[gmpi] Re: Topic 7: Audio packaging
- From: RonKuper@xxxxxxxxxxxx
- To: gmpi@xxxxxxxxxxxxx
- Date: Thu, 22 May 2003 09:17:40 -0400
>>>
Everybody seem to agree on this and still I'm not sure.
Having just vectorized a lot of DSP code lately (mostly Altivec but also
MMX/SSE/SSE2) I notived that often my job could have been a
lot easier with interleaved buffers.
<<<
I second that point. Especially when dealing with surround formats, there
is great benefit to having an interleaved representation, since the any SIMD
based code can pull the channel data directly in parallel, without
"swizzling."
Furthermore, the choice of whether to intelreave or not should consider
locality of reference. Do separate mono streams keep the CPU cache warmer
than interleaved? (I did some dumb benchmarking with stereo and saw no
discernable difference. This may differ with higher channel counts.)
Another potential complication with non-interleaved is how to handle plugins
that take, say, a two 5.1 input stream, plus one mono side-chain stream.
How can you effectively make heads or tails of this, even with a "hints"
structure. Some channels naturally come in groups and may need to processed
that way.
Finally, let's not forget the kinds of driver models out there. ASIO is
more amenable to mono streams, since that's the driver API. But wave,
DirectSound and WDM seem to favor interleave. I'm not a driver guy, but it
would interesting to know which of interleaved vs. not is the more natural
representation for hardware.
I'm thinking we should should allow interleaved streams, but have the
standard GMPI library include standard packing and unpacking components.
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