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View Full Version : Totally anal & pointless format rant



SCS
04-09-2004, 08:10 PM
Discovered this while playing back a DVD I authored using VT footage...

Put the SMPTE bars still from the Patterns folder on a TED timeline.

On VT-Vision (if you crank up the brightness), VT-Scope and any external monitor/scope you have, the lower right hand portion of the pattern shows both the +3% of 7.5 IRE black bar & -3% of 7.5 IRE black bar.

Now, render clips from the timeline in the following formats:
RTV, AVI_UYVY, AVI_YUV2, AVI_BGR32 & AVI_BGR24.

If you place the rendered clips back on the timeline, the RTV, AVI_UYVY & AVI_YUV2 look just like the original clip (both monitors and scopes).

However, the AVI_BGR32 & AVI_BGR24 are both missing the -3% of 7.5 IRE black bar - this means some loss of grey scale information. While this the spec for NTSC broadcast, it is a (minor) limitation in the non-broadcast Computer/RGB/digital media world (particularly if you are using Alpha information).

In any case, bring all those clips into another program (Premiere, After Effects, Media Player etc.) and you can't see the -3% of 7.5 IRE black bar in any of them! It seems to only display correctly in VT-Vision or an external monitor.

I know I could reset the 7.5 preference in TED, but that makes the -3% of 7.5 IRE black bar go below zero IRE.

--end rant

ScorpioProd
04-09-2004, 10:04 PM
This is a result of all YUV values not being able to be mapped to RGB.

Rich Deustachio
04-09-2004, 10:45 PM
You probably already know this but it is a help in setting up using color bars.

ColorBars (http://www.videouniversity.com/tvbars2.htm)

ScorpioProd
04-10-2004, 12:51 AM
Nice article. I remember how the VT[2] manual had some mistakes in the section on using test signals and the waveform monitor/vectorscope... It was quite amusing. ;)