diff options
-rw-r--r-- | media/libstagefright/MPEG4Writer.cpp | 39 |
1 files changed, 36 insertions, 3 deletions
diff --git a/media/libstagefright/MPEG4Writer.cpp b/media/libstagefright/MPEG4Writer.cpp index ba1e218..e6c2f7e 100644 --- a/media/libstagefright/MPEG4Writer.cpp +++ b/media/libstagefright/MPEG4Writer.cpp @@ -1541,20 +1541,52 @@ status_t MPEG4Writer::Track::threadEntry() { int32_t isSync = false; meta_data->findInt32(kKeyIsSyncFrame, &isSync); + /* + * The original timestamp found in the data buffer will be modified as below: + * + * There is a playback offset into this track if the track's start time + * is not the same as the movie start time, which will be recorded in edst + * box of the output file. The playback offset is to make sure that the + * starting time of the audio/video tracks are synchronized. Although the + * track's media timestamp may be subject to various modifications + * as outlined below, the track's playback offset time remains unchanged + * once the first data buffer of the track is received. + * + * The media time stamp will be calculated by subtracting the playback offset + * (and potential pause durations) from the original timestamp in the buffer. + * + * If this track is a video track for a real-time recording application with + * both audio and video tracks, its media timestamp will subject to further + * modification based on the media clock of the audio track. This modification + * is needed for the purpose of maintaining good audio/video synchronization. + * + * If the recording session is paused and resumed multiple times, the track + * media timestamp will be modified as if the recording session had never been + * paused at all during playback of the recorded output file. In other words, + * the output file will have no memory of pause/resume durations. + * + */ CHECK(meta_data->findInt64(kKeyTime, ×tampUs)); + LOGV("%s timestampUs: %lld", mIsAudio? "Audio": "Video", timestampUs); //////////////////////////////////////////////////////////////////////////////// if (mSampleSizes.empty()) { mStartTimestampUs = timestampUs; mOwner->setStartTimestampUs(mStartTimestampUs); + previousPausedDurationUs = mStartTimestampUs; } if (mResumed) { - previousPausedDurationUs += (timestampUs - mTrackDurationUs - lastDurationUs); + int64_t durExcludingEarlierPausesUs = timestampUs - previousPausedDurationUs; + CHECK(durExcludingEarlierPausesUs >= 0); + int64_t pausedDurationUs = durExcludingEarlierPausesUs - mTrackDurationUs; + CHECK(pausedDurationUs >= lastDurationUs); + previousPausedDurationUs += pausedDurationUs - lastDurationUs; mResumed = false; } timestampUs -= previousPausedDurationUs; + CHECK(timestampUs >= 0); if (mIsRealTimeRecording && !mIsAudio) { // The minor adjustment on the timestamp is heuristic/experimental // We are adjusting the timestamp to reduce the fluctuation of the duration @@ -1590,8 +1622,8 @@ status_t MPEG4Writer::Track::threadEntry() { } } - LOGV("time stamp: %lld and previous paused duration %lld", - timestampUs, previousPausedDurationUs); + LOGV("%s media time stamp: %lld and previous paused duration %lld", + mIsAudio? "Audio": "Video", timestampUs, previousPausedDurationUs); if (timestampUs > mTrackDurationUs) { mTrackDurationUs = timestampUs; } @@ -1873,6 +1905,7 @@ void MPEG4Writer::Track::writeTrackHeader( // First elst entry: specify the starting time offset int64_t offsetUs = mStartTimestampUs - moovStartTimeUs; + LOGV("OffsetUs: %lld", offsetUs); int32_t seg = (offsetUs * mvhdTimeScale + 5E5) / 1E6; mOwner->writeInt32(seg); // in mvhd timecale mOwner->writeInt32(-1); // starting time offset |