6 Apr
2006
6 Apr
'06
10:32 a.m.
Lee Revell wrote:
Lately however Creative/EMU's DSP cards have been
getting great reviews
(X-Fi, EMU 1212M, etc) - they seem to have fixed a lot of the common
complaints about the SBLive! based devices (crappy codecs, horrible
resampling). And they are still damn cheap ($200-300 tops IIRC) but
have no Linux drivers. This might be an area to investigate, but I
suspect you would need years of development to produce a device of that
quality for anywhere near Creative's price point.
Creative have actually donated an X-Fi and an EMU1212M to me.
No datasheets, but at least having the hardware is a start. (Creative
pass me some datasheets for other cards though)
I have currently got as far as horrible noises coming from the EMU1212M.
So, after some more reverse engineering, we should have that working.
The X-Fi is a totally new beast, so that is a long way off currently.
My point is that with reverse engineering, we can get these commercial
cards working with Linux, so do we really need to build our own open
source ones?
Sound cards are not nearly as complicated as graphics cards, so the
reverse engineering task is less and therefore do-able.
Saying that, the X-Fi might be an exception.
If I was designing a GPL sound hardware, I would want to separate the
DAC and ADC tasks from any other processing done by the card.
I.e. The card would do all the DSP, FPGA processing and only have
digital external links. Then have the DAC and ADC as a separate external
device.
The main task would be designing a good interface to the DAC and ADCs
that would not require any firmware on the DAC and ADC device.
The EMU1212M has this separation. It has two parts:
a) The EMU1010 is the DSP/FPGA card.
b) The EMU0202 is the DAC/ADC device.
There is another area of GPL development work that might be of interest
to the list and that is the Software Defined Radio open source work
going on at the moment. A lot of that is based around using a sound card
for the ADC, but sampling at 96khz/24bit.
One has an external device that does the down mixing of RF to an IF of
about 32khz. The sound card then samples that IF at 96khz and then
processes the IF.
The main requirement for SDR is dynamic range, so the 24bit is
important. So the aim of getting a very good ADC for 96khz/24bit in the
SDR market, is the same as that in the Audio market. So, you might be
able to combine efforts.
James