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Commit 0abb6143 authored by Pavlin Radoslavov's avatar Pavlin Radoslavov
Browse files

Add a workaround to play A2DP SBC Mono 

The PCM audio is pulled as STEREO and mixed into MONO by the
Audio A2DP HAL.

Test: Playing SBC mono with Headset
Bug: 67763743
Change-Id: I2710a6633dd81c6917362ed6dd4af75a8d517b0a
parent 76401924

system/audio_a2dp_hw/src/audio_a2dp_hw.cc

+31 −2
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ struct a2dp_audio_device { 
struct a2dp_config {

  uint32_t rate;

  uint32_t channel_mask;

  bool is_stereo_to_mono;  // True if fetching Stereo and mixing into Mono

  int format;

};
@@ -591,24 +592,34 @@ static int a2dp_read_output_audio_config( 
  switch (codec_config->channel_mode) {

    case BTAV_A2DP_CODEC_CHANNEL_MODE_MONO:

      stream_config.channel_mask = AUDIO_CHANNEL_OUT_MONO;

      stream_config.is_stereo_to_mono = true;

      break;

    case BTAV_A2DP_CODEC_CHANNEL_MODE_STEREO:

      stream_config.channel_mask = AUDIO_CHANNEL_OUT_STEREO;

      stream_config.is_stereo_to_mono = false;

      break;

    case BTAV_A2DP_CODEC_CHANNEL_MODE_NONE:

    default:

      ERROR("Invalid channel mode: 0x%x", codec_config->channel_mode);

      return -1;

  }

  if (stream_config.is_stereo_to_mono) {

    stream_config.channel_mask = AUDIO_CHANNEL_OUT_STEREO;

  }



  // Update the output stream configuration

  if (update_stream_config) {

    common->cfg.rate = stream_config.rate;

    common->cfg.channel_mask = stream_config.channel_mask;

    common->cfg.is_stereo_to_mono = stream_config.is_stereo_to_mono;

    common->cfg.format = stream_config.format;

    common->buffer_sz = audio_a2dp_hw_stream_compute_buffer_size(

        codec_config->sample_rate, codec_config->bits_per_sample,

        codec_config->channel_mode);

    if (common->cfg.is_stereo_to_mono) {

      // We need to fetch twice as much data from the Audio framework

      common->buffer_sz *= 2;

    }

  }



  INFO(
@@ -679,7 +690,11 @@ static int a2dp_write_output_audio_config(struct a2dp_stream_common* common) { 
      codec_config.channel_mode = BTAV_A2DP_CODEC_CHANNEL_MODE_MONO;

      break;

    case AUDIO_CHANNEL_OUT_STEREO:

      if (common->cfg.is_stereo_to_mono) {

        codec_config.channel_mode = BTAV_A2DP_CODEC_CHANNEL_MODE_MONO;

      } else {

        codec_config.channel_mode = BTAV_A2DP_CODEC_CHANNEL_MODE_STEREO;

      }

      break;

    default:

      ERROR("Invalid channel mask: 0x%x", common->cfg.channel_mask);
@@ -844,6 +859,7 @@ static ssize_t out_write(struct audio_stream_out* stream, const void* buffer, 
                         size_t bytes) {

  struct a2dp_stream_out* out = (struct a2dp_stream_out*)stream;

  int sent = -1;

  size_t write_bytes = bytes;



  DEBUG("write %zu bytes (fd %d)", bytes, out->common.audio_fd);
@@ -865,8 +881,21 @@ static ssize_t out_write(struct audio_stream_out* stream, const void* buffer, 
    goto finish;

  }



  // Mix the stereo into mono if necessary

  if (out->common.cfg.is_stereo_to_mono) {

    const size_t frames = bytes / audio_stream_out_frame_size(stream);

    int16_t* src = (int16_t*)buffer;

    int16_t* dst = (int16_t*)buffer;

    for (size_t i = 0; i < frames; i++, dst++, src += 2) {

      *dst = (int16_t)(((int32_t)src[0] + (int32_t)src[1]) >> 1);

    }

    write_bytes /= 2;

    DEBUG("stereo-to-mono mixing: write %zu bytes (fd %d)", write_bytes,

          out->common.audio_fd);

  }



  lock.unlock();

  sent = skt_write(out->common.audio_fd, buffer, bytes);

  sent = skt_write(out->common.audio_fd, buffer, write_bytes);

  lock.lock();



  if (sent == -1) {