Mediamuxer produces corrupted video when samples are written in batch

Question

I'm trying to use Android's MediaMuxer and MediaCodec to produce MP4 videos.

If I drain frames from the codec directly to the muxer by calling writeSampleData(), everything works fine and the correct video is produced.

But if I try to first store these frames on an array and decide later to send them to the muxer, I'm unable to produce a working video, even if the presentation timestamps are correct.

For some reason, it seem that the mediamuxer output depends not only on the presentation timestamps, but also on the actual time "writeSampleData" is called, although it's my understanding that having the correct timestamps should be enough.

Can anyone shed some light on this issue?

Answer 1

Thanks mstorsjo and fadden . I had actually a combination of errors which didn't allow me to understand what was really going on. Both your questions led me to the correct code and the conviction that using writeSampleData() was not time sensitive.

Yes, I was getting the wrong buffers at the first time. The problem was not initially noticeable because the muxer was writing the frames before the buffers got rewritten. When I introduced the delays and decided to duplicate the buffers contents, I hit another issue (basically a race condition) and concluded it was not the case.

What this code does (for the SmartPolicing project) is capture video and audio to create a MP4 file. I could use MediaRecorder (this was the initial solution), but we also wanted to intercep the frames and stream the video via web, so we dropped the MediaRecorder and created a custom solution.

Now it is running smoothly. Thanks a lot, guys.

Answer 2

您确定确实存储了要写入帧的完整数据，而不仅仅是缓冲区索引吗？