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  #1  
Old 05-23-2016, 04:06 AM
Outland Outland is offline
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Early DVD Player Black Level

I've noticed that the Sony DVP-S7000, a reference level player with very good reviews from the time it was released, has a very strange issue.

As soon as the player turns on, the black level changes. Meaning, the lowest black the player outputs, even at the idle screen, is more gray. No other video equipment I have, including VCRs etc., does that.

Using any other DVD player gives a significantly better picture in my view, because the blacks are no longer washed out.

The S7000 is supposed to be one of the few players that can output blacker than black on test strips. Does that mean that the 'black' is in fact a few steps above 'true' black, meaning the black seen on a calibrated display is indeed the black on the disc and the other players just chop the 'true black' off if the disc calls for it? Or is the player just outputting a higher black level for some reason.
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Old 05-23-2016, 09:07 AM
Chip Chester Chip Chester is offline
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Digital equipment that has to interface with the analog world needs to support two different black levels. In analog, "black" is 7.5 IRE, which is sometimes referred to as setup. This has to do with the particulars of an NTSC signal. Digital gear has 0 IRE for black. There might be a menu adjustment available for this, it might switch based on analog or digital signal source (if that's supported on your machine) or it might not be adjustable by the user. Machines made when both systems were commonplace had to make some compromises.

If you can get access to a service manual, it will probably show what the design intent is, and outline adjustment procedures. You'll need a waveform monitor for this, and a vectorscope for color adjustments. If you choose digital/computer based options for these, using an interface, keep in mind that the particulars of that system may influence the accuracy of any measurements you make on the player.

Chip

Last edited by Chip Chester; 05-23-2016 at 09:11 AM.
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  #3  
Old 05-25-2016, 01:03 PM
Outland Outland is offline
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Surely other DVD players are also digital. It is only this Sony DVP-S7000 that has this raised black level for some reason. It is like the player is incapable of outputting the black every other device can.

A good explanation of the issue is that if one were to use a calibration disc, the resulting calibration would only be valid for this player, unlike if the disc was used on another player where the calibration would be valid for any other source.

I would just say it's a bad player, but this is a reference level player that has gotten excellent reviews for its picture quality (and black level!).

The connection is simple composite to a 20" Panasonic tube TV. The component and S-video outputs exhibit the same behavior. The player does not seem to have adjustable black level (though some online sources claim it does). The only way to counteract this is to lower the brightness on the TV to make the black become actual black just for this player.

The review I'm referring to: http://hometheaterhifi.com/volume_7_...r-11-2000.html.

EDIT: Interestingly, the DVD player that to my eyes has good black level has different numbers for black in the corresponding review: http://hometheaterhifi.com/volume_8_...er-3-2001.html. I don't know how to make sense of these numbers. Why is there a difference? To my eyes the PS2 has the correct black level. The review mentions "setup" like you do, so I assume you and they are talking about the same thing.

EDIT 2: The review says:

Quote:
There is no setup on the outputs, and there is no way to add it. If you calibrate your TV based on the PS2, then TV broadcasts will appear washed out because you have brightness set higher than it should be. If you have configured your TV based on another DVD player, then the blacks will be clipped and you will lose all shadow detail when you look at the PS 2.
But this is the exact opposite of what I see. Everything else, even the idle screen of a VCR has black as black, tapes have good black, LDs routed through the VCR have good blacks, and the PS2 has good black. The S7000, from the moment it turns on, ramps up the black level. This change from the VCR idle black to the S7000's idle black can be seen. What am I missing? The only logical conclusion I can make is that the S7000 is the only equipment calibrated for 7.5 IRE in my setup, and that the VCR outputs VHS and input blacks as 0 IRE for some reason.

If I lower the brightness to what the S7000 wants, tapes lose significant shadow detail and the picture becomes very dark.

Last edited by Outland; 05-25-2016 at 01:17 PM.
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  #4  
Old 05-25-2016, 07:42 PM
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All NTSC video pictures *should* include setup, that is, black=7.5 IRE and white = 100 IRE. The VCR idle screen may not include setup because the idle screen generator may be too simple and just make black as 0 IRE. If the black on the idle screen gets cut off, who cares - there is no detail in that area, and it reproduces as black anyway.
But- actual picture material should have setup of 7.5 IRE.

The thought that briefly passed through my mind was "is there some mixup of PAL specs and NTSC in the gear?" PAL used setup = zero.

Setup was one of the worst ideas of the original NTSC, put in there to prevent circuits from accidentally clipping lowlights. The second NTSC should have thrown it out rather than just tightening the tolerances. The result was that in most analog cable systems it was misadjusted and varied annoyingly from channel to channel. It was identified as one of the major variants in image quality by industry groups and a campaign was undertaken to at least get the broadcast stations more uniform.

Hard to say what's going on with your gear, but if you are using only analog outputs (no HDMI or etc. between devices), they should all have setup. Given the mess with setup over the years, they may just all be wrong.
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Old 05-25-2016, 07:49 PM
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It just struck me that you wrote '20" Panasonic tube TV.'

What evidence do you have that this TV clamps black to the back porch (or at all)? If it's setting levels from sync tips, all bets are off.
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Old 05-25-2016, 08:23 PM
Chip Chester Chip Chester is offline
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Chip wrote: "You'll need a waveform monitor for this..." Or a scope.
Likely the only way to know for sure what's going on.
And no guarantee the player is operating as designed, either.

Chip
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Old 05-26-2016, 12:38 AM
Outland Outland is offline
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Quote:
Originally Posted by old_tv_nut View Post
It just struck me that you wrote '20" Panasonic tube TV.'

What evidence do you have that this TV clamps black to the back porch (or at all)? If it's setting levels from sync tips, all bets are off.
How would I know? It's a 1994 stereo Panasonic CT-20S2S. It shares its tube with some higher-end models and is connected to a Panasonic PV-4060 VCR by RF, which is the only input it has. The DVD player is routed through the VCR. Why this VCR isn't affected by Macrovision, I have no idea. However, this phenomenon occurs on high-quality tubes as well with S-video, component etc with this player.

I think you've cracked it old_tv_nut, though. It appears I've calibrated the TV to 0 IRE, which is why the PS2's output looks good to me (which has 0 IRE as black, according to the review I linked). It makes sense that the S7000's 7.5 IRE looks gray.

Coincidentally, the VCR's idle screen happens to arbitrarily be 0 IRE. I don't watch tapes too often, and in fact the blacks are a little gray on tapes, but I attributed this to the inherent limitations of the VHS format.

So the solution would be to have two calibrations for brightness, one for 0 IRE and one for 7.5 IRE.

Thanks all.
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Old 05-26-2016, 11:33 AM
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This makes sense now that you note the tape blacks are gray.

I got off the track when you said 20 inch tube set. This must be a solid state set with CRT. It likely has decent DC restoration, or you would be noticing the blacks drift up and down due to variations in picture content.
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  #9  
Old 05-27-2016, 06:36 AM
Outland Outland is offline
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Quote:
Originally Posted by old_tv_nut View Post
This makes sense now that you note the tape blacks are gray.

I got off the track when you said 20 inch tube set. This must be a solid state set with CRT. It likely has decent DC restoration, or you would be noticing the blacks drift up and down due to variations in picture content.
Oh, I meant tube as in CRT, not tube as in vacuum tubes. Yeah, the blacks don't drift much.

Some more interesting info about setup is that in Japan black is indeed 0 IRE (since 1985), even though they have NTSC. I assume this is why the PS2, a system designed primarily for games, wasn't recalibrated to 7.5 for the American market. Why setup was invented, I'm not really sure. It doesn't seem like it does much if at all.
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Old 09-13-2016, 01:31 PM
Damnation Damnation is offline
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Sorry to dig up an old thread, but I have a couple 7000s and have noticed this "bright" black screen upon first turning on the player on my 27" Panasonic CRT via Component. Although I actually see the same thing with my Motorola cable box via S-Video when the box is (supposedly) turned off.

When the 7000 gets to the DVD content I don't see this phenomenon. The black bars on widescreen DVDs always blend properly into the surrounding darkness when watching at night. This player is indeed set to 7.5 IRE with no menu option to switch between 7.5 and 0 like some players. It passes "blacker-than-black" info unlike other players, even Sony's DVP-S7700 successor. I have a 7700 too and find the 7000's image quality better, shadow detail is definitely improved. The 7000 also doesn't have the chroma bug unlike the 7700 (not as noticeable as some players though). The 7700's picture might be a little sharper, but this is probably just edge enhancement "baked" into the video processing. The 7000 has a few picture adjustments (Contrast, Brightness, Color, Sharpness) that the 7700 totally got rid off.

One thing I've noticed with the Pioneers I have is that when set to 7.5 IRE, the black level always looks far too inky. Even with their DV-59AVi, often regarded as one of their best DVD players with regard to picture quality.

Last edited by Damnation; 09-13-2016 at 01:40 PM.
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Old 09-17-2016, 11:50 PM
Outland Outland is offline
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Indeed, the 7000 looks great. My problem earlier was that I had the TV calibrated to 0 IRE, and the player outputs 7.5. I don't know what that startup 'flash' is, perhaps some kind of internal calibration.
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Old 09-18-2016, 01:25 PM
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Quote:
Originally Posted by Outland View Post
...Why setup was invented, I'm not really sure. It doesn't seem like it does much if at all.
There were a couple of things added to NTSC standards that turned out to be unneccesary and eventually a detriment.

Setup was one. It was intended to prevent clipping of lowlights by inaccurate black level clamps. Professional gear quickly migrated to accurate back-porch clamping, and TV sets used none at all at first. The setup level was inherently a problem in accurate setting because there is no natural reference for it in a video signal, as there is for zero %. It really got bad when cable TV came in, because now there were thousands of video proc amps in cable systems, each with a different error in setup. As receivers began to be designed with better DC restoration, they just passsed through the errors. In the 70's the TV makers and broadcasters mounted a campaign to get all the broadcasters in a given market to monitor their setup and see that a match was maintained. The big cable operators also participated, but of course it was much more difficult for them to keep all those proc amps under control. The industry made a mistake by not petitioning the FCC in the 1950s to change setup to zero. The adoption of the color standard would have been a great time to do it.

Another area of unnecessary NTSC signal features was the sync equalizing pulses. The idea was to send H sync pulses at twice normal rate during vertical blanking, so the vertical sync separators in receivers would not get any horizontal rate energy, which would cause line pairing (poor interlace) by triggering vertical retrace on whole lines only instead of half lines (there are 262.5 lines per field, for 525 lines per frame). In fact, vertical serrations at twice horizontal rate would have been sufficient, and the main reason for poor interlace in receivers was all the horizontal sweep current running around the chassis and getting into the V sync circuit. The equalizing pulses were specified on the idea that H sync would be edge triggered on the leading edge of horizontal pulses or equalizing pulses- a really bad idea for noisy over-the air signals. All receivers used RC low pass filtering of the H sync to reduce noise, resulting in H sync being related more to the center of the H sync and equalizing pulses. The serrations in the wide V sync pulse were also timed based on edge detection for horizontal. The result was that all receivers had a slight pull of horizontal phase toward one side during vertical retrace. Fortunately, this was minor and not a real problem, but it caused Motorola to include an explanatory note in their data sheet for TV sync chips, since engineers, by the 70s, didn't know about this NTSC quirk, and would think the chip was at fault. The NTSC spec included both pre- and post- equalizing pulses (before and after the V sync), which is mathematically correct if you build a circuit that looks at the whole interval to determine the position of V sync. But, of course, the simple V integrators in TVs (until digital countdown ICs were implemented) had no such memory, and the post equalizing pulses were a waste, as they could only extremely weakly affect the following V sync a whole field later.
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  #13  
Old 10-02-2016, 05:39 AM
Outland Outland is offline
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Very interesting information. Thanks for sharing.
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