Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
 
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: audio capture

Alex Nicolaou <email@hidden> wrote:

>Thanks, I independantly came across this example while looking for the
>QT examples in /Developer. I then spent 40 minutes figuring out what
>your mail told me - that no sampling frequencies other than 44.1 khz are
>available :-)

The available parameters can be queried by walking through the
AudioSystem's Mixers and their sub-elements. This would have been one of
the more useful things the demo could have done, but maybe it was too
practical.

The JSInfo program is one way of exploring what's available. Its GUI is
pretty horrific (a finalist in the Worst Use of Tables category), though it
isn't completely unusable:
<http://www.jsresources.org/apps/jsinfo.html>

The recording input is the one whose class is ...SimpleInputDevice. It has
a DataLine class that's a TargetDataLine. Click that line and you'll see
the supported AudioFormats, which are all 44 KHz.


>However, on my system, 8-bit recording is supported (10.3 and Java 1.4.2
>with a plantronics headset).

As I check this right now in JSInfo, I see that my configuration supports
8-bit input, too. I didn't notice that before.


>As JMF claims it uses JavaSound to support recording, I might give it
>another try - though if you know off the top of your head a nice java
>api way to convert 44.1khz samples to 8khz samples I'd appreciate it.

Search for "downsampling" at Tritonus. Or visit a search engine.

I recall reading something quite a while back about a Java implementation
that was pretty good, but I can't remember anything about it. The hard
part is doing good enough filtering on the original sampled signal to avoid
aliasing artifacts in the downsampled signal. That takes a really sharp
filter, which takes a lot of coefficients, which takes a lot of cycles.

-- GG
_______________________________________________
java-dev mailing list | email@hidden
Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/java-dev
Do not post admin requests to the list. They will be ignored.

References: 
 >Re: audio capture (From: Greg Guerin <email@hidden>)



Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2007 Apple Inc. All rights reserved.