Zip!!

[Glen]

is it possible to zip the files. like make them at least 30 % smaller........

this would be a great advantage for those who has very limited memory in their TI's!

[Jeffrey]

Well, not in .zip format, i do not think, however yes, i believe that in asm it would be possible to store program code into a small package of numerical data, and then recreate the program at a later time, sort of like WinZip. In BASIC there would be no way. I know very little about ASM, so I do believe it would be possible, but I am not sure. I wouldnt be the guy to do this either.

[David]

It is possible to do so. The algorithms that WinZip uses are named Huffman and Lempel-Ziv, and they are free for everyone to use. But it takes a computer genious to understand them and to implement them for calculator usage.

[Pascal]

You could do zip format on the calculator, but the ammount of space th algorithims take may outweight the memory the compression saves. Thats one of the bigger factors in 83+ compression routines. You could make a compressio routine that could compress any pic on the calculator to one byte. However, the ocmpression routine would be so big that it would probably take a few hundred K of mem or even a megabyte. You need to find a suitable balance. But certainly some altered form of the zip process could be emulated into the calculator. In many ways an forms, it already has.

[yugniht]

speaking of compression, even though this is off-topic, I heard about a new type, called mpeg 4 I think. If I remember right, mp3 compresses songs to 1/10th their normal size while mpeg 4 would compress them to 1/100th of their size. I think all of this is right, has anyone else heard or this?

[NETWizz]

Yeah, I heard about it while watching some Gadgets show on TV.

MP3 was also discussed as being created many years ago, but only available recently because the computational speed needed to decompress and play an MP3 on the fly was not met be early computers.

I remember playing my first MP3 about 5 years ago on a P2 266MHZ with 32 Megs SDRAM PC100 (yeah laugh)

It was almost a joke trying to play an MP3 because it would pause every once in a while trying to catch up and play it. With any other programs running, it did not work well at all.

Finally, I got a Pentium 3 @ 800MHZ and 128 SDRAM PC 133. MP3's finally worked.

Now, I have a Pentium 4 @ 2.83 and 256 DDR at work and the same 800 mhz piece of trash at home.

Next year, when we upgrade at work, I will take my PC with me instead of putting it in the trash.

[Arcane Wizard]

I don't know what was wrong with that P2 266mhz system but I've never had any troubles trying to listen to mp3's on my old P1 133mhz which had 48mb simm ram and an old soundblaster 16 soundcard.

I could even play Baldurs Gate 2 on it and listen to music at the same time, without any pauses or glitches (besides the occasional crash because my hd was corrupted and windows tried to write (swap file) to it anyway).

[gorchy]

Isn´t it possible to use something like RLE ( run length encoding ) ?
Whenever there are more than 3 bites inline, you could shorten it by setting a flag to show that the next 2 bytes are compressed code ( normally $FF ), secondly how often it should repeat and thirdly the byte to repeat.
it should look like this:
$8A ,$8A ,$8A ,$8A ,$8A
is compressed to:
$FF ,$05 ,$8A

Look also in "fate by fire", it´s better explained there

[NETWizz]

[NETWizz]

[Jeremiah Walgren]

This probably won't help much, but there's a library for a really old 89 shell (DoorsOS) that allowed you to "zip" the programs on your calculator. Perhaps finding the source and porting it might be worth doing. And if I remeber correctly, there's a program for the 86 on ticalc.org that also does compressions on-calculator. Perhaps porting that would work...

Anyway, there's my 2 cents.

[gorchy]

[NETWizz]

The DoorsOS routie was probably nothing more than RLE.

[Pascal]

Yea MP3 are quite interesting. see, in normal CD quality music, there is a very high sampling rate and a huge variety of frequenies, some are un audible ot the human ear becasue of their either high or low frequency. These items are deleted and as Jbirk said, some of them are combigned if they are in a clse enough proximity to eachother in wave form. A cd quality song is about 25 megabytes, however mp3 is only a bout 3 to 4 to you can imagine how much is compressed and removed from the sound track.

[Job the GameQuitter]

If I remember correctly Gemini used a form of compression for the levels based on patterns. Don't know how it worked though.

I also read that one of the compression tricks MP3's use is based on a "flaw" in the human hearing that results in us not hearing certain notes based on notes that we heard just before them.

Still on the topic of compression, my math teacher once told me a story of a dude who had developed a compression routine that was better than any other routine known so far, but who had held the techniques behind it secret, so no-one could steal them. He hadn't even written them down; all the routines were stored in his head (WEIRDO! )

When he had perfected them, he gave a tech-demo and promised he would sell/license (I'm not sure on the details here... memory... failing... ) the techniques soon.

The next day he was dead... and he hadn't written the techniques down...

The techniques weren't totally lost however (phew ), people have been trying to reverse-engineer them from the device he used for his techdemo. Whether they succeeded or not I do not know; the story my teacher told was pretty vague, I don't even know if it really happened or not.

(anyone else know this story, with more details? I'm quite curious if it's actually true, or that my teacher was just talking about some obscure sci-fi movie or something )

[NETWizz]

Yeah I heard some BS about that too, but never heard that anyone was killed.

Anyway, this seems to be nothing because nobody can truley perfect a compression algorithm in their head; therefore, the routines must be wrighten down somewhere. e.g. a .c file?

Now as for him being killed, that would be unlikely for the following reasons.

1. The idea was only in his head (no proof)
2. I seriously doubth WinZip, Stuffit, or WinRAR have hitmans on their payroll
3. Nobdoy kills someone with secret (useful as in $$$) knowledge; instead, they capture and tourture the individual until they have what they want; finally, after they have the algorithm, they kill the individual.

[Spyderbyte]