Porting/Audio/Q and A RE-PA

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(A list of questions Jonwil asked Juho Hämäläinen in IRC query. Posted here for public discussion and documenting the answers)
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Revision as of 12:26, 24 October 2014

jonwil	Page 15 of this PDF http://linuxplumbersconf.org/2009/slides/Jyri-Sarha-audio_miniconf_slides.pdf shows a block diagram of the N900 audio system (or at least what I assume is the N900 audio system). Is there any chance you can expand on which algorithms (e.g. stw, xprot, eap, aep, drc, eq, iir, fir etc) match with the blocks marked "Mic EQ", "music processing", "recording processing",...
	jonwil	..."transducer processing" and "call audio processing"?
	jonwil	I have been examining the Meego code and the Harmattan code (both the open bits in pulseaudio-modules-meego and the closed bits in pulseaudio-nokia) with a view to possibly using the blobs or parts of them for the Neo900 audio work (since they are more open than the ones on the N900). Comparing what Meego has to what Fremantle has, it would appear as though the Meego and Harmattan blobs are...
	jonwil	...missing functions labeled stw. Are you aware of any other pieces in the Meego or Harmattan blobs that are missing or that might have been built differently? (ignoring anything to do with different versions of compilers, PulseAudio, libc or other things, just talking about the actual algorithms and such in the pulseaudio-nokia blobs). Or for that matter anything that is present in the...
	jonwil	...Meego or Harmattan blobs but isn't used on Fremantle?
	jonwil	Other than the cmtspeech stuff, are you aware of anything in the nokia Fremantle Pulseaudio blobs that talks to or is dependent on the N900 cellular modem?
	jonwil	Which of these Nokia algorithms are necessary for safe system functioning and which are just going to give not-so-nice audio if we dont have them? Obviously xprot is something we probably need in order to protect the speakers/earpiece/etc from damage but what else? (the cellular modem we are using in the Neo900 already does all sorts of voice processing so identifying which bits we need and...
	jonwil	...which bits we can leave to the cellular modem will save us a lot of time)
	jonwil	Are you aware of open-source implementations of algorithms similar to the proprietary Nokia ones?
	jonwil	Anything you can share on these questions (whenever you have the time) will be great (if you cant share some of this because you dont have the info, have forgotten it or are unwilling/unable to share due to NDA, that's ok, anything you CAN share on this pulseaudio-nokia stuff will really help us out)
	jonwil	Some more questions for when you have the time:
	jonwil	Do you know if the stereo widening stuff is actually used on the N900 on Fremantle? All of the .parameters files that control the blobs set x-maemo.stereo-widening = "false" which I assume means "turn it off". If its in fact not used that means we can ignore it (it would also explain why its not even compiled in for Meego)
	jonwil	nb_eeq is "narrowband ear equalizer"
	jonwil	nb_meq is "narrowband mic equalizer"
	jonwil	wb_eeq is "wideband ear equalizer"
	jonwil	wb_meq is "wideband mic equalizer"
	jonwil	What is the difference between "narrowband" and "wideband" here?
	jonwil	What is xprot displacement?
	jonwil	Can you tell me which of these sets of parameters will be tied to the specific details of the microphone in the N900 or of the FMTX in the N900? (bluetooth is digital so changing bluetooth chips shouldn't change the way the audio needs to be processed and we are using the same earpiece, speakers, headphone, lineout and tvout setup so those wont change)
	jonwil	aep
	jonwil	nb_eeq
	jonwil	nb_meq
	jonwil	wb_eeq
	jonwil	wb_meq
	jonwil	mumdrc.ul
	jonwil	mumdrc.dl
	jonwil	limiter.ul
	jonwil	limiter.dl
	jonwil	xprot
	jonwil	That will tell us which bits we need to dig deep into and retune for our needs
	jonwil	retune/replace
	jonwil	BIG thankyou for any help you may give btw, its so great to find someone who actually understands this alphabet soup of audio processing