On Mon, 9 May 2005, Dik Takken wrote:
I did see this new syntax after entering 'yuvdenoise -h' but it did not seem to work either. The reason turns out to be that I entered:
... | yuvdenoise -Y 0 -U 0 -V 0 | ...
to try it and it crashed on that, so I got the impression that this wasn't
Definitely need to check for 0 to avoid the crash. If the documentation is updated to explicitly state the values are integers then I think that is sufficient.
I did a bit more experimenting with chroma noise filtering, and I learned a new trick while doing it: Use MPlayer to turn down the contrast setting of the XVideo subsystem and set the saturation real high. The 'yuvplay' utility does not touch XV settings so it will have the same display settings as MPlayer has. Now all that is left to see is pure chroma data.
Next, I tried to get rid of all the noise in the chroma data. The CCD induced chroma noise is quite heavy in the low-light scene I use for testing. First I tried spatial filtering only by using y4mspatialfilter and yuvmedianfilter. This approach failed, because the groups of adjacent pixels that change color from one frame to the next are too large. Removing the noise would require using a filtering radius of > 15 pixels or so, which blurs the chroma channel too much.
I managed to denoise the scene properly by using y4mdenoise like so:
smil2yuv file.dv | y4mdenoise -t 0 -z 0 -T 12 -Z 12 | yuvplay
The downside of using y4mdenoise is that it takes 5 seconds to process a single frame on my machine. Even higher error thresholds do not make it much faster. Using yuvdenoise is about ten times faster, and gives slightly better results, doing:
smil2yuv file.dv | yuvdenoise -Y 1 -U 1 -V 1 -y 1 -u 10 -v 10 | yuvplay
But this also has a downside: It touches the luma data too because, AFAIK, there is no way to completely disable luma processing in yuvdenoise.
Could yuvdenoise be fixed to ignore the luma channel when the threshold is zero? It seems to me that it would be the ideal chroma noise filter.
Cheers,
Dik
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