diff options
Diffstat (limited to 'src/polyp/stream.h')
| -rw-r--r-- | src/polyp/stream.h | 75 |
1 files changed, 62 insertions, 13 deletions
diff --git a/src/polyp/stream.h b/src/polyp/stream.h index bb5aa764..6367e868 100644 --- a/src/polyp/stream.h +++ b/src/polyp/stream.h @@ -69,7 +69,7 @@ * * \subsection bufattr_subsec Buffer attributes * - * Playback and record streams always have a buffer as part of the data flow. + * Playback and record streams always have a server side buffer as part of the data flow. * The size of this buffer strikes a compromise between low latency and * sensitivity for buffer overflows/underruns. * @@ -133,33 +133,82 @@ * monitoring the current latency. * * To get the raw data needed to calculate latencies, call - * pa_stream_get_timing_info(). This will give you a pa_timing_info structure - * that contains everything that is known about buffers, transport delays - * and the backend active in the server. + * pa_stream_get_timing_info(). This will give you a pa_timing_info + * structure that contains everything that is known about buffers, + * transport delays and the backend active in the server. * - * If a more simplistic interface is prefered, you can call - * pa_stream_get_time() or pa_stream_get_latency(). These will do all the - * necessary calculations for you. + * This structure is updated every time a + * pa_stream_update_timing_info() operation is executed. (i.e. before + * the first call to this function the timing information structure is + * not available!) Since it is a lot of work to keep this structure + * up-to-date manually, Polypaudio can do that automatically for you: + * if PA_STREAM_AUTO_TIMING_UPDATE is passed when connecting the + * stream Polypaudio will automatically update the structure every + * 100ms and every time a function is called that might invalidate the + * previously known timing data (such as pa_stream_write() or + * pa_stream_flush()). Please note however, that there always is a + * short time window when the data in the timing information structure + * is out-of-date. Polypaudio tries to mark these situations by + * setting the write_index_corrupt and read_index_corrupt fields + * accordingly. * - * The latency information is constantly updated from the server. Be aware - * that between updates, old data will be returned. If you specify the flag - * PA_STREAM_INTERPOLATE_TIMING when creating the stream, pa_stream_get_time() - * and pa_stream_get_latency() will calculate the latency between updates - * based on the time elapsed. + * The raw timing data in the pa_timing_info structure is usually hard + * to deal with. Therefore a more simplistic interface is available: + * you can call pa_stream_get_time() or pa_stream_get_latency(). The + * former will return the current playback time of the hardware since + * the stream has been started. The latter returns the time a sample + * that you write now takes to be played by the hardware. * + * Since updating the timing info structure usually requires a full + * round trip and some applications monitor the timing very often + * Polypaudio offers a timing interpolation system. If + * PA_STREAM_INTERPOLATE_TIMING is passed when connecting the stream, + * pa_stream_get_time() and pa_stream_get_latency() will try to + * interpolate the current playback time/latency by estimating the + * number of samples that have been played back by the hardware since + * the last regular timing update. It is espcially useful to combine + * this option with PA_STREAM_AUTO_TIMING_UPDATE, which will enable + * you to monitor the current playback time/latency very precisely + * without requiring a network round trip every time. + * * \section flow_sec Overflow and underflow * - * Even with the best precautions, buffers will sometime over- or underflow. + * Even with the best precautions, buffers will sometime over - or underflow. * To handle this gracefully, the application can be notified when this * happens. Callbacks are registered using pa_stream_set_overflow_callback() * and pa_stream_set_underflow_callback(). * + * \section sync_streams Sychronizing Multiple Playback Streams. + * + * Polypaudio allows applications to fully synchronize multiple playback + * streams that are connected to the same output device. That means + * the streams will always be played back sample-by-sample + * synchronously. If stream operations like pa_stream_cork() are + * issued on one of the synchronized streams, they are simultaneously + * issued on the others. + * + * To synchronize a stream to another, just pass the "master" stream + * as last argument to pa_stream_connect_playack(). To make sure that + * the freshly created stream doesn't start playback right-away, make + * sure to pass PA_STREAM_START_CORKED and - after all streams have + * been created - uncork them all with a single call to + * pa_stream_cork() for the master stream. + * + * To make sure that a particular stream doesn't stop to play when a + * server side buffer underrun happens on it while the other + * synchronized streams continue playing and hence deviate you need to + * pass a "prebuf" pa_buffer_attr of 0 when connecting it. + * + * \section seek_modes Seeking in the Playback Buffer + * + * T.B.D * \section disc_sec Disconnecting * * When a stream has served is purpose it must be disconnected with * pa_stream_disconnect(). If you only unreference it, then it will live on * and eat resources both locally and on the server until you disconnect the * context. + * */ /** \file |