Hi Michel,
>- it would be extremely useful if harware-synthesized audio (digital domain
of
>course) could be got back in real time from the card for further use by
>software (an obvious use being recording it to a file), as well as going to
>the card's audio out connectors.
At least for some implementations of the whole MPEG-4 standard, this
will have to be the case. In a full MPEG-4 implementation that includes
AudioBIFS post-production as well as SAOL support, the synthesis is
not the last step in the processing chain. The result of the synthesis
is further manipulated (ie by mixing or delay) by the AudioBIFS
instructions. Thus, for hardware/software implementations, it is
necessary that the SA synthesizer, if implemented in hardware,
return the samples back to the AudioBIFS processor.
(Some implementations may integrate the AudioBIFS part and the SA part
of MPEG-4 more deeply than is required; there's some good reasons for
doing so. In such a case, the two parts could move in conjunction
to the hardware side and there wouldn't necessarily be a reason to
return the samples to the host).
>- even better, allow the use of the card as an SAOL processing farm : an
API
>could be provided so that software can request processing of successive
sample
>frame blocks from the card and get them back as fast as the card can
compute
>them. Ideally you would implement a vst2 "proxy" dll for that.
>
>Is point 2 technically feasible ? Anything going on along these lines ?
>(Forgive me if the questions have been raised before).
It seems to me that latency issues are problematic if you want to
do real-time processing in such a scenario. It requires two DMAs for
each roundtrip cycle to and from the host, and so if you are trying
to do several stages of processing, the DMA latency will add up
quickly.
But I'm not an expert in such matters; there are people here who
understand these things much better than I.
Best,
-- Eric
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