DVD question

CaTaClYsM · Post by **CaTaClYsM** » Mon Mar 17, 2003 12:45 am

how much video can be fit onto a DVD while still maintaining the standard resolution, bitrate, and audio quality?

FurryCurry · Post by **FurryCurry** » Mon Mar 17, 2003 2:31 am

While there are standard resolutions for DVD-video, there isn't really a standard bitrate. I believe that a player must be able to sustain a transfer rate of at least 8000kbps to be considered compliant, unless its higher.

You see, you can make choices for both video and audio bitrate when you encode video to mpeg 2, and that could be anything from constant bitrates of (I don't really know what the minimum is) maybe 2000kbps, up to 8000 or higher (if you don't mind making a non standards compliant disc), or you can use a variable bitrate strategy.

The same goes for audio, in terms of format and bitrate (mp2@224,384, linear PCM, god knows what all you can use)

The real question is, "how much can you get on a disc at a quality you find acceptable?" and that is going to vary depending on your video, and what looks acceptable to you.

I've encoded my amv a couple times, one at an extreme 9000kbps cbr, and later at high quality vbr, which came out around 230mb before audio, IIRC.

I also think I recall a vob that contained an entire episode of Lain, with video, two audio tracks, and subs, coming out at around one gigabyte.

That might explain why the DVD encoding on Lain sucks, too low a bitrate.

Maybe someone more familiar with the technical details will correct or expand on some of what I've said...

Dannywilson · Post by **Dannywilson** » Mon Mar 17, 2003 2:31 am

Off the top of my head, a single sided single density disc holds a hair over 2 hours if you also include other data, such as secondary language tracks, subtitles, menu's and the like. It should be closer to 3 if it was only video.

CaTaClYsM · Post by **CaTaClYsM** » Mon Mar 17, 2003 2:38 am

yeah, 2000 bitrate over two hours. sounds right.

Synthangel · Post by **Synthangel** » Mon Mar 17, 2003 9:55 am

You COULD get one of those new Sony blue-laser recorders that store five times the normal data on a DVD disc =P They're also $3000+, but hey...go for it. Also, apparently, some Japanese companies are releasing a 1.5 TB DVD is 2010. Ok...I'll just shut up now.

RadicalEd0 · Post by **RadicalEd0** » Mon Mar 17, 2003 11:53 am

I cant do this with my vb teacher breathing down my neck

simmerdown till later n I'll set you up :\

Ashton · Post by **Ashton** » Mon Mar 17, 2003 12:52 pm

How come it is that the video on DVDs always has these black areas where there are little patches of gray? Like the encoding has a serious problem getting black to STAY BLACK.

RadicalEd0 · Post by **RadicalEd0** » Mon Mar 17, 2003 3:25 pm

ashton: either bad compression of black or NTSC only goes from luma values of 16 - 235.

Ok, DVD can essentially fit an unlimited amt of video on it and still be standards compliant :\ because! :O DVD does not specity a minimum bitrate. The max system bitrate is 9 mbps, meaning audio + video together can't go over 9mbps, but the minimum is 0. Altho.. I dont know how well encoding something at 1kbps is going to work :O..

Anyway. DVD is nice in that it offers you quite a few options for resolution and audio and stuff.
Compliant resolutions are 720x480, 704x480, 352x480, and 352x240. DVD supports Mpeg 2 for the first 3 resolutions, and Mpeg 1 for the last. Compliant audio formats are PCM, mp2 (mpeg 1 layer II), and ac3 (dolby's compression format). ac3 is the most widely used and supported, and its the best choice as far as quality goes (well except PCM, which is uncompressed :\ ). It can be stereo or 5.1 surround (if you have a 5.1 source of course).

Now. DVD was created with the intent of fitting 2 hours of video on a single sided single layer disc. This works out to 5 mbps being the most common average bitrate for 720x480 video. You could base your information off of that. The nice thing about DVD then, is if you want to fit say 4 hours instead of 2, you can just use the 352x480 resolution, which is exactly half that of the normal resolution, and encode at 2.5mbps, and get equivalent encoded quality (well relatively). Likewise, half it again to 352x240 and 1.25mbps. At this point you can fit 8 hours, losing only resolution.

Mp2 audio is best at or above 224 kbps. Ac3 audio is pretty much good anywhere, although its usually 192kbps for 2ch audio, I'm only basing that (ac3 bitrate) on what I've seen on commercial dvds. PCM is uncompressed @ 16 bits and 48khz so its always 1536kbps (16 bits * 48 khz * 2channels)

As for the video resolutions. 720x480 is the most commonly used res. I've never seen a commercial DVD use anything else. However there is a difference between 720x480 and 704x480. 704x480 should always be the amout of space the video takes up, even on a 720x480 DVD, simply because 704x480 is 4:3 on an NTSC TV which has higher-than-wide pixels (10 x 11 to be exact) (10/11 = 1.1, 704 / 480 = 1.4666, 1.4666 / 1.1 = 1.333 (4:3))
The extra 16 pixels are supposed to be black and only there to reduce the amount of actual video picture that gets cut off at the edges of TV screens.
Therefore, 704x480 is basically fine as well it just wont have the extra black on the sides. 352x480's width is doubled on playback by the DVD player. 352x240's width and height are both doubled.

Another thing to consider is framerate. For NTSC (which is what I've been dealing with the whole time :\ ) you have the choice of using true 29.97fps interlaced material, 23.976fps material that's been hard telecined and encoded as 29.97fps (what we all have on our anime DVDs), or progressive 23.976fps material with a flag that tells the DVD player to auto-telecine on playback (best choice).

But uh... >_> to answer your question, you can fit 2 hours of video on DVD at the (not standard, but) most common bitrate (5000kbps) and resolution (720x480 or 704x480)

RadicalEd0 · Post by **RadicalEd0** » Mon Mar 17, 2003 3:31 pm

Oh, I forgot to mention. Mpeg 2 looks generally pristine at 5mbps (but higher is always better). Anything bordering on 2.5mbps and under (for 720x480) is pushing it bigtime.

Btw, blu-ray can hold approximately 6x that of a dvd (~30 gb), and transfer at 6x the average datarate (~30mbps). This mainly being because the highest HDTV resolution is exactly 6x that of D1 (720x480, compared to 1920x1080). So blu-ray is basically every aspect of DVD scaled to 6x.

RadicalEd0 · Post by **RadicalEd0** » Mon Mar 17, 2003 4:01 pm

wait a minute.. you're only doing this cuz of that damn trigun box set arent you :|
fuckin bastard

the DVDs would have been encoded at 2.9mbps! geez. You shoulda just asked that.