IRE Help! Still Confused.....

[hrlslcbr]

@gadgetguy: You can view the levels with avisynth.

Just write: histogram() at the bottom of your script and you'll get a waveform monitor showing the maximum and minimum values for each frame.
You can try histogram("levels") too. If there's something in the waveform monitor touching the coloured areas to the sides, then the levels are out of the 16-235 standard.
Hope this helps.

Okay I tried this myself. I am using captured DV from Canopus ADVC, and opened the script up into VirtualDub, and got the histogram on the side. Unfortunately, it doesn't seem accurate. I used a video clip with blown-out whites, up to 255. The graph kept all whites at maximum of 235. Everything is automatically compressed down into 16-235 range. Nothing ever goes outside this range. Why is that? The "colortools" plugin that has it's own histogram, does the same thing.

How did you open the file in Avisynth? It could be your DV decoder that's compressing the levels because I do get accurate results.

[gadgetguy]

Keep in mind that my screenshot pictures have been reduced in size and compressed to jpeg so I'm not sure that an analysis of the pictures will give us meaningful results.
In my screen shots it's kind of hard to see, but the Avisynth histogram has yellowish shading from 0 to 16 and from 235 to 255. Before adjustments the black bars at the top and bottom are well above the "yellow" and the near whites in the main part of the screen are reaching into the yellow. After the adjustment the blacks are at the edge of the "yellow" and the whites are just shy of the upper "yellow".

[Wile_E]

How did you open the file in Avisynth? It could be your DV decoder that's compressing the levels because I do get accurate results.

I was using Panasonic DV codec. I tried Canopus codec, and now levels show correctly when using histogram(). Thanks for your advice. If I use the "color tools" plugin, it still doesn't show correctly. Everything is clamped down inbetween 16-235. This just isn't worth the trouble anymore. I need a tool I can depend on, as I want my captures done right the first time. That histogram is very vague, and hard to see the boundries. Looks like Sony Vegas is the only tool available with accurate histogram. I suppose I'll just have to buy it, if I have no other choice.

[hrlslcbr]

I was using Panasonic DV codec. I tried Canopus codec, and now levels show correctly when using histogram(). Thanks for your advice. If I use the "color tools" plugin, it still doesn't show correctly. Everything is clamped down inbetween 16-235. This just isn't worth the trouble anymore. I need a tool I can depend on, as I want my captures done right the first time. That histogram is very vague, and hard to see the boundries. Looks like Sony Vegas is the only tool available with accurate histogram. I suppose I'll just have to buy it, if I have no other choice.

I want that Vegas histogram too, but I just need to see if my video files are 'near' the 16-235 levels or if they are out of range. I discovered that the Nintendo GameCube outputs black at 0 IRE thanks to that avisynth histogram.
The Panasonic DV codec outputs to RGB only, so it must have 'expanded' the levels to 0-255.

[edDV]

I was using Panasonic DV codec. I tried Canopus codec, and now levels show correctly when using histogram(). Thanks for your advice. If I use the "color tools" plugin, it still doesn't show correctly. Everything is clamped down inbetween 16-235. This just isn't worth the trouble anymore. I need a tool I can depend on, as I want my captures done right the first time. That histogram is very vague, and hard to see the boundries. Looks like Sony Vegas is the only tool available with accurate histogram. I suppose I'll just have to buy it, if I have no other choice.

I want that Vegas histogram too, but I just need to see if my video files are 'near' the 16-235 levels or if they are out of range. I discovered that the Nintendo GameCube outputs black at 0 IRE thanks to that avisynth histogram.
The Panasonic DV codec outputs to RGB only, so it must have 'expanded' the levels to 0-255.

There is nothing unique to Vegas for a SMPTE/EBU standard set of waveform monitor and vectorscope monitors. This is a standard set of pro monitoring tools. You will find the hardware versions in all TV studio and transmission facilities and software versions are rapidly becoming commom in prosumer up NLE systems. You will find WFM/VS in Adobe Premiere Pro, Apple FCP, AVID DV Xpress, Sony Vegas and others.

Ref:
The waveform monitor is used for luminance and chroma levels vs time, The vector scope measures chroma gain vs phase.

The best source for TV test and measurement application notes is Tektronix.

They have all the white papers and guides you could imagine
http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/applications/vi...et=application
http://www.tek.com/Measurement/applications/video/analog_video.html

Understand Analog Measurements first. Capture is the most critical measurement point.
http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes/NTSC_...Set=television
http://www.tek.com/Measurement/App_Notes/25_7049/eng/section1.pdf

[hrlslcbr]

...This is a standard set of pro monitoring tools...

Yep, but Vegas might (and possibly is) much cheaper than any 'pro monitoring tool'. Anyway, I'm happy with the avisynth histogram, as I don't need much more precision than that.

[edDV]

...This is a standard set of pro monitoring tools...

Yep, but Vegas might (and possibly is) much cheaper than any 'pro monitoring tool'. Anyway, I'm happy with the avisynth histogram, as I don't need much more precision than that.

Unfortunately, the consumer version of Vegas lacks the video monitors. I hope these get added to the freeware-shareware-consumer products but there may be patent royalty issues.

[slacker]

I think I've been posting on the wrong thread!
For whatever it's worth!

When I encode the SMPTE NTSC test pattern and play it on my TV it is ALMOST dead right on, my Aquos requiring only -2 black level clicks which is not much at all. The Panasonic ES30VS dvd recorder is setup in its default configuration, which also corresponds to zorankarapancev's thread on the Panasonic black level setups. That would be...

input level = darker
composite & SVideo output level = lighter
component video output level = normal

So far everything is telling me that my Canon camcorder may be correcting during pass thru or something to that effect. And, if so, I won't have to correct my IRE levels post-capture.

Still playing wait and see until I check with Vegas' readings.

There seems to be three Sony VMS filters which touch on this thread's topic...

I believe these are implemented the same in Sony Vegas, but am not altogether sure.

Broadcast Colors, one template is called "Conservative - 7.5 Setup"
Color Corrector, one template is called "Computer RGB to Studio RGB"
Levels, one template is called "Studio RGB to Computer RGB"; this filter is cited above for adjusting IRE black levels.

All three seem to overlap in function although I have no technical knowledge of any of these other than what I have gathered from this web site.

[marksk918]

so, if i use the levels effect in adobe premiere 6.5, for the rgb channels, i'll set the black input level to 32 and the black output level to 16, the white input level to 255 and the white output level to 235. is that right or am i still confused?

Sounds right, I'll try it on my Premiere 6.5 (different computer) when I get a chance. I wish 6.5 had the scopes.

i've been using the above settings in premiere for some time. i'm starting to use avisynth with the convolution 3d filter. right now i'm adjusting my levels and editing out commercials in premiere, exporting the avi and then using an avisynth script with the filter and encoding in tmpgenc. i'd like to cut out the premiere step but have been unable to figure out the correct syntax to use for the levels feature in avisynth. can someone please point me in the right direction?

also, if i'm using avisynth's trim command to remove the commercials, how can i export the audio? i can't get a wav output from tmpgenc and don't want compressed audio.

thanks!