[mythtv-users] MonoChrome (B+W) Recordings

[Dan Seddon]

Hi Brian
Nice idea - but I think this kind of thing is already fairly well dealt 
with in the video compression. As far as I'm aware (and I'm no expert, 
but I think I'm right on this) video is stored in "yuv" format where  
"y" is the luma and u&v are kinds of difference channels for 2 of the 3 
colours (where the 3rd can be worked out from the first two - giving the 
full chroma information). In 4:2:2 video, the chroma is stored at half 
the resolution of the luma, partly because the eye is less sensitive to 
it and colour does tend to vary less than luminance - so adding colour 
already only doubles the amount of data, rather than triple it. Then in 
digital video this information is compressed which may mean information 
which is repeated is saved in "short hand" or information which is less 
significant is thrown away. In the first case, the chroma information 
tends to compress better than the luma as is varies less (a red apple 
may only have a small variation of red in it, but a lot of tonal 
changes) - which means the chroma might only make up a small fraction of 
the data in the first place, but in the case of BW this would obviously 
be shrunk even further as you'd hope these channels would be practically 
blank.

Cheers

Dan
> It occurs to me that I record a lot of Black-and-White programs, and  
> that they are recorded as color video, thus wasting a lot of space.
>
> I figure that to actually record the programs as B+W would require  
> changes to the drivers, if not the firmware, of the PVR cards, and is  
> probably not practical.
>
> But transcoding them after the fact to eliminate unneeded chroma  
> information might be possible.
>
> Does anyone know of a way to transcode an mpeg-2 file to a pure B+W  
> one? Seems like a lot of space could be saved.
>
> Brian Wood
> beww at beww.org
>
>
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>