diff options
| -rw-r--r-- | src/cubeb_aaudio.cpp | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/src/cubeb_aaudio.cpp b/src/cubeb_aaudio.cpp index 94133ab..cea48d5 100644 --- a/src/cubeb_aaudio.cpp +++ b/src/cubeb_aaudio.cpp @@ -9,6 +9,7 @@ #include "cubeb_android.h" #include "cubeb_log.h" #include "cubeb_resampler.h" +#include "cubeb_triple_buffer.h" #include <aaudio/AAudio.h> #include <atomic> #include <cassert> @@ -114,6 +115,15 @@ enum class stream_state { SHUTDOWN, }; +struct AAudioTimingInfo { + // The number of frames sent to the engine. + uint64_t frame_index; + // The timestamp at which the audio engine last called the calback. + uint64_t tstamp; + // The current output latency in frames. + uint32_t latency; +}; + struct cubeb_stream { /* Note: Must match cubeb_stream layout in cubeb.c. */ cubeb * context{}; @@ -121,6 +131,7 @@ struct cubeb_stream { std::atomic<bool> in_use{false}; std::atomic<stream_state> state{stream_state::INIT}; + triple_buffer<AAudioTimingInfo> timing_info; AAudioStream * ostream{}; AAudioStream * istream{}; @@ -593,6 +604,55 @@ aaudio_duplex_data_cb(AAudioStream * astream, void * user_data, return AAUDIO_CALLBACK_RESULT_CONTINUE; } +uint64_t +now_ns() +{ + using namespace std::chrono; + return duration_cast<nanoseconds>(steady_clock::now().time_since_epoch()) + .count(); +} + +// To be called from the real-time audio callback +uint64_t +aaudio_get_latency(cubeb_stream * stm, aaudio_direction_t direction, + uint64_t tstamp_ns) +{ + bool is_output = direction == AAUDIO_DIRECTION_OUTPUT; + int64_t hw_frame_index; + int64_t hw_tstamp; + AAudioStream * stream = is_output ? stm->ostream : stm->istream; + // For an output stream (resp. input stream), get the number of frames + // written to (resp read from) the hardware. + int64_t app_frame_index = is_output + ? WRAP(AAudioStream_getFramesWritten)(stream) + : WRAP(AAudioStream_getFramesRead)(stream); + + // Get a timestamp for a particular frame index written to or read from the + // hardware. + auto result = WRAP(AAudioStream_getTimestamp)(stream, CLOCK_MONOTONIC, + &hw_frame_index, &hw_tstamp); + if (result != AAUDIO_OK) { + LOG("AAudioStream_getTimestamp failure."); + return 0; + } + + // Compute the difference between the app and the hardware indices. + int64_t frame_index_delta = app_frame_index - hw_frame_index; + // Convert to ns + int64_t frame_time_delta = (frame_index_delta * 1e9) / stm->sample_rate; + // Extrapolate from the known timestamp for a particular frame presented. + int64_t app_frame_hw_time = hw_tstamp + frame_time_delta; + // For an output stream, the latency is positive, for an input stream, it's + // negative. + int64_t latency_ns = + is_output ? app_frame_hw_time - tstamp_ns : tstamp_ns - app_frame_hw_time; + int64_t latency_frames = stm->sample_rate * latency_ns / 1e9; + + LOGV("Latency in frames: %d (%dms)", latency_frames, latency_ns / 1e6); + + return latency_frames; +} + static aaudio_data_callback_result_t aaudio_output_data_cb(AAudioStream * astream, void * user_data, void * audio_data, int32_t num_frames) @@ -619,6 +679,17 @@ aaudio_output_data_cb(AAudioStream * astream, void * user_data, return AAUDIO_CALLBACK_RESULT_CONTINUE; } + uint64_t tstamp_ns = now_ns(); + uint64_t latency_frames = + aaudio_get_latency(stm, AAUDIO_DIRECTION_OUTPUT, tstamp_ns); + if (latency_frames != 0) { + AAudioTimingInfo info; + info.tstamp = tstamp_ns; + info.latency = latency_frames; + info.frame_index = WRAP(AAudioStream_getFramesWritten)(stm->ostream); + stm->timing_info.write(info); + } + long done_frames = cubeb_resampler_fill(stm->resampler, NULL, NULL, audio_data, num_frames); if (done_frames < 0 || done_frames > num_frames) { |