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Diffstat (limited to 'portaudio/doc/src/tutorial/blocking_read_write.dox')
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diff --git a/portaudio/doc/src/tutorial/blocking_read_write.dox b/portaudio/doc/src/tutorial/blocking_read_write.dox new file mode 100644 index 0000000..8905ee3 --- /dev/null +++ b/portaudio/doc/src/tutorial/blocking_read_write.dox @@ -0,0 +1,68 @@ +/** @page blocking_read_write Blocking Read/Write Functions +@ingroup tutorial + +PortAudio V19 adds a huge advance over previous versions with a feature called Blocking I/O. Although it may have lower performance that the callback method described earlier in this tutorial, blocking I/O is easier to understand and is, in some cases, more compatible with third party systems than the callback method. Most people starting audio programming also find Blocking I/O easier to learn. + +Blocking I/O works in much the same way as the callback method except that instead of providing a function to provide (or consume) audio data, you must feed data to (or consume data from) PortAudio at regular intervals, usually inside a loop. The example below, excepted from patest_read_write_wire.c, shows how to open the default device, and pass data from its input to its output for a set period of time. Note that we use the default high latency values to help avoid underruns since we are usually reading and writing audio data from a relatively low priority thread, and there is usually extra buffering required to make blocking I/O work. + +Note that not all API's implement Blocking I/O at this point, so for maximum portability or performance, you'll still want to use callbacks. + +@code + /* -- initialize PortAudio -- */ + err = Pa_Initialize(); + if( err != paNoError ) goto error; + + /* -- setup input and output -- */ + inputParameters.device = Pa_GetDefaultInputDevice(); /* default input device */ + inputParameters.channelCount = NUM_CHANNELS; + inputParameters.sampleFormat = PA_SAMPLE_TYPE; + inputParameters.suggestedLatency = Pa_GetDeviceInfo( inputParameters.device )->defaultHighInputLatency ; + inputParameters.hostApiSpecificStreamInfo = NULL; + + outputParameters.device = Pa_GetDefaultOutputDevice(); /* default output device */ + outputParameters.channelCount = NUM_CHANNELS; + outputParameters.sampleFormat = PA_SAMPLE_TYPE; + outputParameters.suggestedLatency = Pa_GetDeviceInfo( outputParameters.device )->defaultHighOutputLatency; + outputParameters.hostApiSpecificStreamInfo = NULL; + + /* -- setup stream -- */ + err = Pa_OpenStream( + &stream, + &inputParameters, + &outputParameters, + SAMPLE_RATE, + FRAMES_PER_BUFFER, + paClipOff, /* we won't output out of range samples so don't bother clipping them */ + NULL, /* no callback, use blocking API */ + NULL ); /* no callback, so no callback userData */ + if( err != paNoError ) goto error; + + /* -- start stream -- */ + err = Pa_StartStream( stream ); + if( err != paNoError ) goto error; + printf("Wire on. Will run one minute.\n"); fflush(stdout); + + /* -- Here's the loop where we pass data from input to output -- */ + for( i=0; i<(60*SAMPLE_RATE)/FRAMES_PER_BUFFER; ++i ) + { + err = Pa_WriteStream( stream, sampleBlock, FRAMES_PER_BUFFER ); + if( err ) goto xrun; + err = Pa_ReadStream( stream, sampleBlock, FRAMES_PER_BUFFER ); + if( err ) goto xrun; + } + /* -- Now we stop the stream -- */ + err = Pa_StopStream( stream ); + if( err != paNoError ) goto error; + + /* -- don't forget to cleanup! -- */ + err = Pa_CloseStream( stream ); + if( err != paNoError ) goto error; + + Pa_Terminate(); + return 0; +@endcode + + +Previous: \ref querying_devices | Next: \ref exploring + +*/
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