Help with colour banding...

[FNi]

Hi there, I'm relatively new to the video editing world and would really appreciate some help with the basics of 'cleaning up' a video.

I've just been provided with lots of unedited 1080 footage of an event and would like to edit it into a small video but the quality of it seems very poor. I'm not sure if this is due to the camera it was filmed with, or the codec the video has been supplied in (Microsoft Video 1 CRAM - I've never even heard of it).

Here is a screengrab of the video in question: https://forum.videohelp.com/images/imgfiles/MvTOm.png

I have a few questions about it:

• Is the codec to blame for the quality, or does that look like a camera issue? Everything seems very 'pixelated'.
• Is there anyway to improve that colour 'banding' effect you see on the white background? Is that down to the compression used?
• Is there anything else you guys would recommend to generally improve the overall quality? The final edit only has to be 720p.

BTW I'm using Sony Vegas Pro 9 and would greatly appreciate any help and advice.

Thanks again.

[edDV]

Do you have access to the original camera files?

Use mediainfo to ID what you have. Post the text view of the results here.

I suspect the problem is conversion to an inappropriate codec.

[FNi]

Thanks for the reply edDV.

Here is a dump of the MediaInfo results -

General
Complete name                    : S:\p front 1.AVI
Format                           : AVI
Format/Info                      : Audio Video Interleave
File size                        : 1.49 GiB
Duration                         : 3mn 8s
Overall bit rate                 : 68.1 Mbps

Video
ID                               : 0
Format                           : MS Video
Codec ID                         : CRAM
Codec ID/Info                    : Microsoft Video 1
Duration                         : 3mn 8s
Bit rate                         : 67.3 Mbps
Width                            : 1 920 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 16:9
Frame rate                       : 25.000 fps
Bits/(Pixel*Frame)               : 1.299
Stream size                      : 1.48 GiB (99%)
Title                            : V

Audio
ID                               : 1
Format                           : PCM
Format settings, Sign            : Unsigned
Codec ID                         : 1
Codec ID/Hint                    : Microsoft
Duration                         : 3mn 8s
Bit rate mode                    : Constant
Bit rate                         : 768 Kbps
Channel(s)                       : 2 channels
Sampling rate                    : 48.0 KHz
Bit depth                        : 8 bits
Stream size                      : 17.2 MiB (1%)
Interleave, duration             : 2728 ms (68.19 video frames)
Title                            : A

Unfortunately getting the video from the original cameras isn't really an option. The crew gave the files to a middle man, who then passed them on to me. I believe the original files were on a portable hard drive but the middle man re-compressed them to fit onto several DVD's. Getting hold of the originals isn't really an option as it would take one or two weeks to get back in touch and time is of the essence.

Right now I'm open to trying anything to improve the video. It's only for web, so I don't mind bringing the resolution even below 720p if you think that would help. The white banding effect and the overall 'pixelation' of the video is what I'm most concerned about.

Thanks again for your help.

[jagabo]

CRAM (Microsoft Video 1) is a very old, inefficient codec. It uses 15 bit color (5 bits each of RGB), hence the banding.

24 bit RGB Source:


After CRAM:


The best solution is to get the intermediate to reencode with MPEG 2 or h.264 and FedEx new discs to you.

[edDV]

Why was the Microsoft Video 1 codec chosen?

The Microsoft Video 1 codec was an optimization for PC computers back in 1992 when CPU power had no headroom for MPeg video decode. All they could do was reduce bit depth from 24 bits RGB or 16 bits YCbCr to 16 or 8 bits per pixel. This causes severe quantization error but back then video on a PC was like a talking dog. You didn't complain about the dog singing in key.

Even if you apply lots of bit rate, the quantization error will still be there. You need to start over with a modern codec.

[edDV]

... It uses 15 bit color (5 bits each of RGB), hence the banding...

Yes plus 1 bit that acted as alpha or key (on or off).

[jagabo]

The gradfun2db filter for AviSynth works pretty well with that image:



Beware, it might not work as well with other shots. And may over smooth faces and other detail.

WhateverSource("filenname.ext")
gradfun2db(10)

Also, I believe that video was originally a standard defintion video. So downscaling back down to SD frame sizes won't hurt it.