Better sniffing of MPEG4 content by checking for a compatible sub-brand. (261eb0cb) · Commits · e / os / android_frameworks_base

media/libstagefright/MPEG4Extractor.cpp

+79 −1

Original line number	Diff line number	Diff line
		@@ -1633,7 +1633,7 @@ status_t MPEG4Source::read(
		}
		}

		bool SniffMPEG4(
		static bool LegacySniffMPEG4(
		const sp<DataSource> &source, String8 mimeType, float confidence) {
		uint8_t header[8];

		@@ -1657,5 +1657,83 @@ bool SniffMPEG4(
		return false;
		}

		static bool isCompatibleBrand(uint32_t fourcc) {
		static const uint32_t kCompatibleBrands[] = {
		FOURCC('i', 's', 'o', 'm'),
		FOURCC('i', 's', 'o', '2'),
		FOURCC('a', 'v', 'c', '1'),
		FOURCC('3', 'g', 'p', '4'),
		FOURCC('m', 'p', '4', '1'),
		FOURCC('m', 'p', '4', '2'),
		};

		for (size_t i = 0;
		i < sizeof(kCompatibleBrands) / sizeof(kCompatibleBrands[0]);
		++i) {
		if (kCompatibleBrands[i] == fourcc) {
		return true;
		}
		}

		return false;
		}

		// Attempt to actually parse the 'ftyp' atom and determine if a suitable
		// compatible brand is present.
		static bool BetterSniffMPEG4(
		const sp<DataSource> &source, String8 mimeType, float confidence) {
		uint8_t header[12];
		if (source->readAt(0, header, 12) != 12
		\|\| memcmp("ftyp", &header[4], 4)) {
		return false;
		}

		size_t atomSize = U32_AT(&header[0]);
		if (atomSize < 16 \|\| (atomSize % 4) != 0) {
		return false;
		}

		bool success = false;
		if (isCompatibleBrand(U32_AT(&header[8]))) {
		success = true;
		} else {
		size_t numCompatibleBrands = (atomSize - 16) / 4;
		for (size_t i = 0; i < numCompatibleBrands; ++i) {
		uint8_t tmp[4];
		if (source->readAt(16 + i * 4, tmp, 4) != 4) {
		return false;
		}

		if (isCompatibleBrand(U32_AT(&tmp[0]))) {
		success = true;
		break;
		}
		}
		}

		if (!success) {
		return false;
		}

		*mimeType = MEDIA_MIMETYPE_CONTAINER_MPEG4;
		*confidence = 0.3f;

		return true;
		}

		bool SniffMPEG4(
		const sp<DataSource> &source, String8 mimeType, float confidence) {
		if (BetterSniffMPEG4(source, mimeType, confidence)) {
		return true;
		}

		if (LegacySniffMPEG4(source, mimeType, confidence)) {
		LOGW("Identified supported mpeg4 through LegacySniffMPEG4.");
		return true;
		}

		return false;
		}

		} // namespace android