Re: old mtcoreaudio code doesn't work now
Re: old mtcoreaudio code doesn't work now
- Subject: Re: old mtcoreaudio code doesn't work now
- From: John Draper <email@hidden>
- Date: Sat, 12 Jan 2008 13:50:27 -0800
Michael Thornburgh wrote:
secondly, 8000 samples per second, with one channel, 4 bytes per
sample (Float32), is 32,000 bytes/sec or 256,000 bits/second. how
much data are you actually getting out?
Well, we really want 16 bit samples at 8k/Sec because the GSM Codec
requires it to be in that format... Isn't it just a matter of setting
up the flags correctly?
In my use of your earlier version, we've been able to just use the
MTConversionBuffer structures, and somehow the output from the Mic was
the proper format. However, Robert experienced some problems, then
learned you deprecated the function, and the new function doesn't
appear to give us what we want to satisfy the GSM Codec.
I think all we need to do, is setup the "flags" properly as suggested
by some of the other list members, but we have failed in trying to
locate the proper docs that show us how to setup these flags. We
scanned the Code Audio Header files, but didn't learn much, and since
there is lack of an example, we are purplexed, trying to find these
hidden flags.
finally, although i have no idea what you're using inBuffer for, it's
almost certainly too small to be of much use, being only 1 channel
wide and 94 frames long.
Well - here is where we are so confused... our application is a very
simple Audio Recorder of only Voice Quality. Once we have a buffer of
16 bit signed values thats filled to 1280 bytes (640 samples), we pass
that to a GSM Codec, and out comes 130 bytes of compressed audio we just
put into a buffer.
On the playback side, we uncompress the 130 byte GSM Frame (Actually
two of them - because they have odd number of bytes), back into 16 bit
audio samples for 8k/sec sample rate for playback and pass it to
MTCoreAudio for playback.
Using your old framework running Tiger, we had no problem.
Last year at WWDC, I was tasked to test the application on Leopard and
X-Code 3. We found just one issue that Nick Moss helped us fix,
because the data was not locked down under certain specific conditions,
so we created and subclassed one of your objects and called in
"SmartConditionLock". Way back them, I sent you Email with the
changes for your inspection. I never did get any response back.
Now, when we FINALLY got our Intel Powerbook Pro's we discovered our
application no longer works, and we got the impression it was Apple's
doing. After a while, you responded to Bob's posting.
Bob has been one of my best programmers. Due to a hand and nerve
damage, I'm not much of a programmer these days... Imagine loosing
your abiity to type code... I CAN type, but not for very long... and
after replying to my Email, I'm spent for at least 3 - 4 hours.
because of this problem, I was unable to complete my VIOP application I
worked on back in 2005 and 2006, and got cut from the project only 95%
before completion.
Anyway, I'm sure Robert can use some of your help, and I think He's
working on an idea to do the conversions himself. But we are almost at
the end of our investors patience, and either might wind up ditching
MTCoreAudio alltogether, but we know this is going to severely
complicate our development if we have to work without it. I'm letting
Robert decide on when he's had enough.... So far, he's going to try
just a few more things.
In the meantime, my friend who wants to inherit my G4 is going to have
to wait, because it's the only machine I can use for narrating my book,
then taking dictation using our Audio Voice application we call "Edicta".
The program has been a godsend for me... as my book project has advanced
so far now.
A month go, I met Woz, showed him the application, and he loved it. I
WANTED to send him a signed copy of the program when I get up to
MacWorld next week, but (sigh) I cannot do that now. We also use it to
take minutes for our meetings.
I've known the Woz a long time before he started Apple. We've been very
good friends ever since...
Anyway, I hope the technical description I sent with this mail can give
you a better perspective on what we want to do, and others on the list
familiar with MTCoreAudio can give us some needed tips.
Regards
John
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