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feat(stream): enable GPU libplacebo in prod image + gate to real GPU

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Make libplacebo actually reachable in the shipped agent image, and refuse it
where it would be a regression.

Dockerfile (so a Vulkan-capable host can use the GPU tonemap path):
- install libvulkan1 (the Vulkan loader libplacebo links at runtime; ~150 KB)
- add 'graphics' to NVIDIA_DRIVER_CAPABILITIES so the nvidia container runtime
  mounts the Vulkan ICD (nvidia_icd.json + GLX libs) under --gpus all
Both are inert without a working Vulkan GPU — the functional probe gates use.

hls.go: gate libplacebo on a real HW encoder (HWAccel != none). A software-only
host with mesa would expose lavapipe (CPU Vulkan); the functional probe accepts
it but its tonemap is SLOWER than the zscale CPU chain, so libplacebo there is a
regression. No HW encoder -> stay on zscale.

Verified on the GPU dev box: nvenc session still picks libplacebo (-c:v
h264_nvenc -vf ...,libplacebo=...:tonemapping=bt.2390); new unit test locks the
software-encoder path onto zscale.
This commit is contained in:
Deivid Soto 2026-06-03 10:42:16 +02:00
parent cfaedb7f3b
commit 5e5a719f27
3 changed files with 47 additions and 9 deletions
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9
internal/engine/hls.go
View file

@ -1359,7 +1359,14 @@ func buildHLSFFmpegArgsAt(cfg HLSSessionConfig, probe *StreamProbe, tmpDir strin
// CPU chain; else play untonemapped (desaturated, last resort). Skip
// libplacebo on VAAPI: its Vulkan surface flow doesn't compose with our
// nv12+hwupload path, so VAAPI keeps the zscale-or-none behaviour.
useLibplacebo := probe.HDR != "" && cfg.Transcode.HasLibplacebo && codec != "h264_vaapi"
//
// Gate on a real HW encoder (HWAccel != none): only then is the Vulkan
// device a genuine GPU. A software-only host with mesa would expose lavapipe
// (CPU Vulkan), which the functional probe accepts but whose tonemap is
// SLOWER than the zscale CPU chain — so on those hosts libplacebo would be a
// regression. No HW encoder ⇒ stay on zscale.
useLibplacebo := probe.HDR != "" && cfg.Transcode.HasLibplacebo &&
codec != "h264_vaapi" && cfg.Transcode.HWAccel != HWAccelNone
tonemap := ""
if probe.HDR != "" && cfg.Transcode.TonemapHDR && !useLibplacebo {
tonemap = hdrTonemapChain

28
internal/engine/tonemap_test.go
View file

@ -68,13 +68,15 @@ func TestTonemap_AppliedInNoDownscaleBranch(t *testing.T) {
}
func TestTonemap_LibplaceboPreferredOverZscale(t *testing.T) {
// HDR source + an ffmpeg with libplacebo → the single GPU filter replaces
// the whole CPU zscale chain (and the trailing format=/setparams it folds in).
// HDR source + an ffmpeg with libplacebo on a REAL HW encoder (NVENC) → the
// single GPU filter replaces the whole CPU zscale chain (and the trailing
// format=/setparams it folds in). NVENC (not None) because libplacebo is
// gated on a real GPU — a software encoder stays on zscale.
cfg := HLSSessionConfig{
SessionID: "test",
SourcePath: "/movies/x.mkv",
Quality: "720p",
Transcode: TranscodeRuntime{FFmpegPath: "/usr/bin/ffmpeg", HWAccel: HWAccelNone, TonemapHDR: true, HasLibplacebo: true},
Transcode: TranscodeRuntime{FFmpegPath: "/usr/bin/ffmpeg", HWAccel: HWAccelNVENC, TonemapHDR: true, HasLibplacebo: true},
}
probe := &StreamProbe{Width: 3840, Height: 2160, BitDepth: 10, HDR: "HDR10", DurationSec: 100}
vf := vfChain(strings.Join(buildHLSFFmpegArgsAt(cfg, probe, "/tmp/t", 0, 0), " "))
@ -86,6 +88,26 @@ func TestTonemap_LibplaceboPreferredOverZscale(t *testing.T) {
}
}
func TestTonemap_LibplaceboSkippedOnSoftwareEncoder(t *testing.T) {
// libplacebo present but no HW encoder (software libx264) → must NOT use
// libplacebo: a software host's only Vulkan would be lavapipe (CPU), slower
// than zscale. Falls back to the zscale chain.
cfg := HLSSessionConfig{
SessionID: "test",
SourcePath: "/movies/x.mkv",
Quality: "720p",
Transcode: TranscodeRuntime{FFmpegPath: "/usr/bin/ffmpeg", HWAccel: HWAccelNone, TonemapHDR: true, HasLibplacebo: true},
}
probe := &StreamProbe{Width: 3840, Height: 2160, BitDepth: 10, HDR: "HDR10", DurationSec: 100}
vf := vfChain(strings.Join(buildHLSFFmpegArgsAt(cfg, probe, "/tmp/t", 0, 0), " "))
if strings.Contains(vf, "libplacebo") {
t.Errorf("software encoder must not use libplacebo (lavapipe trap), got %q", vf)
}
if !strings.Contains(vf, "zscale=t=linear") {
t.Errorf("software encoder with HDR + zscale should fall back to the zscale chain, got %q", vf)
}
}
func TestTonemap_SkippedWhenFFmpegLacksZscale(t *testing.T) {
vf := vfChain(hlsArgsFor("HDR10", false, HWAccelNone))
if strings.Contains(vf, "zscale") || strings.Contains(vf, "tonemap") {