- Metadata is usefule in carrying extra information that correlated with video or audio to - facilate offline processing, e.g. gyro signals from the sensor. Meatadata track is only - supported in MP4 format. When adding a metadata track, track's mime format must start with - prefix "application/", e.g. "applicaton/gyro". Metadata's format/layout will be defined by - the application. The generated MP4 file uses TextMetaDataSampleEntry defined in section 12.3.3.2 - of the ISOBMFF to signal the metadata's mime format. When using {@link android.media.MediaExtractor} - to extract the file with metadata track, the mime format of the metadata will be extracted into - {@link android.media.MediaFormat}. + Per-frame metadata is useful in carrying extra information that correlated with video or audio to + facilitate offline processing, e.g. gyro signals from the sensor could help video stabilization when + doing offline processing. Metaadata track is only supported in MP4 container. When adding a new + metadata track, track's mime format must start with prefix "application/", e.g. "applicaton/gyro". + Metadata's format/layout will be defined by the application. Writing metadata is nearly the same as + writing video/audio data except that the data will not be from mediacodec. Application just needs + to pass the bytebuffer that contains the metadata and also the associated timestamp to the + {@link #writeSampleData} api. The timestamp must be in the same time base as video and audio. The + generated MP4 file uses TextMetaDataSampleEntry defined in section 12.3.3.2 of the ISOBMFF to signal + the metadata's mime format. When using{@link android.media.MediaExtractor} to extract the file with + metadata track, the mime format of the metadata will be extracted into {@link android.media.MediaFormat}.
MediaMuxer muxer = new MediaMuxer("temp.mp4", OutputFormat.MUXER_OUTPUT_MPEG_4);
- // More often, the MediaFormat will be retrieved from MediaCodec.getOutputFormat()
- // or MediaExtractor.getTrackFormat().
+ // SetUp Video/Audio Tracks.
MediaFormat audioFormat = new MediaFormat(...);
MediaFormat videoFormat = new MediaFormat(...);
+ int audioTrackIndex = muxer.addTrack(audioFormat);
+ int videoTrackIndex = muxer.addTrack(videoFormat);
// Setup Metadata Track
MediaFormat metadataFormat = new MediaFormat(...);
metadataFormat.setString(KEY_MIME, "application/gyro");
-
- int audioTrackIndex = muxer.addTrack(audioFormat);
- int videoTrackIndex = muxer.addTrack(videoFormat);
int metadataTrackIndex = muxer.addTrack(metadataFormat);
- ByteBuffer inputBuffer = ByteBuffer.allocate(bufferSize);
- boolean finished = false;
- BufferInfo bufferInfo = new BufferInfo();
muxer.start();
- while(!finished) {
- // getInputBuffer() will fill the inputBuffer with one frame of encoded
- // sample from either MediaCodec or MediaExtractor, set isAudioSample to
- // true when the sample is audio data, set up all the fields of bufferInfo,
- // and return true if there are no more samples.
- finished = getInputBuffer(inputBuffer, sampleType, bufferInfo);
- if (!finished) {
- int currentTrackIndex = getTrackIndex(sampleType);
- muxer.writeSampleData(currentTrackIndex, inputBuffer, bufferInfo);
- }
+ while(..) {
+ // Allocate bytebuffer and write gyro data(x,y,z) into it.
+ ByteBuffer metaData = ByteBuffer.allocate(bufferSize);
+ metaData.putFloat(x);
+ metaData.putFloat(y);
+ metaData.putFloat(z);
+ BufferInfo metaInfo = new BufferInfo();
+ // Associate this metadata with the video frame by setting
+ // the same timestamp as the video frame.
+ metaInfo.presentationTimeUs = currentVideoTrackTimeUs;
+ metaInfo.offset = 0;
+ metaInfo.flags = 0;
+ metaInfo.size = bufferSize;
+ muxer.writeSampleData(metadataTrackIndex, metaData, metaInfo);
};
muxer.stop();
muxer.release();