Why does PGP format takes up so much space?

[Jeffry]

Just out of curiosity,

Why does Sony's PGP format take a lot of space when you can get the same quality with JPEG? Memory Stick scheme perhaps?

[AlbertLu]

One word - speed.

[rldunn]

JPG is a compressed format, while PGP is not. That's why PGP files display so fast, because the processor doesn't have to uncompress them first, while JPG files load painfully slow on 33 and 66 MHz processors and even take a second or so on the NX.

[Shogmaster]

I think that's wrong. I think PGP is compressed. It's just that the compression is very low.

The speed difference IMO comes from the fact that the PGP files are stored on the RAM, and the JPGs are on the stick, so naturally is MUCH slower. And also keep in mind that opening the same JPG is much slower on the SJ series than the T615 (both has 33Mhz DB). That points to the memory stick IO speeds being the main factor in difference in speed when opening JPGs.

[DanT]

I have N760C and use CrsImageViewer to view a 41KB .jpg image in MS and it takes about 5 seconds. I also have 152KB .prc image in MS that can be viewed by PGPocket in less than a second. Explain that.

[Spiral]

because the prc isn't compressed much, it can just be copied to ram (which can be done fairly quickly)

[jaydisc]

Both PGP and JPEG can be loaded from the card and the difference is quite noticeable. On OS 5 devices, JPEG can be stored in internal RAM and once again, the difference in speed is quite noticeable. I agree with AlbertLu.

[Shogmaster]

I know for a fact that the PGP files can be compressed because it gives you that option when you convert images via Picture Gear Lite 4.4 that's still on one of my computers.

Anyways, I don't know if this info is gonna clear up or confuse the matter more, but I took a 39KB 320x320 JPEG image and turned it into a PGP file (options: 320x320, 16 bit color, compressed) and it balooned into a 195KB monster. (Obviously the compression available for PGP format is very inefficient! ;) ) I then put both of those on a memory stick, and read them through AcidImage on my NX.

The PGP verison took about 2 seconds to open, while the JPG one took about half a second. Seems like to me that going purely on the file size, the relationship is about right (4 times bigger file took 4 times longer to open). And then when I moved the same PGP file into the internal RAM from the memory stick via Clie files, the file took smidgen less then a second to open (which would seem to back up my theory).

I couldn't figure out how to move JPGs into internal RAM, so I just opened an existing JPG that came on the NX in the ROM/RAM (the girl with baloons pic) even though the size of the file is nothing close to the PGP file. The girl JPG (320x450, 58KB) took about one and a half second to open.

The smaller (in KB) yet bigger (in pixel dimensions) JPG file in the RAM took longer than the bigger (in KB) but smaller (in pixel dimensions) PGP file. I guess the PGP files are compressed at a very low level, which helps with speed in opening the files just like you guys are saying.......... BUT...........check this out: That baloon girl JPG file in the internal RAM, which took 1.5 seconds to open, when copied to the memory stick (I used the Clie Viewer for this function because I couldn't located the JPG in the RAM through Clie Files) opens up in about half of a second!!! And it's still the same 58KB in size!!! :confused: :eek: :confused: :eek: :confused:

My brain is now mush. Anyone care to explain this rather curious phenomenon?

[Unregistered]

or it could be that acidimage has much better and more efficient jpeg decompression code (asm?) than it does for PGP decompression

[Shogmaster]

But how's that explain JPGs opening faster in external flash card than in the RAM? Something is definitely weird here.

[AlbertLu]

There is a possibility that the internal memory read/write speed is affecting the overall perfomance speed.

A simple (exaggerated you might say) example: You have a big pgp file (say 500k), after conversion to jpg the file size become significantly smaller (say 50k).

If the memory read/write speed is fast, everything perform as expected - jpg file load/decode faster.

If the memory read/write speed is slow, you may end up having pgp file read faster than the jpg file, because the pgp file required less memory read/write activity (less decoding), while the jpg file required more intensive memory activities.

Confused? So am ;)

This used to be one of the typical trade-off scenarios back in the days of Windows 3.1x or 95 when compressed disk are somewhat popular.

[yorrick]

AcidImage decompression is a lot more efficient than PCP viewer.
AlbertLu is correct - that PGP is an image format that uses compression like JPG. However, the image is not compressed by much in terms of size. The smaller file size is when you convert/compress the image to a lower quality image - ie. more information is lost and there is a lot more artifacts and pixellation.
This occurs on JPG format -but JPG is optimised for size and relies on the application to decompress it whilst PGP does not rely as much on the application to decompress.