[theora] Loseless Video Codec

Stefan Gürtler mail at stefan-guertler.de
Fri Jan 8 14:05:26 PST 2010

Philip Jägenstedt schrieb:
> On Fri, Jan 8, 2010 at 09:23, dos386 <dos386 at gmail.com> wrote:
>>> P.S. Opera 10.5 just added support for Ogg *thumbs up*
>> http://my.opera.com/ODIN/blog/opera-10-5-pre-alpha-build-released-here-is-whats-new
>>> Will Opera 10.50 include support for playing Ogg Theora video using the HTML5 video tag?
>>> @Petter: Yes, we're working to include it in future builds.
>> I can't find ^^^ such info :-|
> http://my.opera.com/core/blog/2009/12/31/re-introducing-video
>>>> Could you elaborate on this?  Standard MJPEG is necessarily lossy.
>>> Judging by the size and image quality
>>> it actually __is__ __lossless__ too (the bitrate setting as no effect). I'm
>>> sure ljpeg can be done with mencoder etc too.
>> It would be maybe good to make sure that the competitor __IS__
>> lossless by comparing the frame bitmaps.
> The video has already been captured, so there's no helping my data if
> ffenc_ljpeg isn't lossless (which would be a bit surprising, but
> possible). But in any case, I have really wanted a tool to verify that
> two videos are in fact pixel-identical and perhaps to show visual
> diffs. Does anyone know of such a tool?

How to ensure that two clips have identical information: Decode each 
frame to uncompressed pictures and calculate a md5sum. MPlayer has a 
video output driver, which calculates the md5 sums of the frams.
See mplayer -vo help

For showing the differnce between two clips i would suggest to look into 
the avisynth frame server, e.g 

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