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Banding issue using H264

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Chris Blair
Banding issue using H264
on Feb 19, 2009 at 6:32:26 am

We have Carbon Coder (which is a great tool), and have started doing some H264 encoding for flash. The majority of stuff looks absolutely great, but we're having a problem with shots that show blue skies with puffy clouds. These shots, (and these shots only) have terrible banding in the sky as well as some pretty bad artifacting.

What's more, shots with completely blue skies with no clouds (even ones with a gradient in the sky) encode beautifully.

Any tips to eliminate this issue form the blue, cloud filled skies?
Source content is 720P quicktimes using the Quicktime DVCProHD codec, so the source quality is very high. We don't typically mess that much with Carbon Coder's settings, but we're encoding with:

H264
two pass
streaming
29.97 fps
non-interlaced (the source footage is also non-interlaced HD)
750kb/sec avg bitrate with 1000 max.

We've tried using a couple of filters to alleviate the issue:

Median – designed to improve picture quality by removing single-pixel defects without affecting the sharpness. This is similar to a despeckle filter.

Temporal Noise Reducer – This filter removes noise by using temporal noise reduction. Temporal noise reduction is effective for removing noise in the image.

We've used these filters on a lot of other footage with good results. But they have little affect in this case.

These are 30 second files and they end up being about 3.3MB in total size and stream fine on a reasonably fast connection.

There are no keyframe options with this present, nor any options to add keyframing. The only item I see that might fix this is to raise the maximum burst bitrate from 1000 to say 1250. Unless someone else has some suggestions. Videos without blue puffy skies look absolutely flawless with no noticeable artifacting or color banding.


Chris Blair
Magnetic Image, Inc.
Evansville, IN
http://www.videomi.com


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Daniel Low
Re: Banding issue using H264
on Feb 19, 2009 at 7:59:35 am

Carbon Coder is one of my favorite encoders.

Are you using the Quicktime H.264 target or the Mainconcept based target?

What frame size is your output?




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Chris Blair
Re: Banding issue using H264
on Feb 20, 2009 at 2:22:10 am

Daniel,

It IS our favorite...and Procoder, essentially made by the same software engineers, is a close second if you're on a budget.

We figured the issue out. We're using the H264 export preset, which offers you three containers or wrappers (is that the right term?), F4V, MP4, MP2 and Raw.

We selected MP4 because that's what the ad agency uses on it's website. The settings are pretty complex and use some really unfamiliar (to me at least) terminology...but there's one check box that sounds vaguely like keyframing (it was called something like "frame seeking"), so I checked it...and voila, ZERO banding and absolutely beautiful output.

We had done all our H264 up to this point in a great little program called Flash Video Studio ($59 with great codec and skin support), which has fewer tweaks available and was having the same banding issue (although not as severe) in the blue sky with clouds.

The H264 quality (using any of the file extensions listed above) looks stunning, and a :30 spot came in at 3MB.





Chris Blair
Magnetic Image, Inc.
Evansville, IN
http://www.videomi.com


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