PulseAudioasynchronous库如何用于播放原始PCM数据?

PulseAudio文档似乎没有一个明确的解释,我找不到任何简单的例子。

像这样

/* pcm-playback: pcm-playback.c gcc -o pcm-playback pcm-playback.c `pkg-config --cflags --libs libpulse` */ #include <stdio.h> #include <assert.h> #include <pulse/pulseaudio.h> #define FORMAT PA_SAMPLE_U8 #define RATE 44100 void context_state_cb(pa_context* context, void* mainloop); void stream_state_cb(pa_stream *s, void *mainloop); void stream_success_cb(pa_stream *stream, int success, void *userdata); void stream_write_cb(pa_stream *stream, size_t requested_bytes, void *userdata); int main(int argc, char *argv[]) { pa_threaded_mainloop *mainloop; pa_mainloop_api *mainloop_api; pa_context *context; pa_stream *stream; // Get a mainloop and its context mainloop = pa_threaded_mainloop_new(); assert(mainloop); mainloop_api = pa_threaded_mainloop_get_api(mainloop); context = pa_context_new(mainloop_api, "pcm-playback"); assert(context); // Set a callback so we can wait for the context to be ready pa_context_set_state_callback(context, &context_state_cb, mainloop); // Lock the mainloop so that it does not run and crash before the context is ready pa_threaded_mainloop_lock(mainloop); // Start the mainloop assert(pa_threaded_mainloop_start(mainloop) == 0); assert(pa_context_connect(context, NULL, PA_CONTEXT_NOAUTOSPAWN, NULL) == 0); // Wait for the context to be ready for(;;) { pa_context_state_t context_state = pa_context_get_state(context); assert(PA_CONTEXT_IS_GOOD(context_state)); if (context_state == PA_CONTEXT_READY) break; pa_threaded_mainloop_wait(mainloop); } // Create a playback stream pa_sample_spec sample_specifications; sample_specifications.format = FORMAT; sample_specifications.rate = RATE; sample_specifications.channels = 2; pa_channel_map map; pa_channel_map_init_stereo(&map); stream = pa_stream_new(context, "Playback", &sample_specifications, &map); pa_stream_set_state_callback(stream, stream_state_cb, mainloop); pa_stream_set_write_callback(stream, stream_write_cb, mainloop); // recommended settings, ie server uses sensible values pa_buffer_attr buffer_attr; buffer_attr.maxlength = (uint32_t) -1; buffer_attr.tlength = (uint32_t) -1; buffer_attr.prebuf = (uint32_t) -1; buffer_attr.minreq = (uint32_t) -1; // Settings copied as per the chromium browser source pa_stream_flags_t stream_flags; stream_flags = PA_STREAM_START_CORKED | PA_STREAM_INTERPOLATE_TIMING | PA_STREAM_NOT_MONOTONIC | PA_STREAM_AUTO_TIMING_UPDATE | PA_STREAM_ADJUST_LATENCY; // Connect stream to the default audio output sink assert(pa_stream_connect_playback(stream, NULL, &buffer_attr, stream_flags, NULL, NULL) == 0); // Wait for the stream to be ready for(;;) { pa_stream_state_t stream_state = pa_stream_get_state(stream); assert(PA_STREAM_IS_GOOD(stream_state)); if (stream_state == PA_STREAM_READY) break; pa_threaded_mainloop_wait(mainloop); } pa_threaded_mainloop_unlock(mainloop); // Uncork the stream so it will start playing pa_stream_cork(stream, 0, stream_success_cb, mainloop); // Play until we get a character getc(stdin); } void context_state_cb(pa_context* context, void* mainloop) { pa_threaded_mainloop_signal(mainloop, 0); } void stream_state_cb(pa_stream *s, void *mainloop) { pa_threaded_mainloop_signal(mainloop, 0); } void stream_write_cb(pa_stream *stream, size_t requested_bytes, void *userdata) { int bytes_remaining = requested_bytes; while (bytes_remaining > 0) { uint8_t *buffer = NULL; size_t bytes_to_fill = 44100; size_t i; if (bytes_to_fill > bytes_remaining) bytes_to_fill = bytes_remaining; pa_stream_begin_write(stream, (void**) &buffer, &bytes_to_fill); for (i = 0; i < bytes_to_fill; i += 2) { buffer[i] = (i%100) * 40 / 100 + 44; buffer[i+1] = (i%100) * 40 / 100 + 44; } pa_stream_write(stream, buffer, bytes_to_fill, NULL, 0LL, PA_SEEK_RELATIVE); bytes_remaining -= bytes_to_fill; } } void stream_success_cb(pa_stream *stream, int success, void *userdata) { return; }