theora - Feb 2007 - ogg file format specification

Hello all,

I'm coding (trying to code should be better) a soft in python to analyze
video. (scene change, edge, line, motion) and i want to use ogg file. So i
got a few questions :

To analyze the video i need an acces to the video data (the array of pixel)
and i'm wondering if i can acces it directly, i mean by my own or do i
really need to use the decode process to get an array of RGB values ?
And if i need to use the decode procees, will pymedia (http://pymedia.org/)
allow this ?

If i can access the video data by myself (which is better for the computer's
performance):
I didn't find the file format specification i'm talking about the size
in
bit of the header (and how can i read it) and the size of the 'footer'
if
theora use one. and stuff like that.
So where can I find it ?


I have read the specification of theora and spend a long time looking over
internet for this information but i couldn't find anything except that the
header does not contain the number of frame because theora is supposed to be
usefful to streaming.
To my mind, most of the streamed video are finished files, there are a just
a few streaming of pure video stream (like webcam, or tv channel) and the
fact is knowing the number of frame (when it's possible) is really usefull.
So why don't you put it in the header and give it a negative value for
example when it's an unfinished video stream?

Thank you for reading me, I'm sorry for my bad english

Sincerly,


Corentin
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Hi Corentin,

it appears you've already found the theora specification. You may also
find the API reference useful, it is also listed on theora.org.

The Ogg Theora data needs to be decoded in order to access frame data.
I do not know if pymedia supports Ogg Theora. Perhaps you would find
pygst (the python bindings GStreamer) useful.

cheers, and good luck,

Conrad.

On 23/02/07, Corentin allard <callard@ece.fr>
wrote:
> Hello all,
>
> I'm coding (trying to code should be better) a soft in python to
analyze
> video. (scene change, edge, line, motion) and i want to use ogg file. So i
> got a few questions :
>
> To analyze the video i need an acces to the video data (the array of pixel)
> and i'm wondering if i can acces it directly, i mean by my own or do i
> really need to use the decode process to get an array of RGB values ?
> And if i need to use the decode procees, will pymedia (http://pymedia.org/)
> allow this ?
>
> If i can access the video data by myself (which is better for the
computer's
> performance):
> I didn't find the file format specification i'm talking about the
size in
> bit of the header (and how can i read it) and the size of the
'footer' if
> theora use one. and stuff like that.
> So where can I find it ?
>
>
> I have read the specification of theora and spend a long time looking over
> internet for this information but i couldn't find anything except that
the
> header does not contain the number of frame because theora is supposed to
be
> usefful to streaming.
> To my mind, most of the streamed video are finished files, there are a just
> a few streaming of pure video stream (like webcam, or tv channel) and the
> fact is knowing the number of frame (when it's possible) is really
usefull.
> So why don't you put it in the header and give it a negative value for
> example when it's an unfinished video stream?
>
> Thank you for reading me, I'm sorry for my bad english
>
> Sincerly,
>
>
>  Corentin
>
>
>
>
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> theora mailing list
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> http://lists.xiph.org/mailman/listinfo/theora
>
>