[Speex-dev] Buffer size/rate woes

B. Mitchell Loebel multinode at earthlink.net
Tue May 8 03:24:50 PDT 2007

Hello Zack:

Excuse me if I'm jumping into something completely wrongly, but ...

I'm doing something similar right now on the Mac working with G.729. 
I'm working on the decode end of the problem and interfacing with 
what the Mac developer community calls an Audio Unit (AU) to get to 
their D/A and speakers. So my code decodes the compressed file and 
streams the PCM into an AU that I configured with the frame size and 
rate I want and samples widths that I specify (in my case 16 bits). 
I'm using their default AU in output mode. I believe you would 
configure an AU in an input mode which would allow you to interface 
with some hardware sound input and give you the frame rate, number of 
samples, and sample widths that SPEEX wants.

I suggest that you check into 
<http://coreaudio-api@lists.apple.com/>coreaudio-api at lists.apple.<http://coreaudio-api@lists.apple.com/>com. 
I have an active issue going back and forth right now with my 
scenario. Lots of very good help up there. You may have to subscribe 
to read or write the lists. Let me know if you have a problem with that.

Take care ... hope this helps.

At 01:46 AM 5/8/2007 -0600, zmorris at mac.com wrote:
>Hi All, I am trying to get speex working on the Mac and am running
>into issues.  I got the examples working, but am now trying to make
>speex, which expects 8000 Hz and 160 samples per buffer (320 bytes
>per buffer), work with the Mac's built-in audio recording, which uses
>either 11025, 22050, or 44100 Hz and 1024 samples per buffer (2048
>bytes per buffer).
>I just need to know if there is a way to make speex run at say 11025
>Hz with maybe 512 (or other power of 2) samples per buffer.
>Otherwise there is going to be a lot of code handling remainders for
>each buffer and downsampling.
>Also, does speex use a timer of any kind?  Or does it just process
>blocks as they are given?  I just mean for general encoding, not
>echoes, etc.
>Speex-dev mailing list
>Speex-dev at xiph.org

B. Mitchell Loebel, Executive 
Director                              408 425-9920

The Tech Startup Connection
(formerly The PARALLEL Processing Connection) 
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