USB sound through Deneb question & opinion?

[platon42]

save2600 wrote:
I'd imagine a USB soundcard would have better fidelity than the 8-bit Paula. Can anyone confirm?

Also, what is the load on the CPU like when using the external USB sound? I assume the same since the CPU is
still decoding, but again - with better fidelity?

Sound quality is much better than the original Paula sound, but how much better it is really depends on the quality of the soundcard. Michael Boehmer once hooked a cheap and a not-so-cheap USB soundcard to an memory oscilloscope and the it showed vast differences (steps instead of smooth curves).

CPU load is about the same as with any Zorro soundcard, there's a little conversion overhead, if the samples are not in the right format (as supplied by AHI, e.g. little endian vs. big endian, but I've created 68k-asm optimized versions of each conversion routine for maximum speed). When using Zorro III, it's definately a bit faster than Paula, because with Paula you need to write into chipmem.

[platon42]

sandpiper wrote:
I also managed to get my hands on a used Yamaha Cavit USB Soundboard. This also works with the Deneb. This machine also has a dsp and I was wondering if this dsp could be used  to play mp3s instead of the cpu. An MHI driver perhaps?

The USB Audio spec defines DSP processing features that can be tuned to your needs. However, AHI does not provide control of these kinds of settings, so the audio.class simply ignores them (it should list them in the debug output though).

While USB Audio defines compressed audio output instead of linear PCM (e.g. for MP3), I haven't seen any sound card in the wild that would support it.

Again, a PsdDevlister and PsdErrorlog would be nice to verify if your card would support such a feature.