I updated the sources. One question. In jcapture, I printf the meter in the console with vertical bars '|' as usual. I calculate an average from 5 callback calls, and I printf the meter inside the callback functions, that is not real safe. Where to printf the meter? Must be inside the infinite loop for(;;)... this way is real safe?
Joan Quintana --- On Fri, 2/24/12, Robin Gareus <[email protected]> wrote: From: Robin Gareus <[email protected]> Subject: Re: [LAD] Tutorial for programming with JACK To: "Joan Quintana" <[email protected]> Cc: [email protected], "Harry Van Haaren" <[email protected]> Date: Friday, February 24, 2012, 5:07 PM Hi Joan, Thanks for sharing those! On 02/24/2012 11:12 AM, Joan Quintana wrote: > Related with this topic, I would like to contribute with 3 pieces of code > made with an educational point of view (though I don't teach audio processing > and I don't consider an expert myself). These examples use libsndfile > library, that is important if the source or the destination of your audio > data is a wav file. > > a) jcapture: > *http://wiki.joanillo.org/images/0/07/Jcapture-1.0.0.tar.gz > reads the data coming from the microphone, and saves a wav file. Shows a > textual signal meter in the console. (I know the existance of jack-capture. I > didn't look at jack-capture code, sure that has better performance and lots > of options, I just wanted the minimal code) The linked tar-ball includes jcapture-0.0.1.cpp that does not save any .wav file. Calling printf() in the jack-callback function is not realtime safe; [but it's perfectly valid for debugging/development purposes and] I guess you simply mixed up the files. FWIW https://github.com/jackaudio/example-clients/blob/master/capture_client.c is very close to the minimal code required to do disk I/O. It does not include a meter, but supports multiple-channel. > b) jplay-sndfile-simple: > *http://wiki.joanillo.org/images/1/1e/Jplay-sndfile-simple-1.0.0.tar.gz > It's just a playback wav file. In the callback function there are two > possibilities: copying blocks of memory; or copying sample by sample, and > this permits a little signal processing (in this simple case just divide the > signal by 2). > I borrowed code from sndfile-jackplay.c (sndfile-tools-1.03, Erik de Castro > Lopo & Jonatan Liljedahl), where is interesting the thread implementation > (playing while reading the file) that I didn't implemented. neat. There's some cruft in it (unused variables, binary (&) vs boolean (&&) AND in line 89) - compile with `-Wall` option: g++ will tell you. Otherwise it'd make a nice addition to https://github.com/harryhaaren/Linux-Audio-Programming-Documentation > c) jplay-sndfile: > *http://wiki.joanillo.org/images/e/e6/Jplay-sndfile-1.0.0.tar.gz > This is more interesting and not simple like the previous. A part of playing > back the file, it permits frequency shifting and frequency sweeping in a > range between .5 and 2. see previous email (reply to Harry). > Hope this helps to somebody, > Joan Quintana > > best, robin
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