In my opinion the biggest advantage of the various types of adaptive differential pulse code modulation techniques is their relatively low complexity overhead compared to normal linear PCM or companded PCM.
Typical variants allow you to save 50% space with relatively small quality loss.
The IMA variant is specifically optimized for simplicity. Other variants would trade some of the simplicity for improved quality.
Later audio compression techniques will typically achieve much better quality, but only with a computational complexity that typically requires hardware acceleration at their respective time of introduction.

You can find some more info on ADPCM in this thread: Compressed digital soundformats

IMO, it's only important if the few games that absolutely need it (like Duke Nukem 2) are among your favorites. And even for such games, there are usually workarounds. Other than that, you probably won't even notice that it's missing.

Well, the ESS ES1688 (particularly the non-PNP version, which is my favorite) and the ES186x (*the high quality cards) are the best of both worlds: they have excellent sound and are also extremely compatible - not just because they support ADPCM, but after years of using them, I've found them to be extremely reliable and less speed sensitive than... basically any other cards that I came across.

Now, do I care about ADPCM in particular? Not at all, not a big fan of Duke Nukem 2 (which is the only ADPCM game that I know of, anyway).
Having said that, I'm also a fan of the Yamaha YMF71x / 7x4 cards, particularly the YMF7x4 PCI, which for me has always been more compatible than the Yamaha ISA cards (*when used in DDMA or SB-Link mode). They are excellent cards, however, they're more speed sensitive than the ESS Audiodrive, that's for sure.

bloodem wrote on 2020-12-26, 16:33:

Having said that, I'm also a fan of the Yamaha YMF71x / 7x4 cards, particularly the YMF7x4 PCI, which for me has always been more compatible than the Yamaha ISA cards (*when used in DDMA or SB-Link mode). They are excellent cards, however, they're more speed sensitive than the ESS Audiodrive, that's for sure.

Sound quality on Yamaha 7x4 PCI cards are second to none, i am however baffled with the compatibility statement. Can you tell me which games you've had problems with the YMF 71x ISA cards?

Also can you try an AIL Miles driver game with the Yamaha 7x4 cards and check if it crashes? I suggest to try Dune 2 with Sound Blaster Pro digital sound.

I also like ESS cards, never had any issues with 1868 or 1869 cards, and i very much like the ESFM which is kind of a OPL3 superset.

ADPCM is only present in only 4 games i know of, and i'm not to worried about it since i don't like them to much:

- Duke Nukem 2
- Major Stryker
- Monster Bash
- The Last Eichoff

ADPCM importance is kind of overrated IMO, specially when even the most popular game of the bunch, Duke Nukem 2, has a nice patch with the decompressed files back to 8 bits, which makes all the sounds play fine on non compliant ADPCM cards.

Yamaha YMF-71X actually only support 8-4 ADPCM, it states so in the datasheet. Crystal chips additionally support the 8-2 ADPCM and ESS and ALS actually also support the 8-3 ADPCM mode (also known as 2.6 bit, doesn't make any sense to me).

So for me the best compromise between compatibility and Sound quality is the most important for me. My favorite chipset, after all these years is still the Yamaha YMF-71x, but i'd be happy with ESS and my favorite card right now is the Orpheus which is actually Crystal CS4237 based.

carlostex wrote on 2020-12-26, 18:10:

Yamaha YMF-71X actually only support 8-4 ADPCM, it states so in the datasheet. Crystal chips additionally support the 8-2 ADPCM and ESS and ALS actually also support the 8-3 ADPCM mode (also known as 2.6 bit, doesn't make any sense to me).

The "2.6 bit" makes some sense: You call this mode "8-3 ADPCM" (first time i heard this name, usually I hear 2.6bit or 1:3). It packs 3 samples into 8 bits (I suppose, that's what you intend to express with 8-3). If 3 samples need 8 bits, the average number of bits stored per sample is 8/3 bits, which is approximately 2.6 bits per sample.

carlostex wrote on 2020-12-26, 18:10:

Sound quality on Yamaha 7x4 PCI cards are second to none, i am however baffled with the compatibility statement. Can you tell me which games you've had problems with the YMF 71x ISA cards?

As an example, Prehistorik 1 is a game that I'm very fond of, and on YMF71x cards it only works properly with Adlib sounds. When enabling sound blaster digital sounds, the game has an annoying pause/stutter after playing back each digital sound. I have tried this on MANY chipsets/motherboards and it always behaves the same. The YMF7x4 PCI cards don't have this issue. Well, at least it's better than ESS Solo-1 - with this card the game freezes completely when playing back the first digital sound: https://www.youtube.com/watch?v=P8hkEVd4MLg

carlostex wrote on 2020-12-26, 18:10:

Also can you try an AIL Miles driver game with the Yamaha 7x4 cards and check if it crashes? I suggest to try Dune 2 with Sound Blaster Pro digital sound.

I tested Dune 2 on YMF724 / 440BX chipset multiple times, have had no issues with it.

My AWE64 Gold supports it and has great sound. I guess the importance comes down to number of games that use it which I am not sure about. However I do want to play DN2 one day so I could not live with only a non ADPCM card.

mkarcher wrote on 2020-12-26, 18:23:

The "2.6 bit" makes some sense: You call this mode "8-3 ADPCM" (first time i heard this name, usually I hear 2.6bit or 1:3). It packs 3 samples into 8 bits (I suppose, that's what you intend to express with 8-3). If 3 samples need 8 bits, the average number of bits stored per sample is 8/3 bits, which is approximately 2.6 bits per sample.

Sure but one thing is to talk about approximated ratios, other is to imply that the 3 samples are actually 2.6 bit. Bits can't be fractionary, so either 2 samples share a nibble and stay 2 bits each while the other takes the other nibble or 2 samples are 3 bits each and the remaining is 2 bits only. Something has to give.

carlostex wrote on 2020-12-26, 18:33:

Sure but one thing is to talk about approximated ratios, other is to imply that the 3 samples are actually 2.6 bit. Bits can't be fractionary, so either 2 samples share a nibble and stay 2 bits each while the other takes the other nibble or 2 samples are 3 bits each and the remaining is 2 bits only. Something has to give.

To get the important thing first: I'm not trying to convince you that "2.6 bits" is a good name for this scheme. I'm just trying to point out that the name 2.6-bit ADPCM does in fact have some inner logic that makes sense.

In the case of Create Labs, it is in fact a 3-3-2 scheme, where two samples are encoded using 3 bits each, and the last sample is encoded using 2 bits.

You do not have to split on a by-bit basis. As 6^3 is 216, you can fit 3 numbers ranging between 0 and 5 into a single byte, and even have space for 40 extra symbols. You can even go one higher in one of these numbers, as 7*6*6 = 252, so you can pack a number between 0 and 6, together with two numbers between 0 and 5 into one byte. The information content of a number between 0 and 6 (one of 7 values) expressed in bits is around 2.81 bits and the information content of a number between 0 and 5 (one of 6 possible values) is around 2.58 bits. So fractional bits indeed make sense in certain circumstances.

A common application of a 6*6*6 encoding is the "web safe color palette" that was used by browsers to render true-color pictures. It used 216 of the 256 colors available in 8-bit graphics modes, leaving 40 further colors for standard or theme-dependet colors used by the operating system. This encoding could rightfully be called "2.58 bits per color component".

So, you say that ADPCM is not that relevant?
What are the workarounds that were mentioned above?
Because it seems that the only things creative introduced were ADPCM 2.6 and a few problems, that didn't work so well.
Using ADPCM 2.6 would make people stuck only with creative cards. Was that a way to get people and software producers convinced that creative was the only choice?
Where is the list of games/software that use ADPCM 2.6?

Marmes wrote on 2020-12-26, 21:39:

What are the workarounds that were mentioned above?

See here: Re: Duke Nukem 2 ADPCM fix?

Disclaimer: I haven't used that personally since I have several non-Yamaha sound cards which do support ADPCM.