ffmpeg question

[Joe Auty]

On Apr 15, 2006, at 9:04 PM, Vayu wrote:

> On Friday 14 April 2006 23:11, Joe Auty wrote:
>> Got it!
>>
>> This bug is fixed in ffmpeg-devel...
>>
>> I think I'm good now.
>>
>>
>> I hope my thinking through this problem outloud on the list will be
>> of some use to some, and not simply spam. I'll try to be quiet now =)
>>
>
>
> Well if you're offering use to others I have two questions.
>
> What is /dev/cxm0, is it your video camera?

No, it's a Hauppauge PVR 250 (video capture card)

> What do you mean "fixed in ffmpeg-devel", do you mean you can  
> compile a newer
> version?

My particular problem was an issue in the FreeBSD ffmpeg port, but  
not in the FreeBSD ffmpeg-devel port.



>
>
>
>> On Apr 15, 2006, at 1:53 AM, Joe Auty wrote:
>>
>>> 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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>>>
>>
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