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Discussion in 'Archived Threads 2001-2004' started by John-Miles, Aug 26, 2002.
I confirmed this with an RP-91
It is possible that the Toshiba is handling anamorphic content by throwing away 25% of the scan lines. That's what the Hitachi sets do. Given the 540p upconversion that I believe the Toshiba does, it would mean that the 480i/480p signal is resampled to 540p, then a quarter of the lines removed to make it the right aspect ratio. That would produce, in effect, a 405p signal (although it may be further line-doubled to 810p as in the Hitachi).
You wouldn't be able to know that from examining the aspect ratio of the resulting image, which would be correct. But you should be able to do it with an Avia resolution pattern and comparing it "squeezed" and "unsqueezed" and making sure the resolution is that same. I doubt that it is.
If you already took this into account in making your original post, then I apologize for doubting your results...
No I never took that into account, infact I knew nothign about this. I posted this because a number of people were curious as to ifthe HFX71 model would do the squeeze on a 480p signal. which i confirmed it does. i guess i will have to wait till i can borrow a progressive scan player again to chek the resolution with my avia disc.
ahhh the problems of not having enough money for the good tv AND dvd player.....
You could still check the same thing on 480i. Use the 200 TVL resolution pattern on Avia.
1) Set the DVD player to 4:3 and see where on the horizontal wedge the picture runs out of resolution.
2) Then set the DVD player and the TV to 16:9, which if the DVD is enhanced should provide the extra lines. Check the wedge and you should see that the resolution is improved noticably.
3) If not, then set the TV to 4:3 mode with the player still in 16:9 (now the picture will be "too tall" because you've turned off the squeeze) and check the wedge again. If this resolution is better than it was in both Step 1 and Step 2 then you might suspect that the TV is throwing away 25% of the scan lines for you, much like the way the DVD player does if you set it to 4:3.
There is, of course, still the possiblity that the TV downconversion (if that's what it does) is better than the one in the player. But it's awfully hard to fool that 200 TVL resolution wedge. Even if the TV is ending up with 405 or 810 actual lines, I think that waiting until the last step to throw away the lines will produce a better picture than letting the DVD player do it before the TV does its upconversion and so forth. That would probably be more noticable with real-world content than with a resolution test pattern.
I will check that tonight and post the results, thanks Brent
I don't believe the 2001 Toshiba HDTV-ready direct view sets upconvert 480p to 540p. In addition, the 4:3 Toshiba HDTV-ready sets have two different 16x9 modes according to the manual: letterbox, and widescreen or something like that. Letterbox sounds like it is throwing away 25 percent of the lines while widescreen is shrinking the raster and putting the entire image into the 16x9 area. Why an 4:3 HDTV-ready set would only do a letterbox option is confusing to me since dvd players will already do this for you - in the digital domain before converting it to an analog signal. In addition, it seems like a real option that users want to have. It seems it is the reason a lot of people choose to buy the current crop of Sonys.
John, you should be able to use these two different modes during your testing.
Blah.... that letter box mode is useless...... it makes animorphic dvd's smaller.... the only modes that are any use at all are the compression and the normal mode.
at least in my humble opinion. but I will check the letterbox mode to see if ti is tossing away resolution.
what exactly am i supposed to look for on the 200 TLV chart?
John, there are directions attached to the Avia patterns and that should explain exactly what to look for when measuring vertical resolution (you're not interested in horizontal resolution).
Yeah i read the directions... but they didn't seem to say much... maybe i missed some of the directions, but all it seemed to say was what was on the chart. oh well i will keep looking i guess.
John, I'd have to take out Avia this evening and take a look at that pattern to recall exactly what you're looking for. But I'd say the Toshiba does do a raster squeeze, if only because if it didn't, then there would be no difference between their "letterbox" mode and their "compression" mode. If the latter isn't doing a squeeze then exactly what is it doing?
I agree with Tom that the presence of both "compression" and "letterbox" modes implies that one of them must be a real squeeze.
However, what I had in mind for comparing modes using Avia is to go to the "Widescreen Enhanced" menu and choose the "Resolution" image. This is the same picture as the "200 TVL" screen but I didn't remember that it was named differently under the "Widescreen Enhanced" menu.
Anyway, on that image there are two horizontally-oriented wedges. The idea is that the narrow end of the wedge requires about 400 lines of vertical resolution to reproduce clearly. The ones on the "Widescreen Enhanced" menu are 480-line images that are vertically stretched. So you can view them in regular 4:3 mode (looks too tall) and confirm that you can clearly resolve the 400-line end of the wedges. Then switch your TV to squeeze mode (aspect ratio of the chart will now look right) and make sure you can still make out the 400-line end of the wedges all right.
If the narrow end of the wedges blurs together in squeeze mode, then your set is doing the fake squeeze by throwing away 25% of the lines. Maybe that's what Toshiba would do on "Letterbox" mode.
My only concern is that the 400-line end of the wedge may not be fine enough lines to clearly show the difference. I say that because when I choose "4:3" on my DVD player, which should do the downconversion, the 400-line end of the wedges are still clear. That seems strange.