Am 04.02.2011 02:11, schrieb Niels Mayer: > On Wed, Feb 2, 2011 at 12:48 PM, Stefan Kost <enso...@hora-obscura.de > <mailto:enso...@hora-obscura.de>> wrote: > > Sorry for the very late reply. One thing to mention is that the CPU load > for > pulse is going wown quite a bit when plugin headphones. Otherwise it runs > some > extra processing needed to accomodate the speakers. > > > Since there is a lot of extra audio processing going on, would employing a > library like "nova-simd", announced below, help out with the situation -- e.g. > writing the handset speaker-equalization and some of the audio mixing > functionality using more efficient instructions? What looks interesting is the > claimed support for both ARM Neon, Altivec, and Atom: See > http://tim.klingt.org/code/projects/nova-simd/repository and forwarded > announcement below.
Interesting. Need to take a closer look. Please note that pulseaudio is written in C. Orc might be better suitable for PA also. Stefan > > .... > > Regarding pulseaudio, > in > http://code.google.com/p/ytd-meego/wiki/CitizenJournalismWithYoutubeDirectForMeego#Pulseaudio:_Connecting_Audio_Subsystem,_Microphone_and_Speakers > -- Note > all the "ins and outs" back and forth between kernel and user space. > > Architecturally, the system seems inverted, especially since you have to go > back > out to ALSA for bluetooth. Why not keep it all in kernel space?? > > Or better yet: employ analog mixing and multiple DAC's -- only one or two > needing to be "hi-fi" and the others for notifications and telephony can be > quite cheap low-rate, low-accuracy DAC's and ADC's. Yes analog mixing and > routing is hard to do in a mixed signal environment; but is the power > consumption of a few DACs and op-amps even close to that of needing a > fraction > of the CPU running constantly just to do what a few resistors and an op-amp > can > do? To say nothing about the potential sound quality improvement of not > needing > to resample any of the mixed outputs, nor worry about synchronizing or locking > rates between different subsystems, and all the other benefits of analog > summing: http://emusician.com/mag/emusic_sum_tracks/ ... (hopefully the > flamewars that will ensue about this controversial topic will cancel out the > flamewars on pulseaudio :-) ) . > > What I'm proposing for the low-power/handset world isn't that far off from the > audio system needed back when CPU's had computational power that made digital > mixing for notifications, telephony, or music playback unthinkable: the analog > mixing built into the http://en.wikipedia.org/wiki/AC'97 > <http://en.wikipedia.org/wiki/AC'97> spec (and associated hardware), but > updated > for the handset world. I'm sure that's not going to happen anytime soon, but I > can dream? > > ........... > > Anyways, here's the announcement: > > http://music.columbia.edu/pipermail/andraudio/2011-February/000098.html > ...................... > [andraudio] nova-simd suite updated for arm neon > Dan Stowell > Thu Feb 3 04:48:36 EST 2011 > > Hi - > > "nova-simd" is a C++ header-only template library for taking advantage > of SIMD instructions in the kind of DSP processes used in audio > processing (i.e. not just basic stuff like vectorised mul+add and loop > unrolling, but also some more audio-specific things like ramps, > distortions). > > It's created by Tim Blechmann and it lives here: > http://tim.klingt.org/code/projects/nova-simd/repository > > It was originally implemented for SSE and SSE2 - we use it in > SuperCollider and it gives us massive performance improvements on > intel chips. We've just added NEON (and Altivec) implementations too, > so we should be able to boost performance on android and ios. > > The ARM NEON support is new and doesn't yet implement all the > speedups, but should be useful for anyone wanting to implement C++ DSP > for Android devices with SIMD speedups - especially if you're thinking > about cross-platform code since the API is implemented for other chips > too. > > Dan > ................. > > Niels > http://nielsmayer.com _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev