-ffmpeg arm falls back to the software pad
and works. Benchmarks: GPU pad at parity with pad_vaapi (563 fps) vs
212 fps for the hwdownload/pad/hwupload chain. Running in production
against live channels since 2026-07-30.
Known limitation (pre-existing, unchanged): anamorphic sources use a
separate SAR pre-scale instance ahead of the fused scale+pad, so they
still emit two chained instances and keep the pre-existing EOF
last-frame behavior.
Companion PRs: ErsatzTV/ErsatzTV-ffmpeg#42 (carries the ffmpeg patches),
ErsatzTV/legacy#2965 (same feature for the C# pipeline).