(05-31-2017, 11:13 AM)Kurausukun Wrote: [ -> ]This functionality is usually not needed by Wiis because most people keep theirs updated, and it's especially not really needed by Dolphin, but it's definitely removing data that cannot be recreated, hence why it is indeed "lossy." I'm not sure if it also skips other partitions, like Brawl's masterpieces for example, but the update partition alone is enough to make it a very lossy process which will fail any checksum tests to make sure you have a good game rip.
Okay, I get what you're saying... there's no real analysis required... it's leaving out partitions that don't contain the game itself.
(05-31-2017, 11:13 AM)Kurausukun Wrote: [ -> ]It's a knife right in the heart of data integrity. Please don't argue that this is not a lossy scheme or try to redefine "lossy," because it is already a well-defined black-and-white term. I'm in a data science major; I do, at least to some degree, know what I'm talking about.
Spare me the dramatic metaphors.
I have a masters in computer science, and have been working in the field for 11 years. MP3 encoding is lossy. H.264 is lossy. JPEG is lossy. This is because the critical data you want to listen to or see has been changed and does not sound or look the same, even if it sounds or looks very similar.
Leaving out a chunk of data
that is not required for the program to function is not "lossy." The apt analogy would be that you write a "hello world" program and discard the vast majority of the libraries available in your development environment because they aren't required to make "hello world" work. That doesn't make your project "lossy."
It is lossy because it is not a 1-to-1 copy of the game disc, so the original game file can not be recovered from the rip, which is the definition of what lossy is, in case anyone doesn't know off the top of their head.
Verifying a scrubbed game dump to see if you have a good dump of the game against the md5 sum of a proper disk dump will say you don't have a good dump. And since you're not getting a 1-to-1 disk copy, games could behave weird since data blocks are not in the place they're expected to be.
An example off the top of my head is accurate disk timings. Based on where the data is stored on a disk affects how fast it loads, aka farther in towards the center loads slower than data located farther out closer to the edge. There are a lot of games that rely on data being accessed exactly as fast as it was designed to be, and if you read through some of the old Dolphin monthly updates you'll find some examples. So if you have a stripped down disk image file, data could not be where it's expected to be, causing loading issues. I know a game that suffers from this is the Metroid series.
https://dolphin-emu.org/blog/2017/03/01/dolphin-progress-report-february-2017/#50-2431-dvd-timing-accuracy-upgrades-by-mmastrac-and-josjuice
Dolphin on the other hand, once you verify you have a good game dump, can compress the game. Haven't used in in a while because I already compressed all the games I needed to, but from what I remember it doesn't actually discard any data, so it's considered lossless, and I need to verify but I'm pretty sure you can uncompress them back to the original file.
About the lossy or not lossy thing: I would definitely call USB Loader GX's ripping lossy. Calling it lossy
compression feels a bit odd, though – it's just flat-out discarding data without anything clever going on. Though in one sense, I suppose it still does make sense to call it compression.
(05-31-2017, 02:48 PM)KHg8m3r Wrote: [ -> ]And since you're not getting a 1-to-1 disk copy, games could behave weird since data blocks are not in the place they're expected to be.
An example off the top of my head is accurate disk timings. Based on where the data is stored on a disk affects how fast it loads, aka farther in towards the center loads slower than data located farther out closer to the edge.
Does USB Loader GX actually move data blocks? That shouldn't be necessary, since the WBFS format allows you to leave out blocks without rearranging other blocks. (It does rip to WFBS, right? I've never tried ripping with it myself.)
(05-31-2017, 02:48 PM)KHg8m3r Wrote: [ -> ]There are a lot of games that rely on data being accessed exactly as fast as it was designed to be, and if you read through some of the old Dolphin monthly updates you'll find some examples. So if you have a stripped down disk image file, data could not be where it's expected to be, causing loading issues. I know a game that suffers from this is the Metroid series.
https://dolphin-emu.org/blog/2017/03/01/dolphin-progress-report-february-2017/#50-2431-dvd-timing-accuracy-upgrades-by-mmastrac-and-josjuice
Pretty much all games are fine with the minor differences you get from data being in a different part of the disc, though.
The Metroid Prime games don't have any issues caused by incorrect loading time emulation as far as I know. It's just that speedrunners and others care a lot about having the correct loading times because of how the loading times affect gameplay.
(05-31-2017, 02:48 PM)KHg8m3r Wrote: [ -> ]Dolphin on the other hand, once you verify you have a good game dump, can compress the game. Haven't used in in a while because I already compressed all the games I needed to, but from what I remember it doesn't actually discard any data, so it's considered lossless, and I need to verify but I'm pretty sure you can uncompress them back to the original file.
Dolphin's compression feature is lossy when used with Wii discs (though IIRC it just discards data that isn't part of any file without discarding things like the update partition). It is however lossless for GC discs. It's done this way because Wii discs compress very badly with generic lossless algorithms (GCZ uses deflate) because the data is encrypted.
Okay, I get it. It's not a 1:1 copy of the disc, so we're calling it lossy. I find that to be a very broad and vague definition for "lossy," which is more commonly used for algorithms that *modify* data, rather than discarding unused pieces while leaving other pieces unmodified. But I understand the way it's being used here.
For what it's worth, my entire library of Wii and GameCube games was ripped with USB Loader GX, and they all work without issue both on my hacked Wii and in Dolphin.
I'll drop the subject now, because it's apparent this is only of interest to me and has nothing to do with the OP's question.
Edited to answer JosJuice's question: Yes, USB Loader GX rips to WBFS.
about how much space do you save on a typical disk using software that we can all agree modifies the original. Depending on how I store my games this might be important later on down the road
(05-31-2017, 11:13 PM)jachin99 Wrote: [ -> ]about how much space do you save on a typical disk using software that we can all agree modifies the original. Depending on how I store my games this might be important later on down the road
It depends a lot on the game. It can be anything from a few hundred megabytes to four gigabytes or so. I would guess many games are in the middle of that range.
With my game library, using Dolphin's built-in GCZ compression, my smallest game goes to 187 MB, whereas my largest is nearly the same size as the original. The average is 2.57 GB, but your experience may vary, and potentially quite wildly, as there's such a large variance.