Green blot on satured colors: how do I get rid of these kinda artifacts?

[danpos]

The title thread already speaks itself. The content is a short clip from analog TV capture. Used MJPEG VFW. Here's the Link (http://www.megaupload.com/?d=8Q0D4XI5).

Any advise for solve the issue is highly appreciated.

TIA,

[IanB]

The YUV data in the sample file has the V channel exceeding the valid range and the overflow has caused wrapping of the values. The Y channel also exceeds limits as well but fortunatly does not appear to have wrapped. Strangely the U channel appears okay.

i.e. The ADC hardware has tried to express a value greater than 255, eg 258 and because there are only 8 bits to store the data the value 2 is stored instead. Because this has happened in the V channel peak reds become strong green. The damage to the captured file cannot be recovered, you will have to recapture.

If the driver for your capture card has Contrast, Brightness and Saturation controls, based on the peak values seen in you sample, increase brightness by 6%, decrease contrast by 14% and decrease saturation by more than 13%.

To check further captures make sure your MJPEG codec decodes to YUY2 or YV12 color space and use ColorYUV(Analyze=True) to check the range of values occuring in your data stream. The Y channel peaks must be between 16 and 235. the U & V channel peaks must be between 16 and 240.

[danpos]

@IanB

Thank you so much for the very well explained and technically justified answer.You've learned me a lot with this great post. :goodpost:

In the future I will follow yours advises.

Cheers,