How can you tell if a DVD has been compressed?

[Flav_cool]

Hi,

I'd like to know a way to detect and confirm whether a dvd has been compressed with something like dvd shrink because on most torrent sites they don't specify.

Thanks

[Alien5]

the ones on torrent sites are not compressed

[{I}{K}{E}]

the ones on torrent sites are not compressed

???

yes they are.

99,9% of all new DVD releases are DVD9.

[Darth Sushi]

You'll also notice that DVDs encoded with DVDShrink will have approximately the same file size (just shy of 4.5GB). This due to the target size setting in DVDShrink.

[3RA1N1AC]

You'll also notice that DVDs encoded with DVDShrink will have approximately the same file size (just shy of 4.5GB). This due to the target size setting in DVDShrink.
this MAY be achieved by deleting some of the extra features or re-compressing the menus/features though, so it doesn't necessarily tell you whether the movie itself has been re-compressed, unfortunately.

i'd guess that the only ways you can tell whether a movie's been re-compressed are:
1) the nfo file says so
2) you know that the original disc was much larger
or
3) you have a sharp eye and just know how to spot re-compressed video

[Gripper]

so if they fit a 4.7(dvd5) they may have been compressed or not,just had all the extras and crap cut out,and if they are larger(dvd9) they are untouched.
Wondering if the running time could be a factor,if its short,like 80mins it'd fit a 4.7 uncompressed and if it's a 120mins ti'd have to be compressed

[Master$hake]

depends on who ripped it, there is no way to tell. Unless you know the person that originally ripped the movie there is no way to tell unless you download it.

[Flav_cool]

Hmmm...ok I was thinking if it's over 120 min it was definetly ripped? (Since 4.7gb dvd is 120 min? ...but that would be at some sort of "standard" bitrate, but dvd's differ in bitrates right?)

[{I}{K}{E}]

Hmmm...ok I was thinking if it's over 120 min it was definetly ripped? (Since 4.7gb dvd is 120 min? ...but that would be at some sort of "standard" bitrate, but dvd's differ in bitrates right?)

that's incorrect. the time (120 min.) on a DVD is used when you create a music DVD.

[Darth Sushi]

That 120min is based on one and only one codec/format. If I use .wav on one cd and .mp3 on another, which do you think will have a longer playing time if both were exactly the same file size. Also, the bitrate will play a big roll on the size of the movie. I have 2 "Lawrence of Arabia" DVDs. Both have the same run-time yet the SuperBit version spans 2 DVDs.

[Flav_cool]

What would you guys say the "average" bitrate of retail dvds are? And I know it varies...but usually they are around _________ so that I know if a dvd i download has under this average or over.

[{I}{K}{E}]

What would you guys say the "average" bitrate of retail dvds are? And I know it varies...but usually they are around _________ so that I know if a dvd i download has under this average or over.

noone knows that. depends on runtime, menu size and how many extra's...

[Flav_cool]

I know but give me a let's say an average for a 2 hour movie...I don't need an exact number just and approximation like ~4000kbps, ~5000, ~6000, etc

[3RA1N1AC]

I know but give me a let's say an average for a 2 hour movie...I don't need an exact number just and approximation like ~4000kbps, ~5000, ~6000, etc
dual layer with no extras would prolly be close to the bitrate limit of 9000. like superbit editions and criterion collection two-disc sets (where disc 1 is just the movie and disc 2 is the extras).

single layer with no extras, or dual layer with a nice pile of extras... maybe around 5000-6000.

single layer with a bunch of extras... well, i think most video companies are wise enough not to attempt such a thing. 'cause once you get down near 3000 at full resolution (720x480. dvd-video supports lower resolutions but i don't think they're ever really used professionally.) the picture quality gets pretty ugly. 4000-5000 is about as low as you can go in most cases.

HOWEVER the estimates i gave are very very rough. as IKE said, the actual numbers on movie discs are all over the place. ideally for a full color, 90-120 minute movie, with a lot of movement, they usually want to keep it somewhere between 5000 and 9000. but you know, it varies by content. black & white movies (color data counts for a large part of the bitrate), cartoons that don't have a lot of visual detail, tv shows like sitcoms where people mainly stand around & talk instead of running & blowing sh1t up... that's the kind of stuff where they can get away with using relatively low bitrates.

[Flav_cool]

Cool man thanks, very informative and exactly what I was looking for!

Now the only thing I've never understood is how more bits gives better quality. Like kbps refers to kilobits per second for every pixel added up right?

What does assigining more bits to a pixel do?

I used to think that what mattered was resolution and I obviously know that this is wrong but I don't quite see why.