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Old 08 March 2014, 16:29   #70
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Join Date: Jul 2012
Location: Aberystwyth, Wales
Posts: 16
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.


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.
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