ffmpeg question

[Joe Auty]

Okay, I think I figured this out.... almost:

ffmpeg -i /dev/cxm0 -vcodec copy -acodec copy -t 20 test_ffmpeg.mpg


Except doing this completely ignores my -t 20 and keeps on recording  
after 20 seconds... why is that?


On Apr 15, 2006, at 1:14 AM, Joe Auty wrote:

>
> 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?
>
>
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