Skip scaling_list definitions in AVC seq header. (6dc91c95) · Commits · e / os / android_frameworks_av

media/libstagefright/avc_utils.cpp

+37 −1

Original line number	Diff line number	Diff line
		@@ -40,6 +40,25 @@ unsigned parseUE(ABitReader *br) {
		return x + (1u << numZeroes) - 1;
		}

		signed parseSE(ABitReader *br) {
		unsigned codeNum = parseUE(br);

		return (codeNum & 1) ? (codeNum + 1) / 2 : -(codeNum / 2);
		}

		static void skipScalingList(ABitReader *br, size_t sizeOfScalingList) {
		size_t lastScale = 8;
		size_t nextScale = 8;
		for (size_t j = 0; j < sizeOfScalingList; ++j) {
		if (nextScale != 0) {
		signed delta_scale = parseSE(br);
		nextScale = (lastScale + delta_scale + 256) % 256;
		}

		lastScale = (nextScale == 0) ? lastScale : nextScale;
		}
		}

		// Determine video dimensions from the sequence parameterset.
		void FindAVCDimensions(
		const sp<ABuffer> &seqParamSet,
		@@ -63,7 +82,24 @@ void FindAVCDimensions(
		parseUE(&br); // bit_depth_luma_minus8
		parseUE(&br); // bit_depth_chroma_minus8
		br.skipBits(1); // qpprime_y_zero_transform_bypass_flag
		CHECK_EQ(br.getBits(1), 0u); // seq_scaling_matrix_present_flag

		if (br.getBits(1)) { // seq_scaling_matrix_present_flag
		for (size_t i = 0; i < 8; ++i) {
		if (br.getBits(1)) { // seq_scaling_list_present_flag[i]

		// WARNING: the code below has not ever been exercised...
		// need a real-world example.

		if (i < 6) {
		// ScalingList4x4[i],16,...
		skipScalingList(&br, 16);
		} else {
		// ScalingList8x8[i-6],64,...
		skipScalingList(&br, 64);
		}
		}
		}
		}
		}

		parseUE(&br); // log2_max_frame_num_minus4