[XviD-devel] little image error?

Michael Militzer michael at xvid.org
Wed Mar 17 14:10:09 CET 2004


Hi,

Quoting Christoph Nägeli <chn at kbw.ch>:

> I got some little blocks in the encoded movie that seem to have a wrong 
> color.
> I first thought that my altivec code is buggy but using plain c, these 
> blocks have the wrong color, too.
> 
> 
> Can someone have a look at the picture and tell me if I'm right?
> 
> The picture can be seen at:
> http://people.ee.ethz.ch/~naegelic/Error.jpg

This looks like something related to quantization or coefficient clamping.
I'd try the following (in addition to what Christoph already suggested):

- Compile without optimizations and then try again
- If you have trellis enabled, try without trellis
- If you used h.263 quant, try MPEG or vice-versa
- If you've used a custom MPEG matrix, try with the default one
- Make sure that your c-code actually is a vanilla rc3 copy (I often 
  believe I have an unmodified copy but simply forgot about a 'trivial'
  change I made earlier...)

BTW: How are you _decoding_ the video. Make sure you use XviD and not
ffmpeg, make sure that the decoder also only uses c-code...

Michael


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