Signal Processing on Sony HDTVs  

Just so we're all on the same page, here's the background:

DVI on Sony 2002 vs 2003
Vertical bar on Sonys when viewing 1080i
DRC modes on Sony sets
So SONY 4:3s only scan HD in their 16:9 area?

And here's the latest from the last link:

Montreal,

If there is any unnecessary processing/conversion being applied to 1080i on the pre-2003 Sonys, I'd definitely like to try to get to the bottom of it.

I tried setting HDPT=0, and I do see a noticeable difference in the 1080i picture. I really need to get a look at a service manual, so I have a better idea what's going on in these circuits, but so far here's what I've been able to discern just playing around in the service menu.

1) With HDPT=1 (the default setting), the PQ of 1080i looks very similar to 480p and 720p, in terms of it's sharpness and saturation. However with HDPT=0, 1080i looks a bit different than the other two signals. It seems softer, less yellow, and not as saturated on my TV. Perhaps not quite as edgy or punched up.

2) Setting HDPT=0 only seems to effect 1080i on my TV. 720p & 480p look the same regardless of whether HDPT is 0 or 1.

NOTE: In Post #277 where the bar fix is mentioned, it states rather explicitely to select the RF input on some TVs before changing HDPT. So perhaps it's not such a good idea to change this item while 1080i is actually being displayed on some TVs.

3) When HDPT=1 (the default setting), changing MID1/DPSW to 0 seems to disable the video signal for 480p, 720p and 1080i, turning the screen black,(but leaving the CRT itself on).

WARNING: Changing DPSW eliminates everything from the screen, including the service menu!!! So if you push the wrong button on the remote or write changes to memory while the screen is blank, you could have a VERY difficult time getting any image back on your TV screen!!!! This stuff is for advanced service menu users only! And until more is known about this setting, I would not recommend that anyone else change it from the factory default, unless you use extreme caution and know what you're doing.

4) However, when HDPT=0, changing MID1/DPSW from 0 to 1 seems to have no effect on 1080i. IOW, the "new" 1080i picture stays on, and looks the same as far as I can tell. However, 720p, and 480p still go black as before. Again, HDPT appears to effect 1080i, but not 720p or 480p.

5) When HDPT=0, none of the MID..... sizing and positioning adjustments I've been using have any effect on the "new" 1080i picture. Like everything else though, it is resizeable with the global sizing and positioning controls in 2170D-1 (VPOS, VSIZ) & 2170D-2 (HPOS, HSIZ).

6) Unlike most service menu items, it appears that HDPT does not need to be written to memory to take effect. It seems to stay at whatever value you last entered.

7) Irrespective of any of the above, 480p does look different than the interlaced modes when viewed close up. 480p has much more distinct dots/scanlines with spaces in between than the interlaced modes. So at least in terms of what's on the screen, it appears to be scanning differently.

8) With HDPT=0, the "new" softer 1080i picture on my 34XBR800 reminds me a little bit of the softer (but perhaps more precise?) character of the image on the 34XBR910. This is probably just wishful thinking on my part though. :)

So I guess, here's my question,.... just to kind of break this down. Do you think that switching HDPT to 0 could reroute 1080i so it bypasses some of the processing or conversion that's being applied to the other signals?

:D

I was one of the unbelievers regarding the different circuitry paths. However, if there is a difference, then it would be very cool if somethin like HDPT could be used as some sort of work-around. I'm not sure we can jump to that conclusion yet though. There are still alot of unanswered questions in all this.

Plus, we still do not know the significance of DPSW in all this.

DPSW is rather tricky BTW. If you leave it set with the picture turned off, and then press the wrong button on the remote, or write the new setting to memory you may have a heck of a time getting an image back on your TV!!!!! Because it eliminates everything from the screen, including the service menu.

So BE CAREFUL if you start playin around with this!!!!!!!!!!!!!!!

THIS STUFF IS NOT FOR THE NEWBIES.

:) Yes, I guess changing to a different video input, or using the memory recall feature on the remote should "erase" the last DPSW entry and get the picture back, provided it was not accidently write it to memory. :) Is that what you're referring to? Or have you perhaps tried the "SM reset"? I don't know anyone who's tried the latter for fear of possibly undoing factory tweaks. I've been tempted to give it a go myself though.

BTW, I think the "new" 1080i wth HDPT=0 looks a bit more natural on my TV. It may be my imagination but it seems to have more subtle shades of color. And as I was saying above, it appears to eliminate some of the yellowish tint I've noticed since "correcting" the color decoders and using the Samsung 931 player, as well as reducing some edginess. Not sure if it's safe to leave HDPT at this setting though.

Very interesting indeed. I'm definitely glad you brought this out. Actually I am (unfortunately) NOT seeing any change in 480p as a result of setting HDPT=0. It looks identical regardless of how HDPT is set. The same with 720p. Only 1080i seems to be effected by this item on my TV. I tried using some of the MID2 sizing controls on 480p after switching HDPT to 0 just to verify this, and they still work as before. So there appears to be no change to 480p.

480p does appear to scan progressively though, rather than being converted to an interlaced mode, as I mentioned above.

Perhaps there is a separate or add'l setting somewhere else which could force a 480p bypass as well. That seems consistent with what I'm seeing on the "new" 1080i, with HDPT=0.

I don't know about the 910, but NTN1's remarks re the upconversion of all signals to 1080i do not seem to jibe with what I'm seeing on my 34XBR800 screen. Again, 480p appears to scan progessively on my TV. I've been doin digital imaging alot of years, and I'm pretty sure I can distinguish the two close-up. Having one of the DVI players handy helps though, because you can easily switch between 480p and 1080i to see the difference.

However, if all you have is an analog 480i player, you can still see a difference between the interlaced and progressive modes. If you look at the screen close-up with a fairly static image, like the splash/menu screen on a DVD or the white level THX test pattern, and then switch between the different DRC de-interlacing options, you should be able to see the difference. Progressive and Cinemotion will have very distinct dots/scanlines, while the Interlaced mode will not. Interlaced will have a "smoother" appearance due to the offset of the alternating scans.

Perahps the TV is looking at the horizontal scanrate/sync (or whatever the correct term is) to distinguish between the different incoming signals. If memory serves, 480i=15.75kHz, while 480p=31.5kHz, and 540p/1080i=33.75kHz.

Eventually, I think the best way to handle all the different fomats on this current crop of 1080i hi-scan TVs may simply be to convert them all to 1080i via a HQ external STB and input that via DVI. The DVI players seem to demonstrate that this can be done pretty well, provided the video source is digital to begin with. If you don't have a DVI port on your TV, then going component 1080i from an external digital video hub could still be the next best thing.

I sympathize with your desire to see some more pure 480p in the meantime though. :)

I think you're probably correct, xrox.

[Without the HDPT bypass] 540p from my HTPC seems to be treated just like 1080i on my TV. I.e. the alternating 540-line scans are still offset. Since the horizontal scanrates on an incoming 540p and 1080i signal are the same, perhaps the TV may have trouble distinguishing between the two, and switching the screen to progressive scan for 540p [without the HDPT bypass].

960i probably works differently though since it's generated internally by the TV's DRC functions. So as you suggest above, the TV's DRC may be able to switch the 31.5kHz signal it sends to the CRT from progressive to interlaced to deliver either 480p or 960i on the screen.

Whether the 34XBR910 works the same way though, I really don't know for sure. I haven't looked at one with the same level of scrutiny as my 34XBR800.

I notice in Post #277 where the bar fix is mentioned, that it states very explicitely to select the RF input on the TV before changing HDPT. So perhaps it's not such a good idea to change this item while 1080i is actually being displayed on some TVs.

I'll get to your questions, montreal, but I just noticed something extremely weird today re 540p computer DVI input on my 34xbr800.

When HDPT=1, 540p scans interlaced, as though it were 1080i. No surprise there. However, when HDPT=0, 540p scans progressively! (with no jitter/flicker) on my TV, AND the signal type in the service menu is still registering as 1080i. Furthermore, DPSW does not disable the "new" progressive 540p.

So with the HDPT "bypass", these TV's seem to be smarter than I've given them credit for. I thought it would see all 33.75kHz signals the same and simply display them as interlaced 1080i. This is the way it seems to work when HDPT=1. But with HDPT=0, 540p scans progressively. So maybe the TV can sense something other than the horizontal scanrate to distinguish between an interlaced and progressive signal.... at least on a "bypassed" 33.75kHz signal.

To review:

HDPT=1
33.75kHz 1080i = interlaced scan
33.75kHz 540p = interlaced scan
And both 540p and 1080i can be disabled with DPSW=1

HDPT=0
33.75kHz 1080i = interlaced scan
33.75kHz 540p = progressive scan
And neither 540p nor 1080i can be disabled with DPSW=1

I also notice the same changes in PQ when switching HDPT from 1 to 0 with 540p as I did with 1080i. So I'm pretty sure that the HDPT "bypass" works for 540p as well, and it somehow preserves it's progressive scanning as well.

Regrettably, a 480p computer input seems to behave exactly the same as 480p from the DVD players. I.e. the HDPT "bypass" does not seem to work on it so far.

Another thing.... with the "HDPT bypass" enabled, I'm not getting the vertical phasing I used to see on 60Hz 540p signals anymore. So perhaps that is a product of the old MID/DRC processing as well.

Montreal you are da bomb! :)

Now if I could just figure out some way to scale this "new 540p" to better fit the screen.... ;)

Another interesting wrinkle....

While the "HDPT bypass" appears to have no effect on 480p from my DVD players or the Standard 720x480p HDTV mode from my computer, 848x480p does seem to be effected by it. It appears as though 848x480p may be upconverted by the TV to 540p. It registers as 1080i in the service menu, and seems to work the same as 960x540p with regard to the HDPT settings....

HDPT=1
848x480p = interlaced scan (1080i?)

HDPT=0
848x480p = progressive scan (540p?), no flicker, better PQ IMO.

Perhaps the greater horizontal resolution is what's kicking it into 540p upconversion. (?)

848x480p is still not as good as 960x540p though on my TV. So the upconversion is causing some jaggies, and so forth. Not bad though. The "new progressive 960x540p" may be the clearest computer image I've seen on my TV so far though. A little Clear Edge VM (velocity modulation) doesn't seem to hurt it too much either.

I'm not sure about that. On my TV, DPSW seems to disable all the normal "processed" signals, no matter what format they are. My suspiscion is that it may be disabling the circuit which converts all signals to your "1080.0001i". The HDPT bypass seems to work on my TV without changing the DPSW switch from the factory default. It's possibe that this may work differently on other TVs though, perhaps the 34XBR2's for example.

I'm sorry to keep postponing answering your quetsions, BTW, but I just can't get over the difference this HDPT option makes on 540p!!!! :D :D

All of the processing/enhancment jazz on the picture seems to be removed, and there's nothing left but a pristine progressive image. It is truly stunning to behold!!!

This is an amazing find, Montreal!!! If I could figure out a way to remove the overscan on this new picture, I think I could almost use this as a fulltime computer display!

Actually that's wrong. Because as I've stated repeatedly, even the normal "processed" 480p scans progressively. I don't think DPSW is necessarily discriminating between progressive and interlaced signals. It just seems to disable all the normal "processed" signals, but it leaves the "bypassed" signals intact... on my TV anyway. As I said though, I left DPSW alone, at the factory default of 0. The only change I've made in the service menu to enable th bypass on my TV is OP/HDPT=0.

I am about as convinced as I think I could ever be that in it's normal configuration (before the HDPT and "bar fixes"), that pre-2003 Sony's like mine are performing additional internal A/D->D/A conversion/processing on all signals including 1080i, to keep the picture quality/handling uniform. And that this add'l processing is destructive to the PQ.

On my TV, HDPT seems to allow 540p/1080i to bypass this, revealing a more pure un-sweetened/un-enhanced image. Other folks mileage may vary though.

It's possible that changes like this could have other consequences (possibly unpleasant ones) either up or downstream from the HDPT switch, perhaps depending on variations in the TV's hardware. So anyone considering making this change should be aware that there may be some risks involved in doing it without technical supervision from Sony. 34XBR2 users may want to be particularly cognizant of this.

FWIW, people who've had a successful "bar fix" by a Sony tech are probably already reaping the benefits of this "bypass" on 1080i/540p.

(Mon plaisir. :) )

The progressive may be part of it. But I think the 33.75kHz picture just looks better defined overall with the HDPT bypass. (And it seems to work better with VM.)

I noticed some of these differences with 1080i on the DVI player too. The difference is even more apparent with the sharp graphics of a computer input though, and I'm not surprised now why my eyes have been strained by the older image. The Trinitron grille still gives me some problems, but with the "new" DVI 540p, the picture is much more pleasing to look at.

We're getting into nuances here now, but one subtle difference between 540p and 1080i is that the progressive scan of 540p makes a more well-defined "dot" on my TV. The better-defined scanlines of the progressive scan may counter-balance the strong vertical lines in the Trinitron grille a little better than 1080i. However, I have the feeling that users running a computer input at full interlaced 1080i would be very pleased with the result as well, due to the diminished "processing" alone.

I haven't forgotten about your earlier questions, BTW. I'll try get back to those in a moment.

I think the RF input is the VHF/UHF coaxial input. It's indicated simply as "TV" in the service menu on my TV. So it's not the same as Video 1. Video 1 is the first S-video/Composite input on my TV. Nope, initially I tried it on Video 7, the DVI input, so I could see what happened when I switched the DVI player to 480p, 720p and 1080i. I also tried switching it on the RF and Components inputs to and got the same result. It blanked the 480i/480p picture on all the inputs I tried. Understood. And that seems to jibe with results on my 34XBR800 as well. Most definitely. Changing DPSW on any of the normal "processed" signals blanks the entire screen, erasing everything, including the service menu's OSD. Hence my earlier warnings about this. Curious. I'm not sure you can conclude from this that DPSW is cutting off the picture at the CRT driver circuit though. The SM OSD may need to piggy-back on some kind of video "carrier wave" to be visible, which could originate much earlier in the TV's circuits, perhaps in or before the DRC or MID circuits. And perhaps this "carrier" is also cut off by DPSW well before the CRT driver.

And again, the "bypassed" 540p/1080i signals seem to be immune to the DPSW setting. They stay "on" regardless of how it's set on my TV... and they do carry the SM OSD as well. Not a clue on that one. Maybe the hardware bar patch works a bit differently on the 34XBR2 though, since it's a bit older. As you've pointed out a couple times, there seems to be a little variation in how the bar fix works from model to model.

I think I died and went to heaven. :)

The picture on my measly, flea-bitten, abused, open-itemed, direct-view Sony CRT now looks almost as good as a $5000 LCD or plasma. :)

I'm not worthy, Montreal. :)

... and Uzun I should add, since you weren't willing to let this issue go. And everyone else at AVS... for that matter. :)