Replacing the original sound from an mpeg file

[mpolo]

I have an mpeg with wonderful quality, but the wrong language. I have an avi with the correct language. I already extracted the audio into an ac3 format. My problem is how to get this ac3 audio into the existing video.

I tried using ffmpeg with -b 90k (mplayer reports that the bitrate is 90000) to convert to m2v so that I could use mplex with the m2v and ac3 files. This "works", sort of -- it's even in sync; however, there is a remarkable loss of quality on the video.

Is there something I'm missing? How can I multiplex just the video from an existing mpeg with another audio file?

[mpolo]

Umm.. Sorry. Idiotic question. The bitrate should have been 9000k. Stupid stupid stupid.

So, in case this come up for someone else:

ffmeg -b 9000k -i my_mpeg.mpeg my_mpeg.m2v
ffmpeg -i my_avi.avi -ab 12800 -ar 44100 my_avi.ac3
mplex -f 8 -o final.mpeg my_mpeg.m2v my_avi.ac3

[mpolo]

Umm.. Sorry. Idiotic question. The bitrate should have been 9000k. Stupid stupid stupid.

So, in case this come up for someone else:

ffmeg -b 9000k -i my_mpeg.mpeg my_mpeg.m2v
ffmpeg -i my_avi.avi -ab 12800 -ar 44100 my_avi.ac3
mplex -f 8 -o final.mpeg my_mpeg.m2v my_avi.ac3

[Milena]

Hi

I had exactly the same problem a while back. Avidemux worked great, it can save the audio from one video file and then you add it to another. no quality loss as it simply copy the video and add the new audio track to the output file, getting it 100% sync is not a problem either. avidemux is really one of my favorite tools.

[psyklops]

Does it have to be MPG? You might have some more flexibility converting and muxing into a different format.

In any case, you can try the following:

ffmpeg -i <video_source.mpg> -i <audio_source.ac3> -target pal-dvd -sameq -map 0:0 -map 1:1 <video_output.mpg>

The "pal-dvd" preset configures your audio into AC3 already at a DVD compliant bitrate, and "sameq" tried to maintain the same quality for your video.