Prisma Megamix. New soundcard for classics!

[Retrofan]

Originally Posted by NovaCoder

AmigaKit were kind enough to set my a prototype card so that I could try and update some of my ports to use it for playing back compressed music (eg ScummVM).

Ok got it working -> [ Show youtube player ]

Just a question Nova: do you think using the Prisma would free some CPU use and then it would be possible for example to run Full Throttle on a 030?

[alexh]

Unlikely. This isn't a traditional sound card. It doesn't have hardware MIDI.

Had they used the earlier VS1053b version it would have had some flavour of MIDI.

But let's see what Nova thinks of it...

[amigakit.com]

The VS1053b lacks a few other interesting features on the encoding side, we wanted to explore audio file format conversion possibilities also with this card.

Could some games that use MIDI have their sounds preconverted into other audio formats, compatible with Prisma?

[alexh]

It is my belief that the main CPU power is used for the multi-channel sample rate conversion and stereo down-mix.

At first glance the VS1063 doesn't have capabilities to accelerate these functions.

All I can gleam from the datasheet (with respect to sound output) is :

1) Digital compressed stereo in -> Decompressed -> Analog Stereo Out.
2) Digital uncompressed stereo in -> Analog stereo out.

It has a very limited digital pcm mixer which can overlay sideband mono 16-bit digital uncompressed PCM over whatever you're processing mainband. Possibly usable for SFX over music.

[Retrofan]

This is what they published: http://www.a-eon.com/18-10-2013-2.pdf

[NovaCoder]

Originally Posted by Retrofan

Just a question Nova: do you think using the Prisma would free some CPU use and then it would be possible for example to run Full Throttle on a 030?

The basic plan at this stage is to off-load music decompression to this card (instead of using the CPU to do the decompression work) and then use AHI/Paula to play SFX/speech as per normal. Full Throttle and some other games support FLAC/OGG for music playback, other games need MIDI support for music.

These are very early days so I have no idea what the quality will be like (esp when using the clock-port). I also don't know how many CPU cycles this approach will free up yet.

It's a shame it's not a 'real' sound card with stereo 16bit 44Khz AHI support, that would be really cool. I guess the clock-port would struggle to pump that much data anyway? It doesn't sound like the AHI driver is much of a priority and it probably wouldn't offer any advantage over just using Paula (as far as I can tell).

Some kind of MIDI support would also be a nice addition if there was ever going to be a V2 card.

[voyager]

The midi capability of the VS1053b are very bad, they sound like the old OPL3.
Just sent midi data true the serial port. You can buy a roland sound canvas cheap.

[alexh]

Originally Posted by NovaCoder

It's a shame it's not [got] stereo 16bit 44Khz AHI support

It is be capable of stereo 16-bit 44KHz PCM playback.

Originally Posted by NovaCoder

It doesn't sound like the AHI driver is much of a priority

Bummer.

Originally Posted by NovaCoder

it probably wouldn't offer any advantage over just using Paula (as far as I can tell).

Higher precision audio at higher sample rates.

I dunno what CPU/bandwidth overhead of the 14-bit Paula munge is?

[voyager]

You really need 44 KHz, if you re sample to 48 KHz it will eat 80% cpu time on a 030@56
But on the other hand AHI on a clockport device.. playing a mod true the clockport on the delfina eats away all the cpu time I have, its not really useful :-(

[Spirantho]

One thing I want to clarify:

This Prisma Megamix is not a sound card like a Prelude or a Delfina. I can't stress that enough. It's kind of like the MAS player except more useful, because it does practically every format, and doesn't have to sit externally, and yet also mixes Paula and has an S/PDIF port. It's a music card, not a "sound" card, if you see what I mean.

This is why the AHI driver is a lower priority than the music functionality. The AHI driver is just a way of getting CD-quality audio out of basic Amiga - it will always be limited because it's using a decoder chip, not a full sound chip. There will always be limitations such as the latency and the overhead of pushing raw data to the Prisma, especially on such a slow bus as the clockport. It will only ever support two channels - one Left, one Right - there should be software mixing but of course this introduces CPU load and more latency.

The Paula input is mixed in in hardware - the VS chip supports hardware mixing in stereo at up to 192KHz (kind of pointless with a Paula ). This is covered in section 11.11.4 for anyone who has the datasheet The mixed output is then piped over the analogue output and also digitally to the S/PDIF module.

@alexh

The PCM mixer is something I've not looked at yet. It could in theory give an extra AHI channel, but I suspect the CPU load, particularly on the clockport, would just be too great, and it would disable the AD Mixer.

[Spirantho]

Originally Posted by alexh

Why is it pointless with a Paula?

It is called the "AD" mixer because one source has to be an analog source and the other the incoming digital data. So presumably one source is Paula and the other is Digital data?

That's all we need in this case, though. We need to get Paula audio in in stereo, and mix it with the decompressed audio.
This is what I mean when I say the AHI driver will be very limited - it will only be two channels (or alternatively, more with software mixing).
The Prisma is a music card - when you're doing stereo music, you only need two channels usually - I would never expect a codec decoder chip like this to support hardware mixing of digital streams. That's the domain of sound cards.

[Retrofan]

Originally Posted by Spirantho

... It's kind of like the MAS player except more useful, because it does practically every format.

The MAS player releases as much CPU cycles that you can play an MP3 with any stock Amiga. If the Prisma could make the same it would be possible to play Full Throttle on a 030 (Well, just my opinion).

http://eab.abime.net/showpost.php?p=801887&postcount=8

If it could make something similar with more formats...

[Spirantho]

The Prisma can run a high bitrate mp3 on a 7MHz A2000.... the only difficulty is that it needs to keep the chip fed in a CIA interrupt so as long as the Amiga is able to service a hardware interrupt, it should be ok. Thr IRQ routine is written in 68k assembler to make it as fast as I can get it!

[NovaCoder]

Manage to get it playing a compressed music file last night

[ Show youtube player ]

[daxb]

@Spirantho:
When you say "AHI driver will be very limited - it will only be two channels (or alternatively, more with software mixing)." Do you mean only the two channels limit, or something else? And can you tell what need more then 2 channels except some few games.

What I find more important is full-duplex feature (playing, recording at the same time). Don`t know if the card supports it or not.

[Spirantho]

It's only really games that need more than 2 channels. My main aim with the AHI driver is just to be able to play weirder audio streams like SID tunes or emulator outputs, that sort of thing... where there's only one stream but it's not just standard compressed audio.
I'm afraid it's only half duplex, though. You could buy two Prismas for doing both at the same time if you have enough Zorro slots, but the VS chip can only do data in or data out, sorry!

[Retrofan]

Originally Posted by NovaCoder

Manage to get it playing a compressed music file last night

[ Show youtube player ]

I suposse that's just a test for other games appart of ScummVm, as reading I found this:

http://scummvm.org/faq/#4_3

"4.3. Does ScummVM support using MP3/Ogg/FLAC files instead of the original MIDI music?
No. If all the game does is to play or loop a tune it would be possible, but many of the games do fancy stuff like smooth transitions from one tune to another, or turn individual instruments on and off, etc. There's simply no way ScummVM could take a piece of digital music and emulate that kind of behavior.

This question usually comes up in connection with Sam & Max Hit the Road (which has a few unused bonus audio tracks on the CD) and Monkey Island 2 (which is sometimes distributed on the same CD as the version of Monkey Island 1 that uses CD audio). Both of these games do far too much fancy stuff to even consider an idea like this."

Originally Posted by voyager

The midi capability of the VS1053b are very bad, they sound like the old OPL3.
Just sent midi data true the serial port. You can buy a roland sound canvas cheap.

I've got a Roland, and I would like ScummVm could have Midi support, but it wasn't implemented in Nova's version although it is shown on the options.

I've tried with the other Scumm version, but the sound wasn't working here even.

[Don_Adan]

Originally Posted by Spirantho

It's only really games that need more than 2 channels. My main aim with the AHI driver is just to be able to play weirder audio streams like SID tunes or emulator outputs, that sort of thing... where there's only one stream but it's not just standard compressed audio.
I'm afraid it's only half duplex, though. You could buy two Prismas for doing both at the same time if you have enough Zorro slots, but the VS chip can only do data in or data out, sorry!

Don't better is add more VS1063 chips for one Prisma card for make multichannel soundcard? Even two VS1063 chips is better option than single VS1063 chip, of course the best can be eight VS1063 chips for one Prisma card.

[Spirantho]

No, that's not what the Prisma is about. The Prisma is a music card - the VS1063 is not a retargetable audio card. There's a lot more to it than just number of channels.

Even with 8 VS1063s on there, you'd still be much better off with a Prelude or something for normal audio.

[Don_Adan]

Originally Posted by Spirantho

No, that's not what the Prisma is about. The Prisma is a music card - the VS1063 is not a retargetable audio card. There's a lot more to it than just number of channels.

Even with 8 VS1063s on there, you'd still be much better off with a Prelude or something for normal audio.

Maybe Prelude is much better, but more VS1063s chips or other (optional) MIDI soundchip, can be useful too.