[mpeg2] Re: colour offsets

[Frank Rosengart <rosengart@convergence.de>]

Warren Young wrote:
> Frank Rosengart wrote:
> 
>>
>> JVC-DV500 camera, put it into EBU-bars mode and wired the Y/C output of 
> 
> [snip]
> 
>> white           244-247-244
>> yellow  185-190-0 
> 
> 
> Hmmmm...looks like something in your video chain is stretching the color 
> gamut to 0-255.  Video signals are standardized so that there are signal 
> ranges understood to be "brighter than white" and "darker than black". 
>  You should only be seeing a range of about 16-235 when you map 
> calibrated video to RGB.
> 
> I would guess that Premiere is doing the gamut stretch so that the video 
> looks nice and saturated on your monitor.  Try DVD2AVI instead. 

I tried mplayer with -vo png and then Photoshop. Got the same results.

> If, after following this procedure, you still see that 0-247 range, your 
> Kfir board is definitely miscalibrated.

The next days I will try another KFir-card. But I think

> I then took my _Video Essentials_ DVD, ripped the SMPTE color bars 
> pattern off of the disc, and found:
> 
> white:   235, 235, 235
> black:   16, 16, 16

should be a starting point to software-calibrate the KFir boards to 
match the correct colours. Maybe I should try the composite way.



#frank