From 6b2a1ec1325e5f1bd9629f6a9f9a2de560fde047 Mon Sep 17 00:00:00 2001
From: Aditya Garud <153842990+yashranaway@users.noreply.github.com>
Date: Sun, 1 Nov 2026 08:01:11 +0000
Subject: [PATCH] fix(media-server): re-encode H.264 uploads that are not 8-bit
 4:2:0

---
 .../lib/media-video.integration.test.ts       | 67 +++++++++++++++++++
 apps/media-server/src/lib/media-video.ts      | 31 +++++++--
 2 files changed, 94 insertions(+), 4 deletions(-)

diff --git a/apps/media-server/src/__tests__/lib/media-video.integration.test.ts b/apps/media-server/src/__tests__/lib/media-video.integration.test.ts
index e3b8d3e7f73..e40fa56a2bf 100644
--- a/apps/media-server/src/__tests__/lib/media-video.integration.test.ts
+++ b/apps/media-server/src/__tests__/lib/media-video.integration.test.ts
@@ -70,6 +70,23 @@ function readH264Level(filePath: string): number {
 	return Number.parseInt(output, 10);
 }
 
+function readVideoPixelFormat(filePath: string): string {
+	return execFileSync("ffprobe", [
+		"-hide_banner",
+		"-v",
+		"error",
+		"-select_streams",
+		"v:0",
+		"-show_entries",
+		"stream=pix_fmt",
+		"-of",
+		"default=noprint_wrappers=1:nokey=1",
+		filePath,
+	])
+		.toString()
+		.trim();
+}
+
 function readDecodedStreamHash(filePath: string, stream: "v" | "a") {
 	return execFileSync("ffmpeg", [
 		"-hide_banner",
@@ -1314,6 +1331,56 @@ describe("processVideo integration tests", () => {
 		}
 	}, 120000);
 
+	test("re-encodes h264 input that is not 8-bit 4:2:0", async () => {
+		const workDir = mkdtempSync(join(tmpdir(), "cap-h264-pixel-format-"));
+		try {
+			for (const source of [
+				{ pixelFormat: "yuv444p", level: "3.0" },
+				{ pixelFormat: "yuv420p10le", level: "3.0" },
+				{ pixelFormat: "yuv444p", level: "6.2" },
+			]) {
+				const sourcePath = join(
+					workDir,
+					`${source.pixelFormat}-${source.level}.mp4`,
+				);
+				execFileSync("ffmpeg", [
+					"-hide_banner",
+					"-loglevel",
+					"error",
+					"-y",
+					"-i",
+					TEST_VIDEO_WITH_AUDIO,
+					"-c:v",
+					"libx264",
+					"-pix_fmt",
+					source.pixelFormat,
+					"-level:v",
+					source.level,
+					"-c:a",
+					"copy",
+					sourcePath,
+				]);
+				const metadata = await probeVideo(`file://${sourcePath}`);
+
+				const tempFile = await processVideo(sourcePath, metadata, {
+					maxWidth: metadata.width,
+					maxHeight: metadata.height,
+					normalizeH264Level: true,
+				});
+				tempFiles.push(tempFile.path);
+
+				expect(readVideoPixelFormat(tempFile.path)).toBe("yuv420p");
+				const outputMetadata = await probeVideo(`file://${tempFile.path}`);
+				expect(outputMetadata.videoCodec).toBe("h264");
+				expect(outputMetadata.audioCodec).toBe("aac");
+
+				await tempFile.cleanup();
+			}
+		} finally {
+			rmSync(workDir, { recursive: true, force: true });
+		}
+	}, 120000);
+
 	test("transcodes raw webm input into a valid mp4 output", async () => {
 		const workDir = mkdtempSync(join(tmpdir(), "cap-webm-transcode-"));
 		try {
diff --git a/apps/media-server/src/lib/media-video.ts b/apps/media-server/src/lib/media-video.ts
index 1baf6817d9a..68498a51710 100644
--- a/apps/media-server/src/lib/media-video.ts
+++ b/apps/media-server/src/lib/media-video.ts
@@ -1577,6 +1577,21 @@ async function probeH264Level(
 	return Number.isFinite(level) && level > 0 ? level : null;
 }
 
+// Safari, phones and Firefox on Windows play H.264 through hardware decoders that only take 8-bit 4:2:0.
+const BROWSER_H264_PIXEL_FORMATS = new Set(["yuv420p", "yuvj420p"]);
+
+async function probeH264PixelFormat(
+	inputPath: string,
+	abortSignal?: AbortSignal,
+): Promise<string | null> {
+	const stdout = await probeVideoStreamEntries(
+		inputPath,
+		"stream=pix_fmt",
+		abortSignal,
+	);
+	return stdout?.split(/\s+/)[0] || null;
+}
+
 async function probeVideoRotation(
 	inputPath: string,
 	abortSignal?: AbortSignal,
@@ -1609,22 +1624,30 @@ export async function processVideo(
 	const outputTempFile = await createTempFile(".mp4");
 
 	const remuxOnly = opts.remuxOnly;
-	const sourceH264Level =
+	const [sourceH264Level, sourcePixelFormat] =
 		!remuxOnly && metadata.videoCodec === "h264"
-			? await probeH264Level(inputPath, abortSignal)
-			: null;
+			? await Promise.all([
+					probeH264Level(inputPath, abortSignal),
+					probeH264PixelFormat(inputPath, abortSignal),
+				])
+			: [null, null];
 	abortSignal?.throwIfAborted();
+	const browserPixelFormat =
+		sourcePixelFormat === null ||
+		BROWSER_H264_PIXEL_FORMATS.has(sourcePixelFormat);
 	const targetH264Level = pickMobileSafeH264Level(metadata, opts);
 	const normalizeH264Level =
 		opts.normalizeH264Level &&
 		metadata.videoCodec === "h264" &&
+		browserPixelFormat &&
 		sourceH264Level !== null &&
 		sourceH264Level > targetH264Level.value &&
 		metadata.width <= opts.maxWidth &&
 		metadata.height <= opts.maxHeight;
 	const videoTranscode = remuxOnly
 		? false
-		: needsVideoTranscode(metadata, opts, sourceH264Level);
+		: !browserPixelFormat ||
+			needsVideoTranscode(metadata, opts, sourceH264Level);
 	const audioTranscode = remuxOnly ? false : needsAudioTranscode(metadata);
 	const extraInputArgs = resilientFlags
 		? buildExtraInputFlags(resilientFlags)