Each DVD will hold 120 minutes at "SP" speed,

Not true. Commercial DVDs are dual layer. The DVDs you burn yourself are single layer and only hold abougt half as much.

I think you misunderstoof me (or I misstated me;-). I realize the AVI needs to be encoded to MPG2, which Roxio was doing prior to burning. The problem is, after encoding, the files are too large to fit on one 4.7 gig DVD-R. John Meyer said below that consumer DVDs only hold about one hour, but the DVDs I am using state clearly they are 120 min. at SP quality, so now I am really confused.

Let me ask you this: are you able to burn two hours of DV footage on a single 4.7 gig DVD? I was under the impression that this was possible, but maybe my impression was incorrect.

John, I am a bit confused. The DVDs I purchased are Memorex 4x DVDs, 4.7 gig capacity and clearly state they will hold 120 min. at SP, longer at EP (240, I believe). Am I missing something?

SP and EP are tape speed terms, don't really mean much in the digital video world. I am not sure what they are referring to, but a DVD is limited by file size, not by tape speed.

Dave T2

"SP and EP are tape speed terms, don't really mean much in the digital video world. I am not sure what they are referring to, but a DVD is limited by file size, not by tape speed."

Yep, I thought the same thing, but I think what they are doing is using the tape terms for their DVD media, to keep things easy for the consumer. I just checked their site and they don't mention SP, but they do mention 120 minutes of video capacity.

They say in SP and EP speeds for those set top DVD burners, they really have no meaning when it comes to burning DVD's on a PC. That said, you can still easily get 2hrs or more of good quality video on a 4.7GB DVD-R using a computer. The 2 things you need to worry about is the video bitrate, keep it around 4Mbps, and then the audio. In order to get 2hrs on a DVD-R you will need to use AC3 audio not PCM. I haven't used DVD-A but I will assume that it has the capability to mux your audio stream into a AC3 stream.

I know for a fact that Roxio was using PCM for audio, so that will help. I am not sure about the video bitrate; unfortunately, it only has high and low (it came with the burner and is hopefully only temporary). I'll try high compression and see what the quality tradeoff is and see if I can determine what bitrate it is using. Thanks for your help...

Ghost, goto www.dvdrhelp.com. They have a section that you can use to estimate the size of your finished mpeg file. I use it sometimes. Also, your burning program may have a min/max encoding setting. I found out today that my ArcSoft software that came with my burner re-encode all my mpeg's to 6.800.000 bitrate no matter what i render them to. .

No, DVD-R, for example, will hold up to 120 minutes.

What have you done for the menu?

I really hate these cheap DVD software programs that don't allow you to have control over your videos once you put them in there. They use PCM audio, give you 2 or 3 settings for your video bitrate, and then recompress your already compressed video for no reason at all.

All DVD software should have a setting that allows you to use the video and audio stream that you import without re-compressing it.

I believe this is the bitrate calculator you are referring to

http://www.dvdrhelp.com/calc.htm

But even that doesn't account for the diffrences between PCM and AC3 audio, I think it only calculates PCM which isn't very useful.

Good, Friar, where in all that information at dvdrhelp.com might one find the page that enables you to estimate the size of your finished mpeg file?

Thanks!

J--

If it is all one file it is still going to be PCM audio, in order for it to be AC3 audio there needs to be a seperate video and audio file.

I do all my DVD encoding and authoring on a Sonic Fusion system so I never bought DVD-A just the standard Vegas upgrade. I'm sure there is someone out there that can tell everyone what settings you need to get AC3 audio out of Vegas. Or maybe it's just not possible using Vegas+DVD to generate an AC3 audio track, but I would assume if it can do 5.1 audio that it can make a AC3 file.

PCM is fine if you need to get an hour or less on a DVD-R, there is really nothing wrong with it. But if you want to get more than an hour on 1 DVD-R and still have good quality video you need to use AC3, the PCM file size is just too big to allow enough space for the video at a reasonable bitrate.

I'd assume there is a big licencing fee with the AC3 audio and that is why a lot of the cheaper authoring packages can't include it.

AC3 isn't just for surrond sound. I hate to use this comparison becasue sometimes people get the wrong idea, but you can kind of compare it to a .wav file is PCM and a MP3 is AC3, now I know that a MP3 is not a AC3 file, but if you look at the file size of a wav file and a mp3 file they are completely diffrent and to most people sound the same. That is what AC3 is, basically a compressed version of the PCM file. IF your audio file is smaller, then that leaves more bits on the disc for video. And to kind of revise my previous statement, you can get more than an hour of good looking video and still use PCM audio, normally it's between the 1 hour and 90 minute mark that you will start to compromise your video quality to make space for the PCM audio. It all comes down to what you think is "acceptable"
A lot of my clients are extremely picky and "acceptable" to them means no blocks in the videos, no dropouts, they basically want their DVD to look just as good as their master tape.

No, in order for you to play back a MPEG-2 file with audio on a computer it would have to have the audio and video all in one file. If you had the 2 seperate files the video would be a .m2v file and the audio would be a AC3 file. You could probably click on the .M2v file and it would play back through Windows Media Player, but it wouldn't recognise the AC3 audio and play it back along with the video. You will either need to author the DVD, or make a single MPEG-2 file. Probably the cheapest software that you would be able to get that will encode your audio to AC3 is DVDit, it is around $300-$400 depending on what version you get.

http://www.dvdit.com/

Also DVD-A might do it, I just don't have the software so I can't confirm that it will, and I think the upgrade from Vegas 4 to DVD-A is cheaper than DVDit

The first difference is that manufacturers of media & computers use different counting rules.
Media manufacturers count a Gb as 1000x1000x1000
Computer's use binary system so a Gb is 1024x1024x1024
Your 4.7Gb disc is therefore reported as 4.37Gb on the computer.

Then to help with bit budgeting I follow the following:-

A 4.7Gbdisc has 37,600 Megabits available.
When I first started authoring DVDs I read that I should allow 4% for overheads (navigation data, still menus etc)

Take 4% from that & you have 36,096 (Make it a nice easy round number without losing too much & you have 36,000)

So we have 36,000 Megabits to divide equally amongst all the seconds in our movies that are to be included in our project. That would give us the average bitrate for all our movies (video & audio)

Because we are working in seconds (& that's a lot of numbers) we can make it easier so instead of working on 36,000/number of seconds if we divide both sides of the equation by 60 we get

600/number of minutes = average bitrate.

An example is
600/120 minutes = average combined bitrate of 5.0Mbs
If audio is ac3 at 192kbs that would leave average bitrate of 4.8Mbs for video
If audio is PCM at 1600kbs that would leave average bitrate of 3.4Mbs for video

As I said earlier the 4% ovrehead doesn't include motion menus so you'd have to add them as movies.

I don't know about you but I'm quicker dealing with small numbers than big numbers. This method provides a fairly accurate way of maximising the available space on your disc, whilst maintaining quality. It's never failed me & that's why I pass it on.


A couple of other things of note

For compatability reasons when doing small projects I don't use as high a bitrate as this formula may allow. This is because I don't want the playback device pushed to the limit (it may result in skipping during playback)
The maximum combined bitrate you can use is 9.8Mbs but I would use a combined rate lower than that even if space allowed higher. Say 9.0Mbs. At that rate you shouldn't notice any quality hit but you are taking the strain off the decoding.

If you are adding multiple language tracks & subtitles, these will have to be catered for in your original figure for the AVERAGE bitrate.

The space on the different DVD discs is as follows:- (media manufacturer counting)
DVD-5 single sided,single layer; 4.7 GB
DVD-9 single sided,dual layer; 8.5 GB
DVD-10 double sided,single layer 9.4 GB
DVD-18 double sided,double layer 17 GB

The dual layer discs can only be pressed at replicating house not made on a PC with your burner.

The SP modes (minutes available) mentioned earlier do not relate to your authoring DVDs on a PC. These relate to recording "SP" mode on a stand alone DVD Recorder/Player & will give you approx that many minutes in that mode of recording.

Oh & VideoCurmudgeon here is the address of the dvdrhelp bitrate calculator if you find that easier
http://www.dvdrhelp.com/tools?tool=3#comments

Not a problem, DVD can get very confusing!

Thanks to everyone for the help and amazing answers. It would have taken me days to make heads or tails of all of this searching the web...

No problem, a lot of the software to make DVD's these days really "hides" the users from how advanced making a DVD actually is. If you really want to know everything about DVD's I would highly reccomend picking up a copy of the book DVD Demystified, it is a great learning tool for all things DVD.

Got it. Thank you.