[FFmpeg-user] make mp4 from mkv and change frame rate

[arthur brogard]

I have been trying to fix a frame rate problem I got.  I had an mp4 at the wrong rate for my t.v.  It was at 30fps and my tv wants 25fps it seems.
I got it changed with ffmpeg but the audio is out of sync.
There's suggestions for how to get it back but they seem to be suggestions for changing a fixed discrepancy in time.  I think this problem is not linear like that but the thing goes increasingly out of sync as the video plays.
So I've just thought to start from the beginning and query the community again maybe.  

I don't know that's going to help at all but that's what I'm doing here.
the beginning was a matroska mkv file.and  here's what ffprobe says about it:
Input #0, matroska,webm, from 'ACPOTBEGIN.MKV':
  Metadata:
    ENCODER         : Lavf58.29.100
  Duration: 00:25:43.27, start: 0.000000, bitrate: 931 kb/s
    Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv, bt709), 1280x720, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      DURATION        : 00:25:43.156000000
    Stream #0:1(eng): Audio: aac (LC), 44100 Hz, stereo, fltp (default)
    Metadata:
      HANDLER_NAME    : SoundHandler
      ENCODER         : Lavc58.54.100 aac
      DURATION        : 00:25:43.267000000
Any ideas how to get from there to a good file at 25fps?
:)

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