Compressed VS Not Compressed?

[zombie2k]

Recently I saw an article where a rep stated that Resistance: Fall of Man was at the moment 22 gigs on a Blu ray disc. I was always under the impression that uncompressed = no quality loss and less loading because the data does not need to be decompressed.

However, some have pointed out, on numerous forums, that the RAM in the PlayStation 3 may make the loading times longer. Im no extreme techno guru like I assume most people here are...I generally only know enough to get myself by with upgrading my hardware/not blowing my PC up.

I think the idea of Blu ray for video games and whether or not Sony's decision to include a BR drive rather than DVD9 (like Microsoft) stands on whether or not compression makes a difference. What do you guys think, is not having to compress your game good, bad, or does it even matter?

 

[Platon]

Uncompressed textures on the disc is a baaaaad idea. It would take for ever to load them, it takes less time to load a compressed texture and uncompres it than load a non compressed texture. What you could have though is different levels of compression...

 

[ERP]

General rule of thumb id that uncompressing something is MUCH faster than loading it.

 

[nAo]

What do you guys think, is not having to compress your game good, bad, or does it even matter?

There pros and cons.
First of fall we must make a distinction between lossy and non lossy compression:
in the first case even though high compression ratios might be achieved quality can be compromised, in the second case quality is never compromised (at compression ratios disadvantage).
So even though Insomniac has decided to not use any lossy compression algorithm to compress audio they might have decided to use a lossless compression algorithm thus enabling faster loading times without degrading audio quality.
The same approach can be applie to other data such as textures, geometry, code, etc..
so it's still possible to greatly ameliorate loading times without compromising data integrity/quality

marco

 

[Graham]

With a 2x bluray drive, you get around about 9Mb/s read speed. (correct me if I'm wrong).
The PS3 offers up approximately 416mb of usable memory (if we are to believe the OS reserves 96mb). If we assume 2/3 of that is used for texture storage, you can work out some numbers.

So.
filling 278mb..

Raw, uncompressed, at 9Mb/sec (theoretical max), you have 31 seconds for textures alone. Needless to say, this is totally unacceptable.
Your looking at 42 minutes loading time for all the information on the entire disk (22gb)

As far as I'm aware, the PS3 bluray drive actually has higher potential read speed when reading a standard DVD (8x), however this is only at the edge of the disk (where most data is stored). The 360 has a 12x dvd, which maxes out at 17Mb/s at the edge of the disk. Bluray on the other hand reads at a constant speed at all points on the disk (CLV vs CAV).

 

[Bad_Boy]

But the hard drive plays no factor in load times Graham?

 

[Mmmkay]

I don't think anyone should be under the pretense that this is going to be 22GB of unique data. Aside from the duplicated content from multiple regional variations on the same disc, I imagine quite a lot of that content will be redundant data to reduce seek times on streaming.

 

[ShootMyMonkey]

With things like textures and audio, it generally all has to sit in memory when used, so you're bound to prefer compressed formats whether the disc can hold it all or not. Unless you've got so much memory that you don't know what to do with it all, and I've never heard of such a thing existing anywhere in the computing world (you can contrive some trivial case, but they will inherently be silly). It's a rather miguided notion among the public that Bluray invariably means less compression.

There are basically only three ways that lack of compression is a win for some unit of data -- 1. the quality is of high importance for some reason : this is sometimes the case for instance, when an image isn't just a picture or texture but has some numerical meaning. 2. The compression scheme you need to make things work is excessively complex and is extremely slow or high latency to decode for the given architecture : A good example of this is how a lot of uncompressed audio was used on PS2 titles. 3. The storage medium is so fast that compressed or uncompressed doesn't make much difference : I don't know if this has ever really been true or ever will be.

Lossless compression is still a potential win, but it depends on the type of data and how complex the codec is. It's possible to losslessly compress generic data a lot better than LZ77, but the increase in complexity needed to get a minor gain is pretty massive. So with things like losslessly compressing textures or audio, it's preferable to use something specialized for the task.

But the hard drive plays no factor in load times Graham?

You still have to get data to the hard drive. The hard drive only affects subsequent loads -- won't do much for the initial load times.

 

[Bad_Boy]

You still have to get data to the hard drive. The hard drive only affects subsequent loads -- won't do much for the initial load times.

It still plays a factor, no?
Anyways, IIRC the game loads while the cut-scenes are playing, and when the cut-scene is over it seamlessly goes into the gameplay. It's in the PSM article, I believe.

 

[zed]

compression is good
eg 256x256 uncompressed texture vs 512x512 texture (using dxt5)
both take up the same amount of memory , though the 512x512 might have some artifacts its still gonna look better overall due to the increased resolution
also what ShootMyMonkey said

 

[Inane_Dork]

But the hard drive plays no factor in load times Graham?

It will affect load times as much as it did for the Xbox.

So that means load times are still primarily dependent on the developer, not the hardware.

 

[Graham]

But the hard drive plays no factor in load times Graham?

I'd also expect sony have put limits on how much space developers can use for cache. (anyone know hard numbers?)
It wouldn't be much more than 256mb I'd imagine.

 

[Rolf N]

But the hard drive plays no factor in load times Graham?

Copying 512MB of "important" data to the HDD so that it can be loaded faster than from the optical drive will take even more time than just loading it directly into RAM, off the optical. We're talking some 50 seconds here, so it is significant. You can't do that all the time while the game is running.

This only makes sense for certain "core assets" that are needed basically everywhere in the game. Not for a room that you run past and never see again, and neither for a minute of dialog audio that plays exactly once.

(there may be situations where a prefetch (+optional decompression) to HDD is warranted, so that when the data is needed the optical drive is already free to read something else)

 

[Bad_Boy]

I'd also expect sony have put limits on how much space developers can use for cache. (anyone know hard numbers?)
It wouldn't be much more than 256mb I'd imagine.

Thats all speculation for now, I don't think anyone knows the limits except developers.

Still, your numbers completely ignore the fact of a hard drive. It's not like it's not standard and developers won't program for it. Why wouldnt they? Didnt kutaragi say back at GDC that "all developers should program with the HDD in mind"?

In the 22GB, they dont tell you how many repeated materials will be put on the disc (which would be a big factor in determining if 22gb is all orginal content). How many lanugages are on the disc (obviously if your're playing one language you wont use the rest of them, so why load them?)

I think its pretty much a lot of speculation on your part to say that the game will have 40+ minutes of loading. And even then, if it were a lot of loading, would you notice it all? Like I said above the cutscenes go seamlessly into the gameplay. This is insomniac we are talking about, I doubt they will kill the game with minute long loading times. Of course thats speculation on my part. But hell, we dont even know how long the game is.

Anyways...
I'm sure we will find out more in november.

 

[V3]

I'd also expect sony have put limits on how much space developers can use for cache. (anyone know hard numbers?)
It wouldn't be much more than 256mb I'd imagine.

With the Jp PS2, games like FFX can be installed to the hdd. It takes like 10+ minute to install the game. I wonder if you can do the same with PS3. Any devs able to give some detail ? Installing 20GB worth of data going to take forever with PS3 slow 2x BR Drive.

On side note I thought the BR standard required 4x speed for certain part, does that mean PS3 won't support it ?

 

[Rolf N]

On side note I thought the BR standard required 4x speed for certain part, does that mean PS3 won't support it ?

BR video requires a transfer rate of 54mbps sustained over the entire disc. That means that a 2xCAV drive wouldn't play BluRay video. A 2x drive must be CLV.

A 4x CAV drive would work, too. It just hasn't specifically been announced that the PS3 will have such a thing. However, wrt to your question, no, 4x speed isn't required for BR at all.

http://en.wikipedia.org/wiki/Constant_Angular_Velocity
http://en.wikipedia.org/wiki/Constant_linear_velocity
http://www.blu-ray.com/faq/#bluray_speed
Common PC drives are CAV, as is the 360 drive. Most burners support CLV modes for writing. The PS3 drive is currently believed to be 2xCLV.

 

[see colon]

With the Jp PS2, games like FFX can be installed to the hdd. It takes like 10+ minute to install the game. I wonder if you can do the same with PS3. Any devs able to give some detail ? Installing 20GB worth of data going to take forever with PS3 slow 2x BR Drive.

On side note I thought the BR standard required 4x speed for certain part, does that mean PS3 won't support it ?

10 minutes? it took me the better part of an hour (40-50 minutes IIRC) to install each of the resident evil: outbreaks to my PS2 HDD, and it halved the loading time durring play. but, those titles took about 90 seconds or so to load a room, so the 45sec wait was still pretty cumbersome.

the hard drive isn't some magic device that's going to make loading disapear. sure, it can speed things up here and there, but you still need to get data from the optical disc to the hard disk in order for it to work, so you still have loading. compressing the data on the optical disc would still be the better choice because you're always limited buy the speed of the drive.

 

[Danalys]

isn't it all done via streaming nowerdays. so what's the difference between streaming from a blueray to a hard disk or not with or without compression, and streaming from a DVD only with compression. on a blue ray they could put the whole thing in both compressed and uncompressed forms, and use which ever is better case by case.

 

[Powderkeg]

BR video requires a transfer rate of 54mbps sustained over the entire disc. That means that a 2xCAV drive wouldn't play BluRay video. A 2x drive must be CLV.

A 4x CAV drive would work, too. It just hasn't specifically been announced that the PS3 will have such a thing.

According to the PS3 specs on Sony's web site it is a 2X drive.

 

[see colon]

isn't it all done via streaming nowerdays. so what's the difference between streaming from a blueray to a hard disk or not with or without compression, and streaming from a DVD only with compression. on a blue ray they could put the whole thing in both compressed and uncompressed forms, and use which ever is better case by case.

compressed data will be better as long as you have CPU cycles to spare (for decompression). in the case of PS3, where you have this ridiculously multi-threaded CPU, you could easily reserve a thread or two for decompression. as far as textures go there are very few cases that you wouldn't want to have them compressed in some format that the GPU can use natively anyway.