How to convert AMR audio track to something else with the video unchanged

[rlew]

I have a new Samsung phone which records usable movies in VGA resolution. But I'd like to be able to play back those movies on stand-alone DVD players (e.g. from a USB stick). I have tried three, and they all play back the video fine, but report an unsupported audio codec. I'd like find a solution to convert the audio track on such a file but without modifying the video in any way. So far I have downloaded several conversion utilities but there was no option to just leave the video as is, and the resulting video file tends to be not as good as the original.

Here is what winamp reports for the audio and video tracks of one original file. The clip is only 53 secs long, so maybe the fps is not really correct and should be 23 (?)

Audio AMR 13 kbps, 8000 Hz (I'm guessing that's just a single channel)
Video MPEG-4, 384 kbps, 640x480 (VGA) @ 22.796981 fps

Now, I've located this thread: https://www.videohelp.com/forum/archive/please-help-trying-to-convert-audio-only-to-mpe...3-t325394.html - seemed like a good way to proceed and I'd be willing to try and play with the command line switches, but it is over two years old and the target files are no longer available...
But I don't need a batch solution, I only expect to need to convert a file once a month or so.

[aedipuss]

the video is non standard also at that framerate. you might want to convert both vid and aud to a more normal standard. Mobile Media Converter might work. you could also try avidemux.

[rlew]

the video is non standard also at that framerate. you might want to convert both vid and aud to a more normal standard. Mobile Media Converter might work. you could also try avidemux.

Many thanks, aedipuss!

Mobile Media Converter was one of the apps I'd tried before, but it has no option to leave the vid as-is. Tried a dozen different configurations and either got a degraded pic quality (in particular, in the early 2 secs the colours kind of tuned in), or else an error.

But AviDemux worked great, set Video to "Copy", Audio to mp3 with lowest available bitrate (56kbps) - I guess no point in going higher if the original was only 13kbps?

Thanks too for the tip on adjusting the framerate, but I don't want to do that if the original is fine. This wouldn't give me an improved pic quality, would it?

[aedipuss]

no, anything other than "copy" video will re-encode it, thereby losing a bit of quality. if it works fine as is for you then i'd leave it alone. 56kbps is more than enough as you thought.