[Tig] DVD players and 7.5 IRE setup

glenn chan glennchan
Tue Apr 18 08:51:23 BST 2006


--
Thanks to oktobor for supporting the TIG
--
A question:
Do the vast majority DVD players sold in North American markets (including
ones from China) correctly convert digital black level (Y'=16) to 7.5 IRE?
And white level (Y'=235) to 100 IRE?

I used to assume that this was true... but now it seems that I am wrong.
Someone pointed me towards the following thread, where it seems that some
DVD player/recorders are all over the place in regards to proper levels
conversion (i.e. 0 IRE instead of 7.5 IRE).
http://forum.videohelp.com/viewtopic.php?t=259098&postdays=0&postorder=asc&start=0
*Disclaimer:  There is lots of inaccurate information in that thread!

2- While I'm at it, let me double-check whether the following statements are
correct:

A- There is a lot of inaccurate and confusing information about 7.5 IRE on
the internet.

B- Proper levels:
For non-Japanese NTSC (i.e. North America), analog black level should be at
7.5 IRE.
For analog PAL, analog NTSC (Japan only), analog black level should be at 0
IRE.
For 8-bit digital video formats (i.e. DV, MPEG2), video levels are stored in
Y'CbCr form.  Y'=16 is black level, Y'=235 is white level.  Doesn't matter
if its PAL or NTSC.
IRE is an analog unit and has not place when discussing digital video
levels.
When processing digital video, either the studioRGB color space (black level
at 16, white at 235) or the computer RGB color space (black at 0, white at
255) may be in use.

C- Most DV devices in the North American market with improperly convert
digital black level to 0 IRE instead of 7.5 IRE.  It's evil.

D- Some DV cameras (i.e. PD170, DVX100) have a 7.5% setup settings that adds
FAKE digital setup.  It will record improper elevated digital levels, which
will give correct analog levels- but only when played back on devices that
fall under C.  It's evil.

E- Vectorscopes and waveform monitors in many NLEs are confusing and not
very accurate.
FCP:  Clips values under digital black level (i.e. the color bars has the
right PLUGE bars, but this doesn't display correctly on the WFM).  Digital
black level at "0".  Only scans the title safe area.  Gamma 'conversion'
when importing/exporting computer RGB graphics.
Vegas:  Levels depend on video scopes setting hidden in a menu.  You can
only figure out the proper levels by looking in that menu (ignoring the
histogram, which is sometimes not useful in this situation).  I believe
Color Finesse 1 may be like this.
Yes, also evil.


Glenn
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