ffmpeg question

[Oliver Fromme]

Joe Auty <joe at netmusician.org> wrote:
 > The cat command works perfectly, but I'm trying to script it, and  
 > since you can use ffmpeg to specify how many seconds of footage to  
 > capture I'm trying to make this work.

#!/bin/sh -
DURATION=20
DATESTAMP=$(date +%Y-%m-%d)
cat /dev/whatever > /foo/bar-${DATESTAMP}.mpg &
CATPID=$!
sleep $DURATION
kill $CATPID

 > According to Quicktime's Get Info, the cat files are mpeg2...

Yes.  What exactly is wrong with MPEG-2 in your opinion?

 > I'd  like to know the best way to preserve the same quality
 > from the cat command using ffmpeg.

ffmpeg decodes from MPEG format and then re-encodes it,
which is lossy, so you can never preserver the same quality.
That is, unless you use "copy" for the codec, which means
it won't decode/encode anything -- but then it's just like
teh cat command anyway, with a hundred times the overhead.

 > Am I starting to make sense now?

I'm not sure.  :-)

Best regards
   Oliver

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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