[theora-dev] Ogg files incompatible

[Id Kong]

> Date: Fri, 12 Feb 2010 08:30:50 -0500
> From: tterribe at email.unc.edu
> CC: theora-dev at xiph.org
> 
> Id Kong wrote:
> > However, something is still wrong.  My DirectShow filter, ffdshow, can't
> > play these ogg files at all and, instead, show a very short sequence of
> > random colours, crashing most of the time.  VLC player can play these
> 
> Unless it's using a very recent build of ffmpeg, ffdshow does not
> properly support Theora. Its decoder was limited to the old VP3 subset,
> and did not support any new things we included in the spec, despite the
> fact that it was published in 2004. It only worked because the mainline
> encoder didn't use any of these extensions either, until the recent 1.1
> release. Most of these issues have been fixed (thanks to David Conrad),
> though ffmpeg still does not properly support cropping rectangles with a
> non-zero offset for video that doesn't have a multiple-of-16 frame size
> (they don't support this feature for H.264, either). Have you tried our
> DirectShow filters: http://www.xiph.org/dshow/ ? If these do not work,
> we would like to know.

	Thank you for this information.  It's an eye opener!

> > files but I'm afraid that's not good enough for my purposes.  My
> > ultimate goal is to upload these theora videos to YouTube but they have
> > the same problems as ffdshow.
> 
> Right. As far as I know, they are using some old build of ffmpeg to
> transcode Theora. This situation is, shall we say, less than ideal.

	Indeed, it's much less than ideal.  Do you know where I can find source code for older versions of libtheora?  I can't find any on the site and a Google search wasn't fruitful.  Since my ultimate goal is to upload video to YouTube, what matters is that it actually work, so compatibility is my priority...

> > The reason I still think the problem is with my code is that both
> > players and YouTube can play other ogg files not made by my software.
> >  Here are two examples:
> > 
> > http://www.osnews.com/img/19020/qvga.ogg
> > http://www.osnews.com/img/19020/720p-theora.ogg
> 
> Vendor: Xiph.Org libTheora I 20071025 3 2 1
> 
> These are using an encoder from before the 1.1 release, which is why
> they work with the broken ffmpeg.
	If I'm not mistaken, they were encoded using ffmpeg2theora so that it's compatible with (the broken) ffmpeg shouldn't be surprising.  So basically, no one's using the "new" specification...

> > Can you explain this further please?  Can't they simply assign their new
> > stream a number unique to any existing one in the ogg file?
> > Thank you very much...
> 
> I'm talking about tools that edit existing streams. Assigning a stream a
> new serial number means rewriting all of the pages, and computing a new
> checksum for them.

	I was talking about editing existing streams.  Assuming whatever made the ogg file gave each stream a unique but non-random serial number, if I wanted to add to it, can't I simply choose another non-random serial number that's unique to whatever numbers are already used in the ogg file?  What am I missing here?	Thank you... 		 	   		  
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