Normalize Your Video With FFmpeg

It’s been a while since I’ve updated my blog. I didn’t encounter any weird things until last week.

At Movideo, we’ve been haunted by videos that goes out of sync with it’s audio. The symptom goes something like this:

1. Plays a dynamic bitrate video that was encoded using Movideo’s Encoder application.
2. In the beginning, audio and video is in sync.
3. A crackling noise appeared and then the audio and video goes out of sync.

We’ve decided to use MEncoder to normalize the original video which is in .mov format.

The command

mencoder -ovc copy -af volnorm=1 -oac libmp3lame input.mov -o output.mov

creates a mov file which Quick Time won’t recognize at all. Tried viewing it with Windows Media Player and there’s audio but no video. After that, I upload the video via Movideo’s Admin interface. The re-encoded video still goes out of sync.

The solution to this is to re-encode the audio with FFmpeg with

ffmpeg -i input.mov -vcodec copy -acodec libmp3lame output.mov

Now, output.mov can be viewed by Quick Time and works fine on Windows Media Player. Then, I tried uploading the output.mov via Movideo’s Admin interface and the video doesn’t go out of sync anymore.