What's the time limit on a DVD?

[PlayWithFire]

This is a really stupid question, i know, but i can't find the answer.
Is there such thing as a time limit on a DVD? Or will the quality just degrade if i add too many movies to it? I am using DVD Styler to create some stuff, and was wondering if there's a time limit i should try to stick under, or will it just compress everything at the cost of quality?

Thanks!

[bendixG15]

nm

[CobraPilot]

Time limits on a DVD are roughly analagous to VHS recording: If you record the same program at the 2-hour speed, it'll look a lot better than it'll look if you record at the 6-hour speed. Your eye will determine if you're willing to compromise quality for being able to put 3 2-hr movies on one tape.

I have a standalone DVD recorder with 1-hr, 2-hr, 3-hr, 4-hr, and 6-hr speeds. The longer the recording time, the more degraded the video results. The 6-hr speed seems roughly to the 6-hr VHS speed, maybe a little worse; viewable, but not great.

Personally, I can't see much quality loss from the 1-hr to the 2-hr recording time. The video looks a little poorer at the 3-hr speed, and maybe just a little worse than that at the 4-hr speed. If I thought I might want to save something I recorded to watch more than once, I wouldn't go lower than the 4-hour mode. I'd only use the 6-hr mode for some very long program or series of programs that I'd just watch once and then discard.

The same holds true for recording on a PC to a DVDR/RW: The more time you squeeze onto the disc, the worse the video will look because of the necessary compression via any one of the various video recoders/transcoders available.

What I'm about to write will drive the purists mad: To my eye, on a large-screen (42") TV, I find that I can hardly tell the difference with DVDs using compression ratios as low as 52-55% of the original.

"Beauty" (the acceptable quality of the resulting video) is always in the eye of the beholder and "your mileage may vary."

[CubDukat]

If I'm not mistaken, the official DVD spec will give you 2 1/4 hours per layer at the max bitrate of 9000. Obviously you can get more material on a disc with more agressive compression, but there will be a trade-off in image quality.

In my own experience, I've been able to encode 1080i HDTV shows with bitrates as low as 5000 with acceptable results, which will give you about six episodes to a dual-layer disc. You really do not want to go much lower than that, though.

Obviously you're not going to shoehorn eight hours of video onto a DVD and have it be anything other than barely watchable. That's not to say it can't be done, mind you; it's just not advisable.

For my own encodes, I usually keep my average bitrate around 6500 and the high end at 8000-9000, which gives me two episodes per disc, but with extremely high quality.

Hope that helps you out.

BTW, if you don't have a whole lot of movement in your material, you could probably get away with a lower bitrate, but if you're encoding something like "24," you're going to be on the high end of the bitrate scale for the most part.

[guns1inger]

If I'm not mistaken, the official DVD spec will give you 2 1/4 hours per layer at the max bitrate of 9000

The spec doesn't work in time increments. It speaks of bitrates and resolutions. How you use these determines the amount of time vs quality you can get on a disc. At the maximum video bitrate of 9800 kbps you can get approx 60 minutes to a single layer disc, and 110 minutes on a dual layer (allowing for authoring overheads).

Encoding at around 5000 kbps with 192 kbps gets you around 3 and a half hours on a dual layer disc.

[lordsmurf]

The 6-hr speed seems roughly to the 6-hr VHS speed, maybe a little worse; viewable, but not great.

No. 6-hour on a VHS tape was still pretty close to a SP mode 2-hour, in terms of resolution and video signal. More grain, yes, but not bad. DVD tech is entirely different. A 6-hour encode throws away at least half of the video data, and it looks far worse than VHS ever did.

Personally, I can't see much quality loss from the 1-hr to the 2-hr recording time. The video looks a little poorer at the 3-hr speed, and maybe just a little worse than that at the 4-hr speed. If I thought I might want to save something I recorded to watch more than once, I wouldn't go lower than the 4-hour mode. I'd only use the 6-hr mode for some very long program or series of programs that I'd just watch once and then discard.

Not quite. Quality in extended modes are dependent on the machine hardware and firmware settings. A video encoded at 2 hours on a crappy encoder (Panasonic, some Cirrus) looks worse than 3-hour or even 4-hour on another machine that uses a good encoder with good settings (LSI chipset, amongst others, with 352x480 and a good bitrate allocation).

Modes mean zilch in the DVD world. It's something put on machines for consumers who are used to VHS tapes. But even then, the ONLY thing in common is running time, not quality. Not at all.

[PlayWithFire]

wow, thanks for all the replies, and so fast too
i'll stick to around the 2 hours mark then, thanks

and, happy thanksgiving everyone

[CobraPilot]

Lord Smurf makes some good "technical" additions/corrections/opinions to my post, but it probably still remains that "the eye of the beholder" is the final determinant.

You play with the "stuff" you have and decide how much quality degradation you can stand--if any--to put more on a disc.