TV screen ratio

[baward]

Hello,

Can anyone tell me where the function in altepg is for automatically changing the TV picture to display properly? It used to do this with no problem, but now I have to manually do it when for instance an old (4:3) movie comes on.

This used to happen automatically but I have managed to turn it off somewhere and I can't find it... The Freeview channel on the TV (as opposed to the TiVo channel) is still 'flipping' the picture appropriately.

To help me track down where the function lives, is it likely to be the TiVo itself or the TiVo's Freeview box settings? I hope I have been reasonably clear

Thanks.

[DX30]

My guess would be the TV is actually the most likely.

Try going to a TiVo menu such as "Now Playing" as this outputs a 4:3 picture. Does the TV automatically switch to have black bars at the sides? If not then it will be down to the TV settings.

If however the TiVo menu's do automatically change but 4:3 programmes don't then take a look at the Freeview box. Try pressing the TiVo AUX button to view the Freeview box directly. If the TV doesn't then automatically change then the Freeview box isn't outputting a 4:3 picture so look at that.

p.s. Some TV's let you choose how to handle 4:3 on a per input basis so you might find while it is set one way for the internal tuner it is another for the scart input.

[The Larch]

Interesting you say you're sure it used to work. After I reconfigured my parents' TiVo for altepg, I noticed that the switching wasn't working right, but I'm sure it had been when I installed the freeview box. But since I couldn't imagine any way that the altepg system might affect it, I thought I was imagining things.

In their case (on a Sony KV-28HX15U), I found a partial fix by disabling the 'Auto Format' setting in the 'Detail Set Up' menu, and manually setting the screen format to 4:3. When the TiVo sets the SCART widescreen signal, it switches to 16:9. When it doesn't, after a while it reverts to 4:3. The problem was that the telly was remembering the last format specified in line 23 WSS data, and reverted to that when the SCART widescreen signal wasn't there. I had to tell it not to do this, but to stick with what it was manually set to. It behaves a bit oddly sometimes, occasionally flips to 4:3 briefly during playback, and it doesn't handle other formats like 14:9, so it's not perfect.

As far as I can tell, SCART pin 8 switching works on the TiVo, but line 23 switching doesn't. TiVo obviously reads the line 23 data and asserts the SCART pin accordingly, but the line 23 data doesn't make it through to the telly. Unfortunately SCART switching is a lot more limited than the line 23 switching - in particular, in the absence of the SCART widescreen signal, the telly can't assume that it's a 4:3 picture, hence the need to manually set 4:3 when the signal isn't there.

I'd love to know if line 23 switching works for anyone else. It works fine on pass-through (on both the aux and vcr inputs), but not on recordings, or in live tv on the TiVo. If I flip between the aux input and live tv, the picture is offset a few lines upwards in live tv, so the line 23 info is going to either be on the wrong line, or cut off completely.

I said I didn't think that changing to altepg could have anything to do with it, but looking at http://en.wikipedia.org/wiki/Widescreen_signaling, PAL-M and NTSC signals have the data on lines 20 and 283 instead. I suspect that the TiVo is finding the line 23 data, and realigning the output so that it's on line 20, hence the slight vertical shift.

Is it at all possible that there's a mystery bit somewhere in the guide data that says that this source (or this channel), transmits line 23 data instead of line 20/283 data? That would explain things...

[DX30]

I'd love to know if line 23 switching works for anyone else.

I've just tried line 23 switching on my TV using a 3 wire composite connection and it works correctly for the TiVo replaying recordings, live TV, and aux bypass. I don't have a VCR so I didn't check that. FYI - it's a Panasonic TV and I was running the AltEPG image.

I did some beta testing for Topfield when they introduced Line23 switching and ISTR that Sony TV's were one of the problem makes. TV manufacturers differ in their interpretation of the Line23 spec. e.g. What happens if the Scart and Line23 disagree? What happens if the Line23 signal is removed?

If I flip between the aux input and live tv, the picture is offset a few lines upwards in live tv, so the line 23 info is going to either be on the wrong line, or cut off completely.

My TiVo has always had that offset but that isn't what determines line 23. The picture offset is determined by the timing of the vertical sync pulse relative to the start of the picture. Line 23 is determined by counting 23 horizontal sync pulses after the vertical sync pulse, not by guessing based on the time after the vertical sync.

Is it at all possible that there's a mystery bit somewhere in the guide data that says that this source (or this channel), transmits line 23 data instead of line 20/283 data? That would explain things...

I don't think so. If I set the stb to output a 4:3 center cutout then I get a 4:3 picture on replay etc. not one stretched to 16:9.

[The Larch]

I've just tried line 23 switching on my TV using a 3 wire composite connection and it works correctly for the TiVo replaying recordings, live TV, and aux bypass. I don't have a VCR so I didn't check that. FYI - it's a Panasonic TV and I was running the AltEPG image.

Thanks for checking this. So the line 23 data is definitely preserved by your TiVo. It ought to be the same on my parents' (although it's on the original software), so the difference is presumably that your telly picks up the line 23 data, and theirs doesn't, and presumably the OP's doesn't.

And so it doesn't seem like I've hijacked your thread, baward, what telly do you have, and does it have a similar setting?

I did some beta testing for Topfield when they introduced Line23 switching and ISTR that Sony TV's were one of the problem makes.

Are the results of those tests preserved anywhere on the web? I'd be interested to have a look. FWIW, as far as I can tell the Sony format switching works really well when picking up the line 23 data (changes quickly and correctly, doesn't stretch the picture unless you ask it to, etc.) and as well as can be expected for the SCART signal, which only gives a positive indication in one direction.

TV manufacturers differ in their interpretation of the Line23 spec.

Well, there's a surprise!

e.g. What happens if the Scart and Line23 disagree?

Well, I can't imagine a situation where the SCART would say widescreen and the line 23 data say 4:3, but my suspicion is that the SCART signal would have priority on the Sony. And they can't disagree the other way around, because there's no way for SCART signalling to positively assert that it's 4:3.

What happens if the Line23 signal is removed?

I assume you mean a situation where there's initially line 23 data present, and the telly has switched to that format, then all of a sudden there's no line 23 data at all. This appears to me to be the situation that's causing the problem... the TV can get the line 23 data from the STB, but not from the TiVo, and since they're on the same SCART input it sees it as the line 23 signal disappearing.

That's what the configuration option I mentioned relates to - you can set it to either remember the last line 23 format it saw (and therefore stick with that), or drop back to whatever aspect ratio you last manually set it to. (Of course, the manual doesn't actually explain what it does, but that appears to be the effect.) And it seems to wait a while before switching back, presumably in case the line 23 data is a bit patchy (as I imagine it can be on, for example, VCR playback). Either way, if the SCART widescreen signal is still there, it displays 16:9.

My TiVo has always had that offset but that isn't what determines line 23. The picture offset is determined by the timing of the vertical sync pulse relative to the start of the picture. Line 23 is determined by counting 23 horizontal sync pulses after the vertical sync pulse, not by guessing based on the time after the vertical sync.

Yep, agreed - I think we're at cross purposes. The lines are, by definition, numbered with reference to the vertical sync pulse. So surely, if the picture from the TiVo is offset upwards compared to the original signal, that implies that the picture data is occurring a few lines sooner after the vertical sync signal that it did originally.

Does the TiVo interpret and store the line 23 data when recording, and then reconstruct it on playback, or does it just record it as the left hand side of the first line of picture data? If the latter, the vertical shift will have moved it to the wrong line. I suspect that your Panasonic is happy to accept WSS data on a different line, while the Sony insists on it being on line 23, which would explain the difference in behaviour. Does that make sense?

Is it at all possible that there's a mystery bit somewhere in the guide data that says that this source (or this channel), transmits line 23 data instead of line 20/283 data? That would explain things...

I don't think so. If I set the stb to output a 4:3 center cutout then I get a 4:3 picture on replay etc. not one stretched to 16:9.

Hmm, not sure I follow your reasoning here, but I think I expressed myself badly in the first place. However, if you're sure the vertical offset has always been there, then obviously that's not an altepg difference. And perhaps I'm mistaken in thinking that it used to work. It's possible that I had toggled the 'Auto Format' setting at some point in between, and forgot about it.

That vertical offset is a bit puzzling though. Is it possible that it's a result of TiVo having originally been engineered for NTSC (where the picture data starts on lines 20 and 283), then (incompletely?) adapted for PAL (where it should start on lines 23 and 336).

Ah, just found this: http://archive.tivocommunity.com/tivo-vb/showthread.php?s=&threadid=77999, which relates to a similar vintage of Sony telly. I'll have to try out switching to PAL only when I have an opportunity, and see if it has any effect.

[DX30]

Are the results of those tests preserved anywhere on the web?

Not as far as I know, it was a closed beta.

Well, I can't imagine a situation where the SCART would say widescreen and the line 23 data say 4:3, but my suspicion is that the SCART signal would have priority on the Sony.

They tend to disagree, albeit briefly, every time the source changes between 16:9 and 4:3 and visa versa. Line 23 only occurs once per frame and the change seldom exactly co-incides with the voltage change on the scart. Different TV's react in different ways to the transition.

As far as I recall it is line 23 that should take priority over scart pin 8 - it is more versatile than scart and can do various letterboxing functions in addition to simply 4:3 / 16:9 switching.

There is a 3rd method of widescreen switching as part of scart smartlink specification that should take precedence over both scart pin 8 and line 23 but I have never seen anything that implements it.

And they can't disagree the other way around, because there's no way for SCART signalling to positively assert that it's 4:3.

Scart pin 8 is 12 volts for 4:3, 6 volts for 16:9.

I assume you mean a situation where there's initially line 23 data present, and the telly has switched to that format, then all of a sudden there's no line 23 data at all.

Yes, that is the situation. The expectation is a video signal without line 23 data is 4:3. If there was line 23 data saying the picture was 16:9 and that is then removed some TV's will quickly revert to 4:3. Some TV's however will stick at 16:9 until they see another line 23 signal telling them it is 4:3. The results during the beta was during 4:3 programmes some TV's would correctly switch to widescreen for advert breaks but not switch back to 4:3 when the programme resumed.

The lines are, by definition, numbered with reference to the vertical sync pulse. So surely, if the picture from the TiVo is offset upwards compared to the original signal, that implies that the picture data is occurring a few lines sooner after the vertical sync signal that it did originally.

No - what it means is the gap between the end of the vertical sync pulse and the horizontal sync pulse for first line is less. By changing the timing of the vertical sync relative to the lines in the picture you move it up or down.

Does the TiVo interpret and store the line 23 data when recording, and then reconstruct it on playback, or does it just record it as the left hand side of the first line of picture data?

The line 23 signal gets constructed at playback. The stb doesn't need to output line 23 at all. The TiVo can use the scart pin 8 input to tell if the recording is 4:3 and 16:9 and will still output a line 23 signal even if there wasn't one there originally.

If the latter, the vertical shift will have moved it to the wrong line. I suspect that your Panasonic is happy to accept WSS data on a different line, while the Sony insists on it being on line 23, which would explain the difference in behaviour. Does that make sense?

The Panasonic only uses line 23 for PAL. I think you are getting hung up on the vertical picture shift but as I've said this only indicates a timing change between vertical sync and the first horizontal line of the picture.

Hmm, not sure I follow your reasoning here

The point I was trying to make is for a given programme I can record it as either 4:3 or 16:9 by changing the stb settings. If the guide data specified the aspect ratio in some way then this wouldn't happen.

Ah, just found this: http://archive.tivocommunity.com/tivo-vb/showthread.php?s=&threadid=77999, which relates to a similar vintage of Sony telly. I'll have to try out switching to PAL only when I have an opportunity, and see if it has any effect.

Certainly worth a try.

[The Larch]

They tend to disagree, albeit briefly, every time the source changes between 16:9 and 4:3 and visa versa. Line 23 only occurs once per frame and the change seldom exactly co-incides with the voltage change on the scart. Different TV's react in different ways to the transition.

That makes sense, but at worst should only mean a slightly inelegant transition between formats. No bearing on the TiVo situation, anyway.

As far as I recall it is line 23 that should take priority over scart pin 8 - it is more versatile than scart and can do various letterboxing functions in addition to simply 4:3 / 16:9 switching.

Again, makes sense, although it won't matter (except perhaps during transitions), since if pin 8 says 16:9, line 23 will say 16:9 anamorphic, won't it?

And they can't disagree the other way around, because there's no way for SCART signalling to positively assert that it's 4:3.

Scart pin 8 is 12 volts for 4:3, 6 volts for 16:9.

Ah, but that's not quite right, is it? The 6V signal was an extension to the original SCART spec. It was originally just the signal for the source being active. If you see 12V on pin 8, you can't assume it's 4:3, since it might be a 16:9 picture from a source that doesn't support the 6V signal, so you shouldn't think of it as contradicting the line 23 data in that instance.

Yes, that is the situation. The expectation is a video signal without line 23 data is 4:3. If there was line 23 data saying the picture was 16:9 and that is then removed some TV's will quickly revert to 4:3. Some TV's however will stick at 16:9 until they see another line 23 signal telling them it is 4:3. The results during the beta was during 4:3 programmes some TV's would correctly switch to widescreen for advert breaks but not switch back to 4:3 when the programme resumed.

Hmm, anamorphic 16:9 pictures preceded the introduction of line 23 did they not, so it's dangerous to assume a lack of line 23 data definitely means 4:3. I can see why some manufacturers might have stuck to the conservative approach of not changing format if it wasn't sure what format to go to. And on my parents' Sony at least, there's a (badly documented) option to set the behaviour in this case. Presumably the fix was for the Topfield to insert line 23 data for any frames where it was missing.

No - what it means is the gap between the end of the vertical sync pulse and the horizontal sync pulse for first line is less. By changing the timing of the vertical sync relative to the lines in the picture you move it up or down.

I assume you mean the horizontal sync pulse for first picture line.

A modern PAL signal is going to comprise, AFAIK, five lines (lines 1-5) of vertical sync, followed by 17 lines (lines 6-22) of PDC, teletext, subtitles etc., then half(ish) a line of line 23 data plus 287.5 lines of odd field picture data (23-311), then more vertical sync and the even field. All lines other than those containing vertical sync will start with a horizontal sync pulse, and counting those pulses tells us what number the line is. And those pulses will be happening every 64us.

So the question is, how many horizontal sync pulses occur between the vertical sync pulse and the first line of picture a) on the original signal from the STB, and b) on the signal from the TiVo? If the time is different, the line number must be different. And if it's different for the first line of picture data, what about the line on which the line 23 data is present, which would normally be the same line?

The line 23 signal gets constructed at playback. The stb doesn't need to output line 23 at all. The TiVo can use the scart pin 8 input to tell if the recording is 4:3 and 16:9 and will still output a line 23 signal even if there wasn't one there originally.

Ah, OK, that's useful to know.

The Panasonic only uses line 23 for PAL. I think you are getting hung up on the vertical picture shift but as I've said this only indicates a timing change between vertical sync and the first horizontal line of the picture.

Fair enough, it could be unrelated, but that timing change must mean that the picture data, which on odd fields should start on the second half of line 23, starts on an earlier line. So if the line 23 data really is on line 23, it must be overlaying the picture data slightly (unless some of the original picture data is being discarded). Hmm, I wish I had a convenient way to actually view the signal...

And if that's nothing to do with it, there must be some other explanation why some tellies don't seem to see the line 23 data output by TiVo, when they do see the line 23 data output by the STB. Does TiVo output an unclean line 23 signal that they don't like? Not that it matters all that much, since it's not something we're going to be able to fix...

The point I was trying to make is for a given programme I can record it as either 4:3 or 16:9 by changing the stb settings. If the guide data specified the aspect ratio in some way then this wouldn't happen.

Ah, I see. I wasn't suggesting that the guide data gave the aspect ratio of the programme, but I realise I didn't express myself clearly. No matter, it doesn't seem to make sense in light of what you've said anyway.

[DX30]

After a bit of googling to refresh my memory -

The vertical shift has been talked about for at least ten years and may have been a workaround for some flashing green screen problems in software versions 1.5.0/1 , see

http://archive.tivocommunity.com/tivo-v ... adid=96282

Over the years several people have reported problems with some Sony TV's in relation to line 23 switching, not just with TiVo's but other equipment (e.g. Philips DVD Recorder). None seem to have got to the bottom of why they are incompatible.

http://archive2.tivocommunity.com/tivo- ... p?t=238304

http://archive2.tivocommunity.com/tivo- ... p?t=237478

The 2.2.5a software disables both teletext output and line 23 on the TiVo.

http://www.tivocommunity.com/tivo-vb/sh ... p?t=425360

If line 23 WSS is causing problems one workaround would be to use 2.2.5a and rely solely on the scart pin 8 switching. The AltEPG image lets you switch to 2.2.5a using a kickstart code

viewtopic.php?f=16&t=626

[The Larch]

After a bit of googling to refresh my memory -

Thanks, some interesting reading there.

If line 23 WSS is causing problems one workaround would be to use 2.2.5a and rely solely on the scart pin 8 switching. The AltEPG image lets you switch to 2.2.5a using a kickstart code

Well, parents' TiVo is on the original software, with no network card, and anyway they won't want me fiddling with it. It's working to their satisfaction after all. If it ain't broke... Thanks for the suggestions though!

I'm hoping that a little play with the engineer mode on the telly this weekend will shed some light on what's actually going on though. I'll get back if I figure anything out.

[ByTheCringe]

I found this very interesting and stimulating, so thanks very much.

[baward]

Thanks for the useful contributions to this post.

Ben

[baward]

Hmm, getting nowhere so far. I think I will have to make a matrix of possibilities, between the FV box (Sony VTX-D800U) the TV (Toshiba 37XV555D) and the TiVo as the best way to proceed.