[alsa-devel] Patchmix-style application for EMU cards

Camilo Polymeris cpolymeris at gmx.net
Fri Apr 18 21:44:46 CEST 2008


> The basic idea is that we have two chips. One is custom FPGA, where all
> the
> physical inputs and outpusts are connected. The second chip is the emu10k
> which is conected to FPGA by a bunch of 32bit  buses. There are 32 buses
> from
> emu10k to FPGA called DSP0 to DSP31 used for playback and 21 buses in
> other
> direction called DSP0 to DSP15 (hexa numbering!) used for capture. 1 bus =
> one audio channel except for higher sample rates (e.g. 96kHz and 192kHz),
> where multiple buses are used to transfer one channel. The FPGA can assign
> any physical input (or playback DSP channel) to any capture DSP channel
> and
> same for outputs (see alsamixer). The multichannel capture on hw:0,2
> captures
> the first 16 channels (DSP0 to DSPD). The multichannel playback on hw:0,3
> is
> routed to DSP0 to DSP15.
> I hope it helps.

That is more or less what I had figured out, but it how are playback_1 to
_16 channels routed to DSP0-15? It seems that it depends on the setting of
Front, Surround, LFE, etc. mixer controls. If they are turned up, I don't
understand what happens, sound to playback channels appears on various DSP
buses, at different levels.
If I turn the Front/Surround/LFE/etc. faders down, I can mix playback
channels to DSP using the "Multichannel PCM Send/Routing/Volume" faders, in
a more or less intuitive way, besides that routing values do not map
directly to DSP buses (i.e. 14-15 map to DSP0-1, but 2-3 map to DSP2-3).
There is also a set of mixer controls called "EMU10k Routing", or similar,
which I haven't even looked at.

> >  or maybe the driver developer can help me out?
> Well, I'm not quite a driver developer, but I think I know E-mu cards well
> to
> answer any questions important for mixer appliacation ;)  So please ask.
> I'd
> like to help you to imporve alsa suport for these excellent cards.
> Best Regards,
> Ctirad
Thanks for your help, and sorry everyone for double-posting


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