ffmpeg question

[Joe Auty]

On Apr 15, 2006, at 1:10 AM, Jacob Meuser wrote:

> On Fri, Apr 14, 2006 at 11:54:18PM -0400, Joe Auty wrote:
>> Hello,
>>
>> Doing a:
>>
>> cat /dev/cxm0 > myvideo.mpg
>>
>> produces great mpeg2 video... However:
>>
>> ffmpeg -i /dev/cxm0 -t 10 test_ffmpeg.mpg
>>
>> produces 10 seconds of mpeg1 video that doesn't look as good.
>>
>>
>> I've tried adding -f <format> and -vcodec options with -s 640x480,
>> but I just can't seem to find something that will reproduce my raw
>> feed without errors, loss of picture, the size being off, or
>> reverting back to mpeg1.
>>
>> To save me a little further time in just random trial and error, can
>> anybody hook me up with the combination I need?
>
> sorry, but what exactly are you trying to do?  what is lacking with
> the cat command?
>
> most likely, if you are running a transcoder (like ffmpeg, mencoder
> or transcode), it is decoding the input into raw YUV or RGB and then
> back to MPEG.  this is a lossy and time/cpu consuming process.
>

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.

According to Quicktime's Get Info, the cat files are mpeg2... I'd  
like to know the best way to preserve the same quality from the cat  
command using ffmpeg.

Am I starting to make sense now?