diff options
| -rw-r--r-- | media/audio/linux/alsa_output.cc | 50 |
1 files changed, 34 insertions, 16 deletions
diff --git a/media/audio/linux/alsa_output.cc b/media/audio/linux/alsa_output.cc index 91b1efd..3086853 100644 --- a/media/audio/linux/alsa_output.cc +++ b/media/audio/linux/alsa_output.cc @@ -58,6 +58,9 @@ // busy looping. static const uint32 kNoDataSleepMilliseconds = 10; +// Mininum interval between OnMoreData() calls. +const uint32 kMinIntervalBetweenOnMoreDataCallsInMs = 5; + // According to the linux nanosleep manpage, nanosleep on linux can miss the // deadline by up to 10ms because the kernel timeslice is 10ms. Give a 2x // buffer to compensate for the timeslice, and any additional slowdowns. @@ -347,7 +350,8 @@ void AlsaPcmOutputStream::OpenTask() { if (error < 0) { LOG(ERROR) << "Failed to get playback buffer size from ALSA: " << wrapper_->StrError(error); - alsa_buffer_frames_ = frames_per_packet_; + // Buffer size is at least twice of packet size. + alsa_buffer_frames_ = frames_per_packet_ * 2; } else { alsa_buffer_frames_ = buffer_size; } @@ -427,8 +431,9 @@ void AlsaPcmOutputStream::BufferPacket(bool* source_exhausted) { *source_exhausted = false; - // Request more data if we have capacity. - if (buffer_->forward_capacity() > buffer_->forward_bytes()) { + // Request more data only when we run out of data in the buffer, because + // WritePacket() comsumes only the current chunk of data. + if (!buffer_->forward_bytes()) { // Before making a request to source for data we need to determine the // delay (in bytes) for the requested data to be played. @@ -597,25 +602,38 @@ void AlsaPcmOutputStream::ScheduleNextWrite(bool source_exhausted) { return; } - // Next write is scheduled for the moment when half of the buffer is - // available. uint32 frames_avail_wanted = alsa_buffer_frames_ / 2; uint32 available_frames = GetAvailableFrames(); - uint32 next_fill_time_ms = 0; + uint32 frames_in_buffer = buffer_->forward_bytes() / bytes_per_output_frame_; - // It's possible to have more frames available than what we want, in which - // case we'll leave our |next_fill_time_ms| at 0ms. - if (available_frames < frames_avail_wanted) { - uint32 frames_until_empty_enough = frames_avail_wanted - available_frames; - next_fill_time_ms = - FramesToMillis(frames_until_empty_enough, sample_rate_); - } + // Next write is initially scheduled for the moment when half of a packet + // has been played out. + uint32 next_fill_time_ms = + FramesToMillis(frames_per_packet_ / 2, sample_rate_); - // Adjust for timer resolution issues. - if (next_fill_time_ms < kSleepErrorMilliseconds) { + if (frames_in_buffer && (frames_in_buffer <= available_frames)) { + // There is data in the current buffer, consume them immediately if we have + // enough space in the soundcard. next_fill_time_ms = 0; } else { - next_fill_time_ms -= kSleepErrorMilliseconds; + // Otherwise schedule the next write for the moment when half of the alsa + // buffer becomes available. + if (available_frames < frames_avail_wanted) { + uint32 frames_until_empty_enough = frames_avail_wanted - available_frames; + next_fill_time_ms = + FramesToMillis(frames_until_empty_enough, sample_rate_); + + // Adjust for time resolution. + if (next_fill_time_ms > kNoDataSleepMilliseconds) + next_fill_time_ms -= kNoDataSleepMilliseconds; + + // Avoid back-to-back writing. + if (next_fill_time_ms < kMinIntervalBetweenOnMoreDataCallsInMs) + next_fill_time_ms = kMinIntervalBetweenOnMoreDataCallsInMs; + } else if (available_frames == alsa_buffer_frames_) { + // Buffer is empty, invoke next write immediately. + next_fill_time_ms = 0; + } } // Avoid busy looping if the data source is exhausted. |