[FFmpeg-devel] Irregular codec

[Jesse L. Zamora]

M?ns Rullg?rd wrote:
> Benjamin Larsson wrote:
>   
>> Kostya wrote:
>>     
>>> On Mon, Jun 30, 2008 at 06:44:55AM -0400, Jesse L. Zamora wrote:
>>>
>>>       
>>>> Benjamin Larsson wrote:
>>>>
>>>>         
>>>>> On Fri, Jun 27, 2008 at 07:58:11PM -0400, Jesse L. Zamora wrote:
>>>>>
>>>>>
>>>>>           
>>>>>> Hello All,
>>>>>>
>>>>>> I've been writing a demuxer and a decoder for the SMV format (SigmaTel
>>>>>> Motion Video) for ffmpeg. It begins with a WAV file, then the SMV header
>>>>>> afterwards, then an array of jpegs. I was trying to get my demuxer to be
>>>>>> able to read the SMV header, but since it's practically in the middle of
>>>>>> the file, the buffer is not that big! So I can't read the header through
>>>>>> the buffer. How can I somehow read in the middle of the file with the
>>>>>> demuxer_probe(AVProbeData *p) function to be able to read the header
>>>>>> (especially with demuxer_read_header())?
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> Xtreme Kommander
>>>>>>
>>>>>>
>>>>>>             
>>>>> Hi, can you derive that it is a SMV file from the wav header ?
>>>>>
>>>>> MvH
>>>>> Benjamin Larsson
>>>>>
>>>>>           
>>>> I was hoping that I could, but it seems that the WAV header has only
>>>> fields for WAV.....and the SMV header is in the middle of the file.
>>>>
>>>> Xtreme Kommander
>>>>
>>>>         
>>> Since detecting SMV would require seeking after WAV file end (size
>>> specified in RIFF header), it can't be done during probe stage.
>>>
>>> I see three ways here:
>>> 1) patch WAV demuxer to handle SMV files as well (not nice at all)
>>> 2) make WAV demuxer detect SMV files and print warning ("hey, use -f smv")
>>> 3) make SMV demuxer and hope users will add -f smv by themselves
>>>
>>> and there's always
>>> 0) SMV? What's that?
>>>
>>>       
>> Well .smv and wav header -> SMV file, should work also.
>>     
>
> What if it really is just a plain wav file, only with a funny name?
>
>   
Yeah, it's probably not good to depend on the filename. The only *safe* 
way to be sure is to see if the SMV header exists.

Xtreme Kommander