352x480 is stretched too much

[qlizard]

I've been trying to determine which resolution to use to encode my VHS material, because of the obvious savings in bitrate using half D1. I have captured the material through my DV camcorder at 720x480. After filtering with virtualdub, I use procoder to encode and resize. I have been trying to compare quality of 704x480 (7000 2xVBR) vs. 352x480 (3800 2xVBR). I have observed that when the encoded files are "stretched" to DVD compliance, the 352x480 is "overstretched" and is slightly wider. The easiest way I found to observe this is by importing both files into adjacent video tracks in premiere and clicking the "toggle track output" button to see the differences. but I see the same effect if I use VS7 or even when I play the files on a media player. It appears to me that being slightly wider makes the resulting video appear less sharp.

Has anyone else observed this? Is there a way to prevent it? I think that without this effect, the quality of half D1 and full D1 would be about the same for VHS sources.

I'm also going to try and determine if it as a function of Procoder, or if it is inherent in that particular resolution.

[pijetro]

What version of Premiere are u using??

[qlizard]

What version of Premiere are u using??

Premiere Pro 1

[pijetro]

the 352x480 is "overstretched" and is slightly wider

Alrighty, i'll guess at a few things, but you'll have to take it from there..

Your DV is a .9 pixel aspect ratio, thus perhaps effecting what it loks like after encoding.
Try capturing with Huffy, or something with a 1.0 PAO, and see if there's a difference in "stretchiness" after encode.

As far as that's all concerned, don't judge by Premiere, especially if you're putting encoded material on the timeline.
The true test will be on your television set (which i'm guessing is correct)...

Good luck!!!

[FulciLives]

My understanding is that the proper way to resize from 720x480 to 352x480 is to first crop 8 pixels off either side so you end up with 704x480 then resize from that to 352x480

However assuming this is correct then resizing direct from 720x480 to 352x480 would result in the picture being slightly "crushed" as opposed to "stretched" in that your 352x480 gets stretched back out to 704x480 for playback ... not 720x480

However that is based on what I've read ... it's not confirmed.

It is possible that 352x480 gets stretched to 720x480 but it seems unlikely from what I've read.

- John "FulciLives" Coleman

[lordsmurf]

Your situation is an anomaly, not the rule. Sorry, no time to help, thought I'd throw that in. Good luck.

[qlizard]

ok, I've tested this a little more and it continues. I want to test it further by adding in a couple of blank pixels on either side of the video. I can't see how to do this in virtualdub. Any ideas?

[pijetro]

Video>Full Processing

Video>Filters>add>resize

[qlizard]

alright, I thought that was just for stretching or shrinking, but it looks like using the "expand frame..." checkbox is what allows you to add some blank space to the sides. Is that right?

[qlizard]

And now when I'm trying it, I'm seeing that vdub will not let me resize it. I'm using the panasonic codec, but whether I use it or the canopus DV codec, it says "the source image format is not acceptable". I can resize if I use a non-DV codec, and I can do other vdub filters using the DV codecs, but it will not allow me to resize using a DV codec. I guess the size is built into the codec.

[pijetro]

DV is 720x480, so i'm guessing this is the reason.
However, if you want to crop, and resize, do this..

Filters>Add>Null Transform>cropping(pick the values)
and then
Filters>Add>resize, you might have a bit more luck

[qlizard]

I didn't really want to crop anything, I wanted to add blank space. But for now I'm going to crop a little off the top and bottom and resize as usual with procoder just to test it. thanks for the help.

[qlizard]

won't let me crop either, while using a DV codec.

[Alan69]

I've been trying to determine which resolution to use to encode my VHS material, because of the obvious savings in bitrate using half D1. I have captured the material through my DV camcorder at 720x480. After filtering with virtualdub, I use procoder to encode and resize. I have been trying to compare quality of 704x480 (7000 2xVBR) vs. 352x480 (3800 2xVBR). I have observed that when the encoded files are "stretched" to DVD compliance, the 352x480 is "overstretched" and is slightly wider.

? Um, HUH?

Ok, let's clarify. You are comparing your generated 352w file to a 704w file, and thinking the difference in clarity comes from it's being slightly overstretched vs the 704w? It's only 352 pixels instead of 704, it will be less sharp. The 352 to 704 width doubling will be done by timing, and may be a bit off to make your slight width difference between the 704/720 and the 352 files, but that slight difference in width isn't where the sharpness loss is coming from.. Maybe I'm reading what you're saying vs what you're actually doing wrong..

Yes, you're doing the same steps for both. But 704 is very near 720, you aren't doing much to the video beyond a reencode. With 352 you're reencoding and merging 2 pixels into 1, of course it will lose a lot more detail, you can't cut the bitrate in half without losing a lot of something.

You simply can't compare a 700+ file to a 352 file and expect the 352 to hold up. You have to evaluate the 352 on it's own, is it acceptable or not? I can see the lower clarity of 352 even on a bad TV, I only use 352 for things I don't care about much at all. And it does help slightly to get it to 704 first then 352, since that will make a direct 2 to 1 pixel merge so avoids the slight extra quality loss from the 720 to 2x352 mismatch. And you do need to crop for this. Making blank space will just leave blank space in the 720, and still leaves the 720 to 2x352 mismatch. You generally need to cut it to 704, then use that to make the 352 for best results.

" I think that without this effect, the quality of half D1 and full D1 would be about the same for VHS sources."

No way in heck is this the case. 352 can look ok by itself. Put it beside a 640 or 704 or 720 though and you'll spot the clarity difference instanty if you look at the general image. Even a 220 line VHS tape and a 220 line TV are both analog and not pixelized at 220 dots. You can see the 352 vs higher capture difference even on a junk tape or TV. 352 just looks blurry vs a higher horizontal res, part of why I rarely use it. I guess a really crap source you may not be able to tell, but I haven't found a source that bad yet.

Alan

[johns0]

Try encoding with tmpgenc to see if it comes out at the proper screen ratio at 352x480,i capture at 720x480 avi and get the squeezed look but after the encoding the result is the proper size because the screen was properly resized vertically during the encode,maybe procoder isnt doing this right.

[qlizard]

You simply can't compare a 700+ file to a 352 file and expect the 352 to hold up. Alan

It appears several on this forum don't agree with this, that VHS doesn't have the "resolution" to begin with, and anything over 352 is overkill. I agree with you, though, that I see a difference in sharpness, and was trying to test if it was because of being stretched too far.

And it does help slightly to get it to 704 first then 352, since that will make a direct 2 to 1 pixel merge so avoids the slight extra quality loss from the 720 to 2x352 mismatch. And you do need to crop for this. Alan

This is interesting, and I hadn't been doing in my conversion to 352. But how do I crop if virtualdub won't let me do it using a DV codec? I would think it bad to use another codec for DV material.

[Alan69]

You simply can't compare a 700+ file to a 352 file and expect the 352 to hold up. Alan

It appears several on this forum don't agree with this, that VHS doesn't have the "resolution" to begin with, and anything over 352 is overkill. I agree with you, though, that I see a difference in sharpness, and was trying to test if it was because of being stretched too far.

Few people look much beyond the basic idea of such measures though. 'Lines' is not pixels. Lines is where 'above that and a black/white line plate will grey out'. Above a certain limit of black/white transistions and the bandwidth of the circuitry and/or the dot pattern limits it and it just goes grey. But the TV is analog, a pixel doesn't have to be all one 'color' The 'R' part could be black, then the pixel turn on for the 'GB' part, just like sub pixel cleartext stuff for a laptop screen. The edge positioning of the dots can be in more places than the highest number of full 'pixels' on the screen. Guaranteed to happen since it's analog and there's no restriction on exactly when a pixel turns 'ON'.

But the sharpness loss isn't really from being 'stretched', it's from turning those two side by side pixels into only one pixel. The lower resolution can't capture the edge detail as closely as the higher, and even if it's only 220 'lines' the edge detail is higher. Lines are great for comparing two TV sets etc, but it's not the highest possible detail you can see from the set. It is only what it is, the highest number of FULL black to white transistions it can display clearly. Even with that, you can shift the 'lines' timing just a bit, and have them go from being 'RGB' dots to 'GB and next R' dots, etc. That guarantees you can have a 'sub pixel' res of 660 with the 3 RGB sub pixels on a 220 'line' set. And you'll see you didn't capture those edges just right if you only have 352 pixels. Still can look 'fine' but won't with a 700+ capture to compare it to.

And it does help slightly to get it to 704 first then 352, since that will make a direct 2 to 1 pixel merge so avoids the slight extra quality loss from the 720 to 2x352 mismatch. And you do need to crop for this. Alan

This is interesting, and I hadn't been doing in my conversion to 352. But how do I crop if virtualdub won't let me do it using a DV codec? I would think it bad to use another codec for DV material.

I don't do DV so can't say for certain. With full processing mode, you should be able to do DV in, the crop, then something else out. Still, not sure, may need to go some other route than just VirtualDub.. Hey make a small clip from the original and stick it some where, I like using VD so would take a look at it myself just to see.

Alan

[qlizard]

Hey make a small clip from the original and stick it some where, I like using VD so would take a look at it myself just to see.

Not sure how to post a file. I'll try to figure it out because I know I'll eventually have to if I want to continue this "hobby".

Still can look 'fine' but won't with a 700+ capture to compare it to.

Alright, I think I'm pretty much convinced that I should encode my VHS material at full D1. But now another question. I don't really notice many people using resolution 704x480. It would seem that you could save a little bitrate this way. Is it ok just to resize down from 720 to 704 during encoding (without cropping)? If so, and for example I was using 7000 VBR at 720x480, at what bit rate (roughly) would I get the same results at 704x480?

[SatStorm]

When you capture the higher your card can, filter, resize the correct way and encode to 1/2 D1, then you have what VHS and SVHS can give you.

But that doesn't mean that your DVD Standalone gonna show it to you. The DVD standalones have to support all the "official" framesizes of the DVD specifications, but that doesn't mean that they are doing it the very best way.

I'm able to see a 1/2 D1 DVD clip from a VHS source on various DVD standalones, and the differences between them are obvious. There are DVD standalones that shows the example bad (blured for example) and others excellent.
The situation is even worst for interlace 352 x 288, but this is another subject, not for this post.

Anyway, here is an easy test to do, if you wish to see with your own eyes the easy way why 352 x 480/576 is near - VHS.

Try to capture using the Mainconcept 1.4.2 demo realtime to mpeg 2.
Set for the input the higher framesize your capture card can (768 x 576 for example) but for output set the mainconcept engine to convert to 1/2 D1 with 4000 CBR (the "ideal" bitrate for that framesize).
You'll be amazed with the results and with the fact that the final mpeg 2 has an excellent sharpness.

Anyway, after countless hours of discussions at this and other forums, the conclusion is that there are too many variations to consider when you do such a convertion. If you don't wish to deal with all those things and issues, then better capture and encode straight to D1. After all, 2 Hours per DVD is fair enough for most users....

[Alan69]

Still can look 'fine' but won't with a 700+ capture to compare it to.

Alright, I think I'm pretty much convinced that I should encode my VHS material at full D1. But now another question. I don't really notice many people using resolution 704x480. It would seem that you could save a little bitrate this way. Is it ok just to resize down from 720 to 704 during encoding (without cropping)? If so, and for example I was using 7000 VBR at 720x480, at what bit rate (roughly) would I get the same results at 704x480?

Would be around the same percentage as 704/720. But I wouldn't bother with it, the reduction is very minimal for 16 out of 720.


And ignore Sat and anyone else telling you different, these people simply regurgitate what others have told them. They don't do electronics, and they have no basic understanding of the difference between pixels and analog lines of resolution.

As always the ultimate idiot check to make yourself sure, cap in 352 then cap in 704/720. If you can SEE the difference in clarity then of course there is info on the tape that isn't being caught by 352. These people are just clueless about what 'lines of resolution' are and analog systems and spouting crap as knowledge.

Alan

[SatStorm]

I would say something different: Ignore all those who don't know how to rise their opinion, without attacking other members of the forum.

You can't trust people of that kind in real life, why to trust them at the forum?

Just let them at their misery...

[johns0]

Alan69,i would rather llisten to SatStorm over you anyday,he has written guides and helped lots of people here and has been made a mod recentley for his efforts,you on the other hand insult him for whatever reasons i cant figure.

[SatStorm]

I would say that he has a theoritical approach of the subject and that turns to problem after a while when you have to deal with the mainstrem hardware / software.

As always the ultimate idiot check to make yourself sure, cap in 352 then cap in 704/720. If you can SEE the difference in clarity then of course there is info on the tape that isn't being caught by 352. These people are just clueless about what 'lines of resolution' are and analog systems and spouting crap as knowledge.

Typical : "I know the theory, this is what the book says, this is how the things are"

It is obvious that he is only on theory from this sentence and posts like this https://www.videohelp.com/forum/viewtopic.php?t=199669&highlight=
are scandalous!

I bet 8 centuries ago, he would burn alive anyone said that Earth is round.

[qlizard]

Sat (and others),
forgive me if I seem incredibly naive on this subject, but when I pull up material encoded from the same source, but at different dvd-standard resolutions and play it on media player, they play at slightly different widths. It causes it to appear slightly different. For example, using a DV avi (720x480), and encoded to different resolutions: when I pull up a sample encoded at 352x480, it is slightly stretched compared to the original. When I pull up one encoded at 704x480, it is slightly shrunk in width. Just for a test, the output encoded at 720x480 is exactly the same. I haven't actually tested this on my standalone dvd player, and am not sure how I would.

And now, according the the very interesting thread you posted, using a DV source (which starts at 720x480), would it actually be better to resize down to 368x480 and then crop to achieve 1/2 D1? But it appears the content of that thread is totally chip dependant so it may be irrelevant in this case.

[SatStorm]

- edit - I read your post more carefull

It seems that in your case, capturing 720 x 480, resize to 344 x 480 and expand to 352 x 480 gonna give you a better aspect ratio.

Try to contact fulcilives about this subject (he is an advance member of this forum). He did an extremely research about this subject. Nobody can beat him about this.

[FulciLives]

Sat (and others),
forgive me if I seem incredibly naive on this subject, but when I pull up material encoded from the same source, but at different dvd-standard resolutions and play it on media player, they play at slightly different widths. It causes it to appear slightly different. For example, using a DV avi (720x480), and encoded to different resolutions: when I pull up a sample encoded at 352x480, it is slightly stretched compared to the original. When I pull up one encoded at 704x480, it is slightly shrunk in width. Just for a test, the output encoded at 720x480 is exactly the same. I haven't actually tested this on my standalone dvd player, and am not sure how I would.

And now, according the the very interesting thread you posted, using a DV source (which starts at 720x480), would it actually be better to resize down to 368x480 and then crop to achieve 1/2 D1? But it appears the content of that thread is totally chip dependant so it may be irrelevant in this case.

I think I understand the problem now!

You are testing with Windows MEDIA PLAYER which is a poor choice for playing back any MPEG file.

Try testing it with PowerDVD or WinDVD instead.

As for HALF D1 you need to crop from 720 width to 704 width then resize to 352 width. That should give you a proper aspect ratio.

That thread you read was mostly about BT based cards ... shouldn't apply to DV captures.

- John "FulciLives" Coleman

[qlizard]

I am actually using Media Player Classic, which I prefer to those other bloated programs. But I also have WinDVD, and had previously tested on it. Regardless of which player, and in the preview windows of both premiere and Videostudio, the encoded 352x480 is slightly stretched, and the 704x480 is slightly shrunk compared to the file encoded at 720x480 (which ends up identical in width to the original). If you test it and tell me that you see no difference in how much the different resolutions take up in your player window then I'll shut up about the whole thing and move on.