Why do I want iso over mp4/mkv/etc

[Sento-kun]

Yes, i'm a super newb at this.
every once in a while i download an iso because i can't find anything else. i mount it on poweriso and play it through vlc. i keep reading that an iso is the purest quality you can get from the original dvd but all my iso movies seem to be somewhat pixelated compared to the 1080p stuff i download. am i supposed to be doing something else to this iso or is it my laptop being crappy or.. uzzled:

thanks..

 

[Desu]

DVD resolution can't go over 480p (or 576? i'm not sure); that's why you're seeing that much difference when you compare them to videos shoot in HD

 

[BudEWiser]

You really only need the ISO if you plan to encode them yourself, or you can't find another version. To get 1080p stuff, you would have to get the huge BDISO.
The reason that some of them appear crappy is that they are almost always interlaced videos, and all of the deinterlace options in VLC suck quite bad.

 

[SamKook]

Another reason they might look bad is that they are often recompressed to fit on a DVD5 instead of a DVD9. I've seen ISO compressed that way that were worst than the usual xvid rip.

The reason you want an untouched copy of an ISO over a mp4/mkv/etc is that the ISO is a perfect copy of the original DVD so you get the exact same quality.
Same for a BDISO which is a perfect copy of the original bluray video.

There's a few mp4/mkv that can be better than the original if they were deinterlaced(since almost all JAV is interlaced) with a high quality deinterlacer since it would be too slow to do it in real time(for now at least). Most if not all 60fps rip on this website are of very high quality and worth considering over the ISO.

I started to get ISO's whenever I can because I can't stand all the poor quality rip we see everywhere anymore. Especially since all those wmv started popping out that are almost as huge as ISO's, but have the quality of a bad avi most of the time.

 

[Sento-kun]

okay, i was worried about this - the answers are a bit over my head i think haha
so is it the fault of the original ripper or is the work now up to me? do i just leave this as is? should i turn it into an mp4 or something?.. thanks again..

 

[SamKook]

It all depends on what you want and how much disk space you're willing to use on them.

An ISO(whether it's from a DVD or a BluRay) is the best quality you can get(with a few exceptions, but I'm omitting them to keep things simple).
Their downside is that they take the most space of all the video formats.

Mkv/mp4 are usually encoded with a good codec so they usually have decent quality and a medium filesize.

Avi/rm/flv are usually of very low quality, but they don't use up a lot of disk space.

Wmv vary from very good to terrible quality, usually take a lot of space and is the least well supported by video players so they're often not very attractive to get.

For all those different formats, the person who rip them can do an absolutely horrible job, a really good one or anywhere between the two. But in most cases, what I said above should be true.

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A few other tips:

Usually, the higher the resolution is, the better quality the video will be, regardless of the format it's in.
The most common for rips are ~400p, 480p(like the original DVD), 720p and 1080p(like the original BluRay)

Some posters will make rips of high quality and others will do some of poor quality so remember who has good quality posts and always download from them if possible.
With JAV, it's pretty much always of low to decent quality, but for idols, there's a lot of high quality posters(look for the 60fps rips).

You would be better off using a video player that supports direcshow(which means not VLC) when you watch ISO's(or any other videos) since they offer higher quality deinterlacing and more control over the quality.
LAVfilters offers yadiff deinterlacing which is pretty good and you can even deinterlace at 60fps which means better video fluidity.
It might be a bit more complicated to set those up, but there are a lot of tutorials about it(a google search for "MadVR + Lav Filters" will bring up a lot of them).
If the tutorials are still too complicated, I think the CCCP codec pack has some pretty good settings out of the box so it's worth a try.

I hope I made things simple enough.

To answer your questions a bit more directly:
It's most likely the rippers fault if the quality is bad(sometimes the studio that made the DVD hasn't done a very good job as well). The only thing you can try to make it better is a better deinterlacer, but that may or may not help.
There's not much you can do(other than maybe better deinterlacing) to make it better so leave it as is or try to find a better version.
Only turn it into a mp4 or something if you think it takes too much space.