questionswhat is the quality of multiple movie dvd and blu…


the ones I've bought have each been on their own disc (ie 3 movies on 3 dvd's in a single case), so the quality hasn't been reduced to fit them onto a single dvd/BR.


@kamikazeken: Thanks. Not all of them are like that though. But it is good to know that the ones that are on individual discs are just fine.


I have a few DVDs where they used both sides of the disc (one movie on each side). The quality is the same as usual but you really have to be careful with the disc.

I have never seen one where they compress it down to fit multiple on a single side though. If this is what you mean there would have to be a huge quality difference.


DVD barely has enough capacity to hold a movie on one side of a dual-layer disc at a decent quality. A DVD holds roughly an hour per layer at good quality. They have to severely reduce the quality to fit more than one movie.

In some cases with less cared-about movies, they use the same severely reduced quality to make the standalone single movie DVD. I've bought some Ernest (Jim Varney) films where they were only a single layer DVD.

As for Blu-Ray, the capacity is much greater, but so is the desired quality. That's why when Ben-Hur was released on Blu-Ray, they put it on two discs. That was the only way to preserve the detail on those massive crowd shots. And it's only 212 minutes. That's 1 hour, 45 minutes per disc.

The Lord of the Rings movies are nearly as long (longer, if extended) and they only get one disc per movie, but again - there just aren't as many fine details that make encoding difficult.


All that said, if you'd watch it on VHS, a double-feature DVD is cheap and looks about as good.


@omnichad: Thank you . That's pretty much what I was wondering. So not really much of deal unless watching it on older type tv.


@omnichad: A DVD can hold about 3.5 hours of good quality footage. It's quite common for tv series to be released with 4 hour-long episodes per disc - that's about 45 minutes each without commercials, or about 3 hours total, plus a few dvd extras.


That holds well for sitcoms where there's a static background for a lot of the time. 3 hours on a dual layer DVD is 6.47Mbps. That's enough for passable HD if you're talking about MP4/H.264 (used by Blu-Ray). But if you're talking about cinematic drama or high-motion action movies, in MPEG-2 and AC3 audio, that's not much capacity.

For high-action scenes, you want to encode close to the maximum bitrate of 9.82 Mbps for a lot of the runtime. That gives you only 2 hours total to work with.

Putting 3 hours on a disc reduces the quality by a third - that's in hard numbers. And not even accounting for more than one audio language track.


I'm a bit confused, because you're taking about DVD and HD in the same sentence. I wouldn't expect HD quality on a DVD, I would expect a crisp, clean, 480p transfer for a commercially released DVD.

Sure, you could encode your own HD files and burn them to a DVD, and then you'd be very limited by the time constraints you mention, but that's not something you would find for sale in a typical store.

Am I missing something here?


@djp519: The only reason I mentioned Blu-Ray is that 6.47Mbps is a very high bitrate in Blu-Ray. It's several times that used by Netflix for the max quality HD streams. But since DVD only uses MPEG-2, it's not possible to pack as much quality into such a small space.


A single-layer DVD can comfortably fit a two-hour movie. The original DVD release of Dogma, for example, contained the 128-minute movie on a single-layered disc, and it looked fine.

Omnichad, you say that "putting 3 hours on a disc reduces the quality by a third" in "hard numbers," but you're confusing bitrate with quality--the relationship between the two is not linear. A three-hour movie on a dual-layered disc might have less bitrate to work with, but that difference will manifest itself as a virtually negligible difference in quality.


@cafink: Virtually negligible depends on the size of your TV. I just know that I wouldn't buy it - I've seen some bad ones in the past. However, I've seen just as many that are one movie on a single-layer disc - and there's no warning on the packaging that they went cheap. At least Blu-Ray usually lists the actual bitrate on the back cover.


Using a single-layered DVD for a two-hour movie is not "going cheap"; it's perfectly adequate and well beyond the point of diminishing returns for bitrate increases. Squeezing much more video than that per layer WILL adversely affect the video quality, but at two-hours-per-layer the compressed video is virtually indistinguishable from the source and there is no appreciable benefit to be gained from increasing the bitrate.


@cafink: Again, "virtually indistinguishable" might be true for someone viewing a 32" TV at 8 feet with below average vision. I own some movies that I will re-buy if they ever get a proper re-release because of compression artifacts that are just a little too annoying. These are all single-layer DVD's with 2 hour movies on them.

It does have a lot to do with how much motion there is. An action movie requires a lot more bandwidth than one that's mostly talking heads in front of relatively still backgrounds.


A few compression artifacts that are "just a little too annoying" is a far cry from a "sever reduction in quality," which is what you initially claimed would be the result of putting more than an hour of video per layer on a DVD.

A typical DVD release may contain visible compression artifacts, but that's as likely as not to be an issue with the specific encoding on that title, and not necessarily a given for the total bitrate.

Admittedly, just blindly doubling the disc space with a second layer means the disc author doesn't have to worry about bitrate as much, but your earlier posts made it sounds like single-layer discs for feature film were unusual and conspicuously poor in image quality, both of which are patently false. I don't think they're as common as they used to be, but double-sided discs with a single layer per side, and the complete movie on just one side (usually with a fullscreen version or special features on the reverse) was perfectly common.


@cafink: having compression artifacts that are visible at all from a distance is enough to make me not want it. I do think that it's rare to find a movie that has poor compression and doesn't also use a low bitrate.