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| author | Guenter Geiger <ggeiger@users.sourceforge.net> | 2003-05-09 16:04:00 +0000 |
|---|---|---|
| committer | Guenter Geiger <ggeiger@users.sourceforge.net> | 2003-05-09 16:04:00 +0000 |
| commit | 9c0e19a3be2288db79e2502e5fa450c3e20a668d (patch) | |
| tree | ca97ce615e037a533304fc4660dcf372ca3b9cd6 /pd/portaudio/docs/pa_impl_guide.html | |
| parent | ef50dd62804d54af7da18d8bd8413c0dccd729b8 (diff) | |
This commit was generated by cvs2svn to compensate for changes in r610,
which included commits to RCS files with non-trunk default branches.
svn path=/trunk/; revision=611
Diffstat (limited to 'pd/portaudio/docs/pa_impl_guide.html')
| -rw-r--r-- | pd/portaudio/docs/pa_impl_guide.html | 197 |
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diff --git a/pd/portaudio/docs/pa_impl_guide.html b/pd/portaudio/docs/pa_impl_guide.html new file mode 100644 index 00000000..50abc304 --- /dev/null +++ b/pd/portaudio/docs/pa_impl_guide.html @@ -0,0 +1,197 @@ +<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> +<html> +<head> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <meta name="GENERATOR" content="Mozilla/4.79 [en] (Windows NT 5.0; U) [Netscape]"> + <meta name="Author" content="Phil Burk"> + <meta name="Description" content="Internal docs. How a stream is started or stopped."> + <meta name="KeyWords" content="audio, tutorial, library, portable, open-source, DirectSound,sound, music, JSyn, synthesis,"> + <title>PortAudio Implementation - Start/Stop</title> +</head> +<body> + +<center><table COLS=1 WIDTH="100%" BGCOLOR="#FADA7A" > +<tr> +<td> +<center> +<h1> +<a href="http://www.portaudio.com">PortAudio</a> Implementation Guide</h1></center> +</td> +</tr> +</table></center> + +<p>This document describes how to implement the PortAudio API on a new +computer platform. Implementing PortAudio on a new platform, makes it possible +to port many existing audio applications to that platform. +<p>By Phil Burk +<br>Copyright 2000 Phil Burk and Ross Bencina +<p>Note that the license says: <b>"Any person wishing to distribute modifications +to the Software is requested to send the modifications to the original +developer so that they can be incorporated into the canonical version."</b>. +So when you have finished a new implementation, please send it back to +us at "<a href="http://www.portaudio.com">http://www.portaudio.com</a>" +so that we can make it available for other users. Thank you! +<h2> +Download the Latest PortAudio Implementation</h2> +Always start with the latest implementation available at "<a href="http://www.portaudio.com">http://www.portaudio.com</a>". +Look for the nightly snapshot under the CVS section. +<h2> +Select an Existing Implementation as a Basis</h2> +The fastest way to get started is to take an existing implementation and +translate it for your new platform. Choose an implementation whose architecture +is as close as possible to your target. +<ul> +<li> +DirectSound Implementation - pa_win_ds - Uses a timer callback for the +background "thread". Polls a circular buffer and writes blocks of data +to keep it full.</li> + +<li> +Windows MME - pa_win_wmme - Spawns an actual Win32 thread. Writes blocks +of data to the HW device and waits for events that signal buffer completion.</li> + +<li> +Linux OSS - pa_linux - Spawns a real thread that writes to the "/dev/dsp" +stream using blocking I/O calls.</li> +</ul> +When you write a new implementation, you will be using some code that is +in common with all implementations. This code is in the folder "pa_common". +It provides various functions such as parameter checking, error code to +text conversion, sample format conversion, clipping and dithering, etc. +<p>The code that you write will go into a separate folder called "pa_{os}_{api}". +For example, code specific to the DirectSound interface for Windows goes +in "pa_win_ds". +<h2> +Read Docs and Code</h2> +Famialiarize yourself with the system by reading the documentation provided. +here is a suggested order: +<ol> +<li> +User Programming <a href="pa_tutorial.html">Tutorial</a></li> + +<li> +Header file "pa_common/portaudio.h" which defines API.</li> + +<li> +Header file "pa_common/pa_host.h" for host dependant code. This definces +the routine you will need to provide.</li> + +<li> +Shared code in "pa_common/pa_lib.c".</li> + +<li> +Docs on Implementation of <a href="pa_impl_startstop.html">Start/Stop</a> +code.</li> +</ol> + +<h2> +Implement Output to Default Device</h2> +Now we are ready to crank some code. For instant gratification, let's try +to play a sine wave. +<ol> +<li> +Link the test program "pa_tests/patest_sine.c" with the file "pa_lib.c" +and the implementation specific file you are creating.</li> + +<li> +For now, just stub out the device query code and the audio input code.</li> + +<li> +Modify PaHost_OpenStream() to open your default target device and get everything +setup.</li> + +<li> +Modify PaHost_StartOutput() to start playing audio.</li> + +<li> +Modify PaHost_StopOutput() to stop audio.</li> + +<li> +Modify PaHost_CloseStream() to clean up. Free all memory that you allocated +in PaHost_OpenStream().</li> + +<li> +Keep cranking until you can play a sine wave using "patest_sine.c".</li> + +<li> +Once that works, try "patest_pink.c", "patest_clip.c", "patest_sine8.c".</li> + +<li> +To test your Open and Close code, try "patest_many.c".</li> + +<li> +Now test to make sure that the three modes of stopping are properly supported +by running "patest_stop.c".</li> + +<li> +Test your implementation of time stamping with "patest_sync.c".</li> +</ol> + +<h2> +Implement Device Queries</h2> +Now that output is working, lets implement the code for querying what devices +are available to the user. Run "pa_tests/pa_devs.c". It should print all +of the devices available and their characteristics. +<h2> +Implement Input</h2> +Implement audio input and test it with: +<ol> +<li> +patest_record.c - record in half duplex, play back as recorded.</li> + +<li> +patest_wire.c - full duplex, copies input to output. Note that some HW +may not support full duplex.</li> + +<li> +patest_fuzz.c - plug in your guitar and get a feel for why latency is an +important issue in computer music.</li> + +<li> +paqa_devs.c - try to open every device and use it with every possible format</li> +</ol> + +<h2> +Debugging Tools</h2> +You generally cannot use printf() calls to debug real-time processes because +they disturb the timing. Also calling printf() from your background thread +or interrupt could crash the machine. So PA includes a tool for capturing +events and storing the information while it is running. It then prints +the events when Pa_Terminate() is called. +<ol> +<li> +To enable trace mode, change TRACE_REALTIME_EVENTS in "pa_common/pa_trace.h" +from a (0) to a (1).</li> + +<li> +Link with "pa_common/pa_trace.c".</li> + +<li> +Add trace messages to your code by calling:</li> + +<br><tt> void AddTraceMessage( char *msg, int data );</tt> +<br><tt>for example</tt> +<br><tt> AddTraceMessage("Pa_TimeSlice: past_NumCallbacks ", +past->past_NumCallbacks );</tt> +<li> +Run your program. You will get a dump of events at the end.</li> + +<li> +You can leave the trace messages in your code. They will turn to NOOPs +when you change TRACE_REALTIME_EVENTS back to (0).</li> +</ol> + +<h2> +Delivery</h2> +Please send your new code along with notes on the implementation back to +us at "<a href="http://www.portaudio.com">http://www.portaudio.com</a>". +We will review the implementation and post it with your name. If you had +to make any modifications to the code in "pa_common" or "pa_tests" <b>please</b> +send us those modifications and your notes. We will try to merge your changes +so that the "pa_common" code works with <b>all</b> implementations. +<p>If you have suggestions for how to make future implementations easier, +please let us know. +<br>THANKS! +<br> +</body> +</html> |