Proper chunk size computation for Layer II/III V2 and V2.5, skip optional ID3 tag. (63f20ec1) · Commits · e / os / android_frameworks_base

media/libstagefright/MP3Extractor.cpp

+33 −1

Original line number	Diff line number	Diff line
		@@ -147,7 +147,12 @@ static bool get_mp3_frame_size(
		*out_bitrate = bitrate;
		}

		if (version == 3 /* V1 */) {
		frame_size = 144000 bitrate / sampling_rate + padding;
		} else {
		// V2 or V2.5
		frame_size = 72000 bitrate / sampling_rate + padding;
		}
		}

		if (out_sampling_rate) {
		@@ -166,6 +171,33 @@ static bool get_mp3_frame_size(
		static bool Resync(
		const sp<DataSource> &source, uint32_t match_header,
		off_t inout_pos, uint32_t out_header) {
		if (*inout_pos == 0) {
		// Skip an optional ID3 header if syncing at the very beginning
		// of the datasource.

		uint8_t id3header[10];
		if (source->read_at(0, id3header, sizeof(id3header))
		< (ssize_t)sizeof(id3header)) {
		// If we can't even read these 10 bytes, we might as well bail out,
		// even if there _were_ 10 bytes of valid mp3 audio data...
		return false;
		}

		if (id3header[0] == 'I' && id3header[1] == 'D' && id3header[2] == '3') {
		// Skip the ID3v2 header.

		size_t len =
		((id3header[6] & 0x7f) << 21)
		\| ((id3header[7] & 0x7f) << 14)
		\| ((id3header[8] & 0x7f) << 7)
		\| (id3header[9] & 0x7f);

		len += 10;

		*inout_pos += len;
		}
		}

		// Everything must match except for
		// protection, bitrate, padding, private bits and mode extension.
		const uint32_t kMask = 0xfffe0ccf;