How to avoid banding in a gradient on a youtube video

[Strob]

If you watch this video you will see an obvious banding in the gradient color at the bottom of the blue flame (I created this effect in CG). Do you have any trick in the compression to avoid this. Before compressing it looks smooth. Adding noise does not remove all the banding neither.

http://www.youtube.com/watch?v=T6e6KzsISoA

[Soopafresh]

Is your source file in RGB color space? Banding can often occur in the RGB-YUV color space transfer. Worst of all, lossy codecs such as h264, MPEG2, etc are notoriously bad at encoding smoke, clouds, water. Add to it your smokey looking source and the Youtube video conversion and it's a recipe for colossal disaster of the first magnitude.

[jagabo]

You can't completely eliminate the banding because youtube reencodes with very low bitrates. All you can do is avoid gradients or add random noise.

[guns1inger]

That is an ugly test for banding. Very hard on the encoder. I agree that in this case, some film grain or noise would help out, but that comes with the trade off that it requires a higher bitrate to avoid blocking.

[Strob]

thanks all,

My source is CG so I can choose the color space. Which one would be ideal?

I will try to add noise until the banding disappear.

If I can get something like this video I would be happy: http://www.youtube.com/watch?v=kBX6JyesRzI

[Soopafresh]

YUV color space.

Rule out the Youtube encoder by uploading your clip to vimeo and compare.

[Strob]

Do you know how to set YUV in after effect?

[jagabo]

I don't know AE but look for YUY2, YV12, or similar settings. Rendering to a YUV format probably won't make any significant difference. Even if AE lets you output YUV it probably renders in RGB then converts to YUV for output. So it won't be any different than what what your doing now.

If you can render with a higher color depth, say 16 bits for each channel, and add noise while in that color depth, you'll get much better results than adding 8 bit noise to 8 bit color.

[poisondeathray]

AE functions in RGB

You can export an RGB format , but youtube will re-encode to Y'CbCr (YUV) format in 8-bit precision

The banding is more a function of bit depth (8 bit video, or 8 bits per channel (8R,8G,8B) ) , than RGB vs. Y'Cb'Cr , because there are only 2^8 "shades" for each channel or 256. So gradients don't have smooth transitions.

You can have 10-bit Y'Cb'Cr video for example, and your banding would disappear. Because color is expressed in 2^10 "shades" (or 1024)

In AE you can use 16-bit or 32-bit precision , and export a 16 or 32-bit image sequence (e.g. tiff). You can even export 10-bit YUV uncompressed (v210); but that doesn't matter, because the weak link here is YOUTUBE

The only thing you can try to do is dither the video.

[Strob]

Ok thank all. That's what I was thinking.