> Found allowed resolutions for DVD:
>
> ,--
> | Note that the DVD format only specifically supports 720x480,
> | 704x480, 352x480, and 352x240 resolutions for NTSC
> '--
> So, assuming I can get the video recorded in one of those (which I can), do
> you know a way to skip the recoding step? It seems like the video goes
> through a lot of transformations; that can't be good for it.
The only one I've actually recorded video with (on dvd) is 720x480, so
I can't give a definitive answer about the other resolutions.
> As I can't find a way to get ffmpeg to amplify the sound during
> conversion, I instead do it externally. I separate the audio:
>
> ffmpeg -i movie.mpg -f wav temp-sound.wav
>
> check its level:
>
> sox temp-sound.wav junk.nul stat -v
>
> (returns "5.245")
>
> amplify it:
>
> sox -v 5.2 temp-sound.wav sound.wav
>
> (brings the loudest peaks to 99.14% of maximum amplitude; sox reports
> "1.009", which is consistent)
>
> and merge that with the video during conversion:
>
> ffmpeg -i movie.mpg -i sound.wav -target dvd -b 4000 -ss 0:08:12 -t 1:55:59
> -s 352x240 -map 0:1 -map 1:0 movie-352x240.vob
>
> (the original is 352x240)
>
> But, when I re-extract the sound from the vob and check its level, it's
> around half as loud as when it went in (not exactly half; then I'd be REALLY
> suspicious). Is this an artifact of the conversion to ac3, or is there some
> option that I don't notice that controls this?
When you recombine the files with ffmpeg, does it show two audio
tracks? (The original one in movie.mpg, then the one you normalized?)
If so, you may need to select the second audio track when playing
back to get the louder one.
If not, I might try doing the mapping to the new resolution with
ffmpeg first, then demuxing the video and audio using mpgdemux (part
of the mpgtx package), then normalizing the audio as you've done,
converting to ac3 or mp2, then remuxing with mplex (part of the
mjpegtools package).
Kind of a PITA, I know - such is the joy of video authoring.
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