38 votes
Accepted

How did the Sega CD decompress video?

We used to have to write our own video playback system, so each game did it differently. I worked on Microcosm for the SegaCD and if I recall we used a 16 colour palette for the video playback and had ...
34 votes
Accepted

Why does MP3 audio decoding overwhelm retro CPU's?

What's lacking is mostly raw number-crunching ability. The MP3 format is relatively lightweight, and can be implemented using only fixed-point math (no FPU required), but it still takes a fair amount ...
  • 8,452
28 votes

How well known and how commonly used was Huffman coding in 1979?

According to Google Scholar, Huffman’s 1952 paper had 326 citations by 1979, which given the volume of publication at the time means it was well-known, as far as can be determined now. Most ...
  • 98.3k
25 votes
Accepted

How well known and how commonly used was Huffman coding in 1979?

Well, in fact, a closely related question has been asked (and answered) few years ago: What is the history of data compression tools on personal computers? From that question, and its answer, it ...
  • 3,842
18 votes

How did the Sega CD decompress video?

Playback of compressed digital video is handled entirely in software on the Sega CD which is why FMV games on it play with the video taking less than the full screen and at relatively low frames per ...
  • 4,092
17 votes
Accepted

How to convert Amiga DMS to ADF?

From some quick research, WinUAE (a popular Amiga emulator) supports reading a DMS file just like an ADF. So you could probably mount it and then save it back as ADF. Also, according to the ADF Opus ...
  • 2,853
16 votes
Accepted

Compression techniques used in old ZX Spectrum tapes

I don't recall any mass-market commercial software for the Spectrum using the term "decrunching" - I'd associate that more with the demo and cracking scenes of central and eastern Europe, ...
  • 926
13 votes

How well known and how commonly used was Huffman coding in 1979?

If you actually look at how the Z-Machine compresses texts, it does the following (from memory, it's been a while): There's a list of frequently appearing words (like "the", "and") which are directly ...
  • 22.1k
13 votes
Accepted

Could early nineties PCs access raw CD bitstream?

TL;DR; Yes and yes, but. CD-ROM Mode 2 offers all 2336 bytes of a CD-ROM block for user data. By default all CD-ROM drives can read Mode 2 disks as well Mode 2 CD-ROM have been produced, but it never ...
  • 178k
12 votes

Why does MP3 audio decoding overwhelm retro CPU's?

Mp3 is primarily a lossy compression format for audio. It must be decompressed, and the process needs a lot of CPU time (as for retro computers.) Modern computers both have speeds good two orders of ...
  • 6,675
10 votes

Was there a compression program based on the Mayne-James algorithm?

After browsing the paper, it looks like the idea is to extract common sequences of letters from a given text into a table of a certain size, and then replace those substrings with references to the ...
  • 22.1k
10 votes
Accepted

What is the history of data compression tools on personal computers?

The story is told in this 1988 usenet post by Paul Homchick: Some time went by and it was a CP/M world, and diskettes were bigger. In 1981 Richard Greenlaw released SQ and USQ, based on Huffman ...
9 votes

Why does MP3 audio decoding overwhelm retro CPU's?

Like others already answered: old CPUs does not have enough MIPS, and/or they are lacking instructions that would helped in MP3 decoding algorithm (remember that MP3 is standardized in 1995.). Nice ...
9 votes

What is the difference between DriveSpace and DoubleSpace?

It appears that there are several versions of both DoubleSpace and DriveSpace. Information about each version as I find get it will be posted in this answer. DoubleSpace DoubleSpace uses MRCI, which ...
  • 17.8k
9 votes

Compression techniques used in old ZX Spectrum tapes

As far as I know, there were two main approaches to compress the data. The first one, more common, was to load the whole code and "de-crunch" it. It uses RLE or simple vocabulary algorithm (...
  • 5,172
8 votes

Compression techniques used in old ZX Spectrum tapes

I wrote the compression routine use by the Multiface on the Spectrum and Amstrad machines. It was a plug in unit that would save all memory to tape and allow you to continue your game where you left ...
8 votes
Accepted

What was the first database to start compressing in situ?

As time goes by, CPU power becomes cheaper and more plentiful, to the point where it makes sense to start spending some of it using more complex storage formats that save disk space and bandwidth, and ...
  • 178k
8 votes

What is the difference between DriveSpace and DoubleSpace?

MS-DOS 6.0 and 6.20 shipped with DoubleSpace. MS-DOS 6.21 removed it due to the Stac lawsuit, and MS-DOS 6.22 replaced it with DriveSpace with an incompatible algorithm and format. Soon after MS-DOS 6....
8 votes

Why does MP3 audio decoding overwhelm retro CPU's?

Early 68k processors implemented a multi-cycle multiply instruction (70 cycles per MULx), so the inverse MDCT would likely be the limiting factor in terms of raw CPU time.
  • 7,834
7 votes

Could early nineties PCs access raw CD bitstream?

I think your premise is a bit off. Compression (lossy or otherwise) makes media much more susceptible to errors, not less. If you flip one bit in an uncompressed image, the probable result is that one ...
  • 3,966
6 votes

How well known and how commonly used was Huffman coding in 1979?

(This is not really a great question, as it's asking for speculation about knowledgeand decisions of people long ago, something rarely supportable by referencee) It might be helpful to look into ...
  • 178k
5 votes

How well known and how commonly used was Huffman coding in 1979?

In 1971 I took an information theory freshman seminar at MIT which included Huffman coding. Huffman coding was well known and casually taught as something that was widely used, but as it was one of ...
  • 667
5 votes

How do I interpret these instructions for decompressing game data?

Those codes have nothing to do with the CPU instructions. You write the program that interprets the compressed data according to the given rules to decompress it. The # is the bits marked with x in ...
  • 19.7k
3 votes
Accepted

Reconstructing uncompressed program from compressed tape image

With Vice, you can wait until the uncompressed, actual, application code has started execution, then activate the built-in ML Monitor. You will thus pause execution at wherever the Program Counter ...
  • 57.6k
3 votes

Can't install El-Fish on MS-DOS 6.22

I haven’t tried VirtualBox for this, but DOSBox runs the installer fine: copy all the files on the installation disks to a single installation directory, e.g. ELINST (in a temporary directory) — you’...
  • 98.3k
2 votes

How to convert Amiga DMS to ADF?

The Disk Masher System entry on the Archive Team wiki suggests the following tools: xDMS (Public Domain, portable C source) dms111 (Original Amiga software) Ancient Format Decompressor (decompresses ...
  • 4,933
2 votes

Compression techniques used in old ZX Spectrum tapes

For what it's worth, "decrunching" (and the opposite, crunching) appears to be a relatively common slang term for decompression on load on from the time when these systems were popular and ...
2 votes
Accepted

How do I interpret these instructions for decompressing game data?

I understand each of these rows to be sequential instructions. Exactly, they are description (opcodes and data structure) for the virtual machine which is the decoder. What am I missing though to ...
  • 178k
1 vote

How do I interpret these instructions for decompressing game data?

What am I missing though to translate this into pseudocode that a non-"old school" programmer like myself can understand? It's hard to say what you're missing. It certainly doesn't seem to require ...
  • 1,409

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