[mythtv-users] Really washed out picture since upgrade to 0.24.0

[Paul Gardiner]

On 21/11/2010 13:59, Dan Christensen wrote:
> Can someone summarize the issues here regarding studio levels?  Maybe
> someone can create a FAQ for myth about this?
>
> - What are studio levels?

When YUV is converted to RGB, you get values from 0 to 255 for each gun.
But not all the values are used. 16 is actually the blackest black, and
235 is the brightest white. Any values below 16 are called blacker than
black, and I presume they are supposed to be clipped. Values above 235
might be clipped, or might be shown brighter than 235 if the display
has head room.

Most computers monitors interpret 0 as black and 255 as white, so most
PCs expand the range 16-235 onto 0 to 255. If you drive a TV via HDMI
like that you'll get too much contrast and you'll lose some of the
darkest and lightest greys.

> - Where are the settings for nvidia and myth?  What are the defaults?

I don't know about the nvidia settings, but in myth, when using vdpau,
you can add the filter vdpaustudio in the render setup to make the
values 16-235 be mapped through unchanged.

> - What do most TVs do?

I believe most TVs expect studio levels on HDMI and full range on VGA.

> - How does this relate to YUV?

You don't have to worry about it for YUV.

Paul.