Low-end DVD compatability

[AlecWest]

Quality issues aside, I was curious if there's such a thing as:

1) A "lowest possible DVD-compatible video bitrate."
2) A "lowest possible DVD-compatible audio bitrate."

???

Reason? Using TMPGenc Plus, I want to convert a number of WMV files to MPEG2 and later burn them to DVDs. The WMV source files are all 300kbps video and 48 kbps mono audio (44khz). This may seem silly, but I intend to center the 320x240 image in the 720x480 TV screen when I encode. In short, it will be like letterboxing all the way around.

I've done this before successfully ... BUT ... I've always encoded at higher A/V bitrates and want to know how low I can go before authoring tools won't buy it ... or before DVD players won't buy it.

[mats.hogberg]

AFAIK, there's no lower video bitrate limit, and the audio lowest value is 32 kbps according to "What Is".
I should think this is what the DVD Video specs says.
What the individual DVD player make/model accepts, I suspect is another story!

/Mats

[guns1inger]

That said, you will suffer more if you encode full frame (even if you have kept the video to it's original resolution) at low bitrates. I'd be encoding to a lower resolution if you wan't to keep the bitrates low.

[the * dude]

yeah the lowest video bitrate is 0,

ur source is 320x240, why don't you encode the dvd in 1/2 d1 (vcd quality), you'll get a full screen picture comparable to an original vhs tape.

[Richard_G]

If your source is 320 x 240, you can go down to about 1500kbs without too much degradation. You are using slightly under a quarter sized resolution (compared with full frame) so a quarter of the bitrate will be fine. You'll get no more artifacts than full frame at 6000kbs. If you can afford to bump it up to 2000kbs, it will be about as good as you will get with an original in that resolution.

[non-linear]

ur source is 320x240, why don't you encode the dvd in 1/2 d1 (vcd quality)

Actually, 352x240 would be 1/4 D1. Half D1 is 352x480. That said, I would recommend encoding those videos at 1/4 D1, that way all the data is being used for the actual video, plus you can see it full screen instead of filling the screen with black and wasting bits to encode that.

[guns1inger]

I suspect part of the problem is embedded subtitles that will get lost in the overscan if he goes to 1/4D1

[AlecWest]

Well, this calls for an experiment. Here's what I'm going to do ... and I'll report back when I'm done.

First, I'll create a 2000 kbps MPEG2 file, full-screen, at 1/4D1 ... centering the 320 pixel width within a 352 pixel window so it's copasetic (with tiny black bars on the side). Then, with the same original file, I'll create another 2000 kbps MPEG2 file with the 320x240 picture centered in a 720x480 window.

What worries me is that stretching out the 320x240 display to fit a full screen will be worse than VHS. While I've successfully converted former VCD files into DVD without too much pixelation, those VCD files started out with an 1150 kbps video bitrate ... and the WMV files I'm using are only 300 kbps. But, I'll let the end product(s) speak for themselves.

P.S. If anyone's interested, I'm doing this as a Hanukkah present for one of my Jewish clients. The videos I'm downloading come from this site:

http://www.israelnationalnews.com/tv/israeli-salad/salad1.html

"Israeli Salad" is a cultural program kinda like a lot of local public interest shows on US television. Arts, crafts, music, etc., etc. are highlighted. BTW, if you try to access the videos via Firefox or Netscape, you might run into a dead end. MSIE handles the site coding beautifully, though.

I'd sent her a few shows earlier in WMV format on CDs and she loved them. Well (ahem ahem), using Net Transport, I downloaded every single show from the site ... from show #1 to show #94 ... and want to send her the whole collection on DVD. At the same time, I don't want to send them if they're "blurry" ... and if the full-screen presence isn't that good, I'll revert to a centered screen presence. Hehe, and given the number of shows I have to reencode, it'll take me until Hanukkah to do it.

[AlecWest]

P.S. The first file has been reencoded (full-screen) and, based on its size (if it's not blurry), I can fit 9 shows on each DVD with each show being approximately a half hour. But, I'm also trying one other experiment. Since the WMV files are 300 kbps, I'm creating another MPEG2 file at 300 kbps ... both to see how it looks in comparison to the 2000 kbps file and also to see if my DVD player "coughs" while trying to render that speed.

[non-linear]

I suspect part of the problem is embedded subtitles that will get lost in the overscan if he goes to 1/4D1

He made no mention of subtitles.

First, I'll create a 2000 kbps MPEG2 file, full-screen, at 1/4D1 ... centering the 320 pixel width within a 352 pixel window so it's copasetic (with tiny black bars on the side).

I don't understand why you're pillarboxing these. 1/4 D1 NTSC calls for 352x240, and when it's watched on TV, the image will be the proper aspect ratio. Putting the bars on will squish the picture.

You're worried about the quality looking worse than VHS. Well the reality is that your 300Kbps wmv files are guarenteed to be worse than VHS anyways, so you're not going to get VHS quality, no matter how high a bitrate or resolution you encode at. Also, I don't think putting the video in the center of the screen will do any better. It's highly compressed video in low resolution; there's nothing you can do except either live with it, or just don't encode them.

What I would do in your situation is encode them as 1/4 D1, 2 pass VBR, probably at 1500Kbps average, or 2000Kbps average at the most.

[AlecWest]

It's highly compressed video in low resolution; there's nothing you can do except either live with it, or just don't encode them.

That's definitely an option (not encoding them). If everything looks like crap, I'll scrap the project and just burn the WMV files to CDs ... and tell her she'll just have to watch them on her computer. But, I've had some luck with WMV files before so I'll at least complete the experiment.

[AlecWest]

OK ... the results. First, the MPEG2 files I created at 300 kbps (like the WMV files) have been deleted. I didn't even try to burn them ... they looked that bad. The files encoded in 1/4D1 (full-screen) were between fair-looking and poor-looking. But, when I centered the 320x240 image in the 720x480 file, it looked pretty good. Further, when I used my DVD player's "zoom" button on the remote control (1 setting up size-wise), it retained enough quality to make it worth watching ... with only 3-4" of letterboxing all around on my 27" TV. So, I'll just have to remember to tell the lady to use her player's zoom button (one-level-up) if need be.

The experiment wasn't without "issues" though. One video issue remains ... but it was expected. Fast movements "flutter" on the screen. Fortunately, the type of videos I'm encoding don't have many fast movements in them. It's mostly people talking to other people. And initially, there was one audio issue. Audio and video were approximately 3 seconds apart. I suspected that was because I chose such a low bitrate to re-encode the audio ... 48 kbps mono, just like the WMV. So, I re-encoded it again, this time setting audio at 224 kbps stereo and the video bitrate upped to 3000 kbps. The flutter was slightly lessened ... BUT ... the audio sync issue disappeared almost completely.

At 3000/224, I should be able to get 7 half-hour shows on each DVD.