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Merged
jrusso1020 merged 1 commit into from
Apr 7, 2026
Merged

fix(engine): add bt709 color space + range conversion to encoding #223

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102 changes: 101 additions & 1 deletion packages/engine/src/services/chunkEncoder.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ describe("buildEncoderArgs anti-banding", () => {
);
const paramIdx = args.indexOf("-x264-params");
expect(paramIdx).toBeGreaterThan(-1);
expect(args[paramIdx + 1]).toBe("aq-mode=3");
expect(args[paramIdx + 1]).toContain("aq-mode=3");
expect(args[paramIdx + 1]).not.toContain("deblock");
});

Expand All @@ -132,3 +132,103 @@ describe("buildEncoderArgs anti-banding", () => {
expect(args.indexOf("-x265-params")).toBe(-1);
});
});

describe("buildEncoderArgs color space", () => {
const baseOptions = { fps: 30, width: 1920, height: 1080 };
const inputArgs = ["-framerate", "30", "-i", "frames/%04d.png"];

it("adds bt709 color space metadata for h264 CPU encoding", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h264", preset: "medium", quality: 23 },
inputArgs,
"out.mp4",
);
// FFmpeg-level metadata tags
expect(args).toContain("-colorspace:v");
expect(args[args.indexOf("-colorspace:v") + 1]).toBe("bt709");
expect(args[args.indexOf("-color_primaries:v") + 1]).toBe("bt709");
expect(args[args.indexOf("-color_trc:v") + 1]).toBe("bt709");
expect(args[args.indexOf("-color_range") + 1]).toBe("tv");
// x264-params VUI embedding
const paramIdx = args.indexOf("-x264-params");
expect(args[paramIdx + 1]).toContain("colorprim=bt709");
expect(args[paramIdx + 1]).toContain("transfer=bt709");
expect(args[paramIdx + 1]).toContain("colormatrix=bt709");
});

it("adds bt709 color space metadata for h265 CPU encoding", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h265", preset: "medium", quality: 23 },
inputArgs,
"out.mp4",
);
expect(args).toContain("-colorspace:v");
expect(args[args.indexOf("-colorspace:v") + 1]).toBe("bt709");
// x265-params VUI embedding
const paramIdx = args.indexOf("-x265-params");
expect(args[paramIdx + 1]).toContain("colorprim=bt709");
});

it("adds range conversion filter for CPU h264 encoding", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h264", preset: "medium", quality: 23 },
inputArgs,
"out.mp4",
);
const vfIdx = args.indexOf("-vf");
expect(vfIdx).toBeGreaterThan(-1);
expect(args[vfIdx + 1]).toContain("scale=in_range=pc:out_range=tv");
});

it("prepends range conversion to VAAPI filter chain", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h264", preset: "medium", quality: 23, useGpu: true },
inputArgs,
"out.mp4",
"vaapi",
);
const vfIdx = args.indexOf("-vf");
expect(vfIdx).toBeGreaterThan(-1);
expect(args[vfIdx + 1]).toBe("scale=in_range=pc:out_range=tv,format=nv12,hwupload");
});

it("skips range conversion filter for non-VAAPI GPU encoding", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h264", preset: "medium", quality: 23, useGpu: true },
inputArgs,
"out.mp4",
"nvenc",
);
expect(args.indexOf("-vf")).toBe(-1);
// but still has color metadata
expect(args).toContain("-colorspace:v");
});

it("does not add color metadata for VP9", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "vp9", preset: "good", quality: 23 },
inputArgs,
"out.webm",
);
expect(args).not.toContain("-colorspace:v");
});

it("adds video_track_timescale for h264", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "h264", preset: "medium", quality: 23 },
inputArgs,
"out.mp4",
);
expect(args).toContain("-video_track_timescale");
expect(args[args.indexOf("-video_track_timescale") + 1]).toBe("90000");
});

it("does not add timescale for VP9", () => {
const args = buildEncoderArgs(
{ ...baseOptions, codec: "vp9", preset: "good", quality: 23 },
inputArgs,
"out.webm",
);
expect(args).not.toContain("-video_track_timescale");
});
});
40 changes: 36 additions & 4 deletions packages/engine/src/services/chunkEncoder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -100,13 +100,15 @@ export function buildEncoderArgs(
if (bitrate) args.push("-b:v", bitrate);
else args.push("-crf", String(quality));

// Anti-banding: aq-mode=3 redistributes bits to dark flat areas (gradients),
// deblock smooths quantization boundaries that cause visible bands.
// Encoder-specific params: anti-banding + bt709 color space.
// aq-mode=3 redistributes bits to dark flat areas (gradients).
// colorprim/transfer/colormatrix embed bt709 in the H.264/H.265 VUI.
const xParamsFlag = codec === "h264" ? "-x264-params" : "-x265-params";
const colorParams = "colorprim=bt709:transfer=bt709:colormatrix=bt709";
if (preset === "ultrafast") {
args.push(xParamsFlag, "aq-mode=3");
args.push(xParamsFlag, `aq-mode=3:${colorParams}`);
} else {
args.push(xParamsFlag, "aq-mode=3:aq-strength=0.8:deblock=1,1");
args.push(xParamsFlag, `aq-mode=3:aq-strength=0.8:deblock=1,1:${colorParams}`);
}
}
} else if (codec === "vp9") {
Expand All @@ -122,6 +124,36 @@ export function buildEncoderArgs(
return [...args, "-y", outputPath];
}

// BT.709 color space metadata — Chrome screenshots are sRGB which maps to bt709.
// Tags the output so players interpret colors correctly across devices.
if (codec === "h264" || codec === "h265") {
args.push(
"-colorspace:v",
"bt709",
"-color_primaries:v",
"bt709",
"-color_trc:v",
"bt709",
"-color_range",
"tv",
);

// Convert full-range RGB input (Chrome screenshots) to limited/TV range for H.264.
// VAAPI already has a -vf chain for hwupload; prepend range conversion to it.
if (gpuEncoder === "vaapi") {
// Replace the existing VAAPI -vf with one that includes range conversion
const vfIdx = args.indexOf("-vf");
if (vfIdx !== -1) {
args[vfIdx + 1] = `scale=in_range=pc:out_range=tv,${args[vfIdx + 1]}`;
}
} else if (!shouldUseGpu) {
args.push("-vf", "scale=in_range=pc:out_range=tv");
}

// Fixed timescale for consistent A/V timing across platforms.
args.push("-video_track_timescale", "90000");
}

if (gpuEncoder !== "vaapi") {
args.push("-pix_fmt", pixelFormat);
}
Expand Down
38 changes: 34 additions & 4 deletions packages/engine/src/services/streamingEncoder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -169,13 +169,15 @@ function buildStreamingArgs(
if (bitrate) args.push("-b:v", bitrate);
else args.push("-crf", String(quality));

// Anti-banding: aq-mode=3 redistributes bits to dark flat areas (gradients),
// deblock smooths quantization boundaries that cause visible bands.
// Encoder-specific params: anti-banding + bt709 color space.
// aq-mode=3 redistributes bits to dark flat areas (gradients).
// colorprim/transfer/colormatrix embed bt709 in the H.264/H.265 VUI.
const xParamsFlag = codec === "h264" ? "-x264-params" : "-x265-params";
const colorParams = "colorprim=bt709:transfer=bt709:colormatrix=bt709";
if (preset === "ultrafast") {
args.push(xParamsFlag, "aq-mode=3");
args.push(xParamsFlag, `aq-mode=3:${colorParams}`);
} else {
args.push(xParamsFlag, "aq-mode=3:aq-strength=0.8:deblock=1,1");
args.push(xParamsFlag, `aq-mode=3:aq-strength=0.8:deblock=1,1:${colorParams}`);
}
}
} else if (codec === "vp9") {
Expand All @@ -191,6 +193,34 @@ function buildStreamingArgs(
return [...args, "-y", outputPath];
}

// BT.709 color space metadata — Chrome screenshots are sRGB which maps to bt709.
// Tags the output so players interpret colors correctly across devices.
if (codec === "h264" || codec === "h265") {
args.push(
"-colorspace:v",
"bt709",
"-color_primaries:v",
"bt709",
"-color_trc:v",
"bt709",
"-color_range",
"tv",
);

// Convert full-range RGB input (Chrome screenshots) to limited/TV range for H.264.
if (gpuEncoder === "vaapi") {
const vfIdx = args.indexOf("-vf");
if (vfIdx !== -1) {
args[vfIdx + 1] = `scale=in_range=pc:out_range=tv,${args[vfIdx + 1]}`;
}
} else if (!shouldUseGpu) {
args.push("-vf", "scale=in_range=pc:out_range=tv");
}

// Fixed timescale for consistent A/V timing across platforms.
args.push("-video_track_timescale", "90000");
}

if (gpuEncoder !== "vaapi") {
args.push("-pix_fmt", pixelFormat);
}
Expand Down
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