[theora] [bug?] strange colors

[Gregory Maxwell]

On Sun, Feb 14, 2010 at 12:49 PM, Tom Sparks <tom_a_sparks at yahoo.com.au> wrote:
> I have been transcoding a group of panoramic videos using ffmpeg2theora 0.26
> i just completed transcoding Naples Cycle HDV.vwmovie
> the resulting video has some strange colors in it
>
> the source video can be got from http://www.eyesee360.com/videowarp/examples/
> the resulting images and the theora file can be download from http://www.lightningridgecommunity.com/images/
>
> tom at tom-laptop:~/Videos/krpano$ ffmpeg2theora -V1000k -A64k "Naples Cycle HDV.vwmovie"
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Naples Cycle HDV.vwmovie':

Hi Tom,

I don't think it is a _bug_, I think its just poor quality. You're
encoding 1554*590 4:2:0 @25fps into 1-megabit, which is 0.04 bits per
pixel. Nothing is going to look great at that low a rate, especially
high motion with a strictly buffer limited stream.  Your H.264 input
is at ~9megabits and even that doesn't look all that perfect.

I think all you're seeing in this case is that the encoder is running
out of bits so thoroughly that it is making the color information very
blocky. This chunkyness produces the somewhat off colors.

The current development encoder is more intelligent about bit
allocation decisions in smooth areas. When I combine the development
encoder with a two-pass encode I get this:

http://myrandomnode.dyndns.org:8080/~gmaxwell/theora/Naples_Cycle_ptalarbvorm_twopass.ogv

and I think that looks a lot better.