FFmpeg-混合视频和音频时大文件的ANR

Question

This command

ffmpeg -i video.webm -i audio.m4a -c copy output.mkv

will always produce an ANR error in android at the end of the conversion for any large files, say greater than 700mb.

The ANR error is produced only at the finishing end of the conversion process after the output has been successfully generated, not in the middle or at the beginning etc.

So I suspect it has got to do with some I/O stuff at the end. Can someone please shed some light into this, and help eliminate this ANR problem?

Answer 1

By default, ffmpeg produces progress output ~every 500ms. The way FFmpeg-Android treats this output, it returns the progress message to your onProgress() callback, and also appends all these (relatively short) messages to a String, which is returned in onSuccess() .

What happens is, for a large video file the memory may get exhausted, or at least the Garbage Collector will work pretty hard. These String manipulations happen on the Main thread, which can easily cause ANR.

As a quick workaround, you can pass -nostats to the ffmpeg command line:

ffmpeg -i video.webm -i audio.m4a -c copy output.mkv -nostats

To resolve the issue, look at https://github.com/bravobit/FFmpeg-Android/pull/128 .