AVS HD 709 - Blu-ray & MP4 Calibration - Page 57

pigsworthy - For simplicity the most widely applicable response is in line with what PlasmaPZ80U had to say. The rest of this is just if you want further details.

A complication with black levels is that there are two standards for how black can be carried over HDMI. Either computer levels (full) are used so that black is at digital 0, or video levels (limited) are used so that black is at 16. Ideally the PS3 should convert everything to one standard so that video, images, and games are all being sent with black at the same level. If that is the case, then the brightness setting for video would also apply to images or games.

When you say you can see all the bars:
- Did you mean that you can see 1-25 if you turn up brightness? (not expected for RGB full)
- Or did you mean that you can see 17-25? (as described for setting brightness)
- Or is this maybe a mistake and you meant you can't see any of the bars? (brightness too low)

If the device is really outputting an RGB full range then it would typically be expected that the video would be remapped, so 1-16 would never be able to flash.

An issue with looking at a saved image is that some other setting could come into play that doesn't apply to video. For example http://www.avforums.com/forums/ps3-m...ml#post7245645 mentions that it's possible to change how images are displayed on a PS3. Ideally black would always be the same level regardless of the source, but that might not necessarily be the case.

Attached is an image that shows levels 0-25. Ideally black in the image (the background - 0) would be the same shade as black in the video (16).

 

Image-Black.zip 33.5126953125k . file

Not all displays will be able to clip at white. Even if they could it might not be recommended, because gamma might not be linear all the way to clipping. The described behavior seems normal for the Sony digital displays I've messed with.

From time to time there have been issues reported with sendspace, but the site was working when I tried. Personally if I was having the issue I might try downloading with a different browser, or else use a downloader like FlashGet or Orbit.

Generally this is to be expected, because you're using a computer.

COMPUTER AND VIDEO LEVELS
Computers and video use different ranges for black to white. With computer levels black is expected at 0 and white at 255, and sometimes computer levels are called Full or 0-255. On the other hand with video black is at 16 and white at 235, video also allows for 1-15 below black and 236-254 above white information that isn't necessarily expected to be displayed, and sometimes video levels are called Limited or 16-235. Blu-ray or DVD use video levels, so the Black Clipping Pattern shows levels from 1-25 with 16 being black.

By default most computers will decode video and expand it to match the Full range, so 16 from the video goes to 0 and 235 ends up at 255 and the information outside the 16-235 range is lost. What this means for the Black Clipping Pattern is that 17-25 are the only bars that are able to flash if video is expanded to computer levels. Even if video is expanded to computer levels the Black Clipping Pattern can still be used to set brightness on the TV, just set brightness to the lowest setting where the bar marked 17 just barely flashes.


If 17-25 flash on the Black Clipping pattern, you can set the brightness control on the display. One complication can be that by default most TVs expect a Limited or video input, rather than a computer input. If you are sending computer levels to your TV you might need to change a setting on the display to expect a Full range. At least that's how my Sony works, by default it expects a video input and it's best to set the TV to Full if the input uses computer levels.

In the ATI control panel the Avivo Video area is generally the place that controls video expansion. There is another set of brightness and contrast controls in the ATI panel under the "color" heading, but I would suggest leaving those controls at their default settings. On my card if I set the Avivo Video brightness to 16 and the Avivo Video contrast to 86 then the whole video range seems to be passed to the TV and Limited can be used at the display. I've read that FFdshow can also be used in the same way to retain the whole Limited range in a computer output, but the complication with either option is that then black for video doesn't match black for general computer use. On the other hand if you leave the Avivo Video brightness at 0 while setting the Avivo Video contrast to the high 90s it's possible to retain some above white from the video (CRT appears to display some above white), while leaving black at the same level for video and computer use.

Anyway I just tried to touch on a few main points:
- Video and computers use different ranges for black and white
- By default computers generally expand video levels to computer levels, which cuts off the 1-15 information shown on the Black Clipping Pattern
- You may need to set the display to expect a Full output from a computer
- There may be different ways for how you can deal with how your computer outputs video if you wish to change the default behavior

Today I uploaded a few minor revisions to correct some items reported from the v1.3 release. Since this update only includes minor changes, the documentation still reads v1.3 and merely the download files have changed as noted below.

1) HDMV and PATCHED versions were modified to correct for the end of section chapter skipping issue reported in http://www.avsforum.com/avs-vb/showt...0#post16741740 Now for all sections in the HDMV and PATCHED versions, when you reach the end of the section a chapter skip should return to the first chapter.
2) PDFs were modified to correct for the spelling mistake reported in http://www.avsforum.com/avs-vb/showt...3#post16736783
3) No changes were made to files for the v1.3 AVCHD, HD DVD, and MP4 versions.


NOTES FOR PRIOR RELEASES:
v1.3 Update Notes (5/24/09)
AVCHD v1.2b Revision (1/12/09)
v1.2 Release Notes (1/11/09)
AVS HD 709 v1.0 Update (11/1/08)
Release Candidate 1 (2/12/08)

Filters won't help with grayscale adjustments. Generally you need some sort of a reference for gray, such as a meter or gray cards and a neutral light.

On the SXRD TVs the White Balance area is grayscale. There is also a gamma setting that when not off will raise the light output for the middle range, effectively lowering the average gamma. I would generally suggest leaving the gamma and black corrector items set to off, based on how they change on-screen gamma.