pixel aspect ratio

[MADD]

I'm taking ota hdtv transport streams and converting to dvd spec mpeg2 files using tmpgenc. However, im not sure what pixel aspect ratio i should set for the conversion. My understanding is that the .ts streams will contain square pixels. But if im going to display the output on a 4:3 tv display, should i set it to NTSC 525 line 4:3 ratio, or just 4:3 display? The video itself is in the 16:9 aspect ratio so should i use 16:9 pixels? Input on this would be greatly appreciated.:confused:

[MADD]

Is this the wrong forum for this question?

[Karyudo]

I haven't done this myself, but I hope to be doing so soon. So I have a vested interest in how it turns out...

I believe you're right in saying that transport streams have square pixels. I've heard numbers like 12xx x 720, or 19xx x 1080 which puts them right in the native 16:9 range.

When you convert to DVD-spec video, it's going to end up being 720 x 480, which is 3:2, and you'll want to set the output flag to 16:9 for anamorphic widescreen. Any DVD player will know how to display that correctly on a 4:3 TV. And if you're lucky enough to have a 16:9 set, it'll look that much better. On the input side, I don't quite know what you should be choosing. Might have to do a few tests? But at least that's just one variable to play with, instead of two or more...

I do hope you post again with your results, however successful! (Or at least PM me?)

Good luck,
Karyudo

[Karyudo]

OK, I did a few quick tests while here at work. More exciting than what I'm supposed to be doing at 4pm on Friday...

I frameserved a 720x1280 pixel "video" (actually a BMP from OTA HDTV logo-filtered over some crap video) from VDub to TMPGEnc. In TMPG, I set the input to "1:1 VGA" and the output to 16:9, and that seemed to give correct results. I then tried it with "16:9 Source" and that was fine, too. This makes sense, because 1280x720 *is* 16:9.

In the first case, you're telling TMPG that whatever aspect ratio the (square) pixel dimensions describes is what you want at the end, and in the second case, you're telling TMPG that whatever the pixel dimensions are, you're dealing with a 16:9 source. Here, in both cases, the pixel dimensions and the aspect ratio give the same results. This is not necessarily true, though.

One caveat is that I haven't tried playing this with an MPEG2-capable software player. Here at work, I'm used to dealing only with crappy VCD-spec stuff for our promo material. (Bo-o-o-ring)

Once I get home and play with this a bit, I may have something more conclusive. "Watch this space..."

Karyudo

[MADD]

hey thanks for the reply
Ive done some testing myself, but i cant really see a significant difference between any of the output formats that i choose. The problem is that i dont have a stand alone dvd player to test on a regular tv. I play all my video through the vga inputs of my RCA HDTV and my only player is on my attached computer. So im only getting a progressive signal on what is essentially a computer monitor.

OK I looked at the HDTV football files that i encoded the this week and something is clearly not correct. While the transport stream is 16:9 widescreen letterboxed on my 4:3 display, my files play back fullscreen, though it doesnt seem as if there is horizontal or vertical compression. Its as if the player were set to pan and scan (its not). This was with video set to 1:1 pixel ratio (VGA).

BTW, why do u framserve to TMPGEnc when it will open the transport stream files directly?

[Karyudo]

BTW, why do u framserve to TMPGEnc when it will open the transport stream files directly?


I'll answer this one first, because it's the easiest! If I had a real transport stream, I wouldn't need to frameserve, I suspect -- but I don't have a real transport stream. What I have is a screen capture from a "wow-look-how-awesome-HD-is" fan page. So I used VDub to create an HD source (i.e. same picture over many frames), and served that to TMPGEnc. That's as close as I can come to copying what you've got coming right from the transport stream.

Give me tomorrow to be able to do a few more tests, and to round up all the settings I've set in TMPGEnc, and I'll be back with a report shortly...

Karyudo

[Karyudo]

OK, today I did some further checking. Here's how to repeat what I did:

Once you fire up TMPGEnc, pick a DVD template (I used NTSC Film), choose your source, etc., etc., but then don't run the processing. Instead, click on "Settings" in the bottom-right corner. On the "Video" tab, make sure "Aspect Ratio" is set to 16:9. On the "Advanced" tab, make sure "Source Aspect Ratio" is set to either 16:9 or 1:1. "Video Arrange Method" should be "Full Screen". And that's it! Go ahead and let 'er rip. Or render, as the case may be.

In my case, I got perfect, WS anamrphic DVD-spec MPEG-2, playable in WinDVD. You can grab the (very simple) result from my ftp site: 66.183.4.70, port 21, username/password: doom9/doom9. (I'm not great at setup, so you're going to have to use something other than just IE). It's the M2V file, of course...

If you still get lousy results, maybe you could make a small chunk of your source available, and I (or someone else?) could take a crack at it?

[MADD]

thx for your help. i think i have it working now. However, the superbowl threw me for a loop since it was in 720p rather than 1080i like the playoff games. Should i set the output for progressive (like the source) or interlace (like most common displays, but not mine).

[Karyudo]

Should i set the output for progressive (like the source) or interlace (like most common displays, but not mine).


You mean, in TMPGEnc? For DVD-spec stuff? I think I'd go for progressive. The player should be able to figure out what to send to the TV. It does when 24fps progressive stuff is on the disc, anyway. I really have no experience with real (that is, not originally film) 30fps sources and how they should be stuck on DVD. I can only assume ("Danger, Will Robinson!") that if lowly VCD-spec MPEG-1 can be 30fps progressive and the player figures it out, then mighty DVD-spec MPEG-2 must be able to do the same.