Correct Black Levels

[MasterOfPuppets]

In my pursuit to capture some NTSC-J tapes to my computer, I've come to believe that my VCR automatically fixes the black levels on the tapes. This being because while I was starting a tape the image suddenly became slightly brighter. Now, I might be wrong and it's not, but here's a file that I captured in regular NTSC, not J. Could someone tell me if the black levels are correct? If so, the VCR must be fixing the colors for NTSC.

http://www.mediafire.com/?nwmfmnmjbmn

Thanks!

[jagabo]

Assuming the black background in the opening shot is supposed to be black -- yes the black level is correct. You really need to look at a variety of shots to be sure. The peak brightness is pretty low. I think the brightest spot I saw only had Y at about 180. Peaks should be around 235.

[edDV]

Ditto Jagabo.

Black is either correct or crushed. I suspect it is being crushed by your capture card* to 7.5 IRE (digital16). You can see original blanking as the dot below the zero on the waveform monitor and also on the right side. NTSC-J should have black at blanking level. I suspect your card is crushing 0-15 digital levels to 16. Compare a direct analog VCR playback to a CRT TV and compare to the digital copy. Is low gray shadow detail being lost?

White is low for the clip provided. You need to search the tape for a clip with both black and peak white. Not all video goes all the way to full 235 white. It is a director's decision. In the broadcast world they put a representative color bar on the tape header to identify black and peak white per the directors intention. The actual program might lack a peak white or a full black. The playback or dub technician just sets transmission levels to the color bar.

Also, your audio levels show too hot and look clipped.



* or it could be your VCR altering the black level if it has a TBC or other output processing.

[MasterOfPuppets]

I know the audio is messed up; I just did a quick capture test for the black levels. The program seems to record it too high. I'm still on the hunt for a good free (or trial period) capture program.

How can I tell if it's my VCR? It's a DMP-BD70V, so it is a new VCR.

Thanks for the info so far!

[jagabo]

If you don't have Vegas you can use AviSynth's Histogram() to view levels. You want the darkest areas to just touch the brown bar on the left and the brightest areas to just touch the brown bar on the right. A frame from your MPEG file:


The black level is correct (although, it's possible that there where darker bits that where crushed somewhere along the line) but the white level is too low (assuming that bright spot was supposed to be at full brightness -- in the sample that spot and the text a few frames later are the brightest objects).

[edDV]

...
How can I tell if it's my VCR? It's a DMP-BD70V, so it is a new VCR.

Interesting combo player. Ideally you would have an NTSC-J VHS calibration tape. I wish I had one of these for a weekend to test. From the specs it looks like the VCR is separate from the Blu-Ray player. That is unless they share analog output circuitry. Do the Blu-Ray/DVD player or SD card stills output on the composite (yellow) or S-Video outputs? If not the VHS player probably connects directly to composite out (no A/D, D/A).

Does the VHS playback show on the S-Video output or analog component output?

The specs do show that VHS output can be upscaled to HDMI. I'd test to see if the upscale shows up on analog component as well.

In the Blu-Ray player spec they show an interesting feature -- "* Variable Black Level (Setup): 0 and 7.5 IRE" Does this do anything to the composite, S-Video or analog component outputs during VHS playback? Does it affect HDMI VHS upscale black level?


http://www.world-import.com/Panasonic_DMP-BD70v_Region_Free_Blu_Ray_DVD_Player_with_VCR.htm

What sources do you have to feed test signals into the VHS recorder? Most Sony Digital8 and MiniDV camcorders export composite and S-Video at NTSC-J levels.

[MasterOfPuppets]

Thanks for the info on the graph, I never understood those. I'll test out the program.

That's interesting... They have recording on the list of features even though that model can't. Anyway.

There is no S-Video on the player, but Blu-ray, DVD and VHS can all be output through the composite, component and HDMI.

I tested the brightness and it does not seem to work on VHS (with analog connections at least). I set it to lighter and for a split second after I press play the screen is a lighter black and then switches to a darker one. If I select darker for the brightness, there is no switch in the black levels before play. Would it be possible for it to detect the colors of the tape during playback and adjust for it like I thought, or not? Also, interestingly enough, I selected 720p for component out (that's the highest my TV goes) and the black select didn't change anything, only on 480i(p?).

Should I try a capture with a traditional VCR and see if it fixes the levels? I already know that if I select NTSC it severely crushes the blacks, and with NTSC-J it looks fine. I like this VCR though because even through composite it cleans up the picture lot.

[jagabo]

IRE Setup only effects analog video.