Return-Path: From: Andrzej Kaczmarek To: CC: Andrzej Kaczmarek Subject: [PATCH v3] android/hal-audio: Add simple downmix to mono Date: Tue, 4 Feb 2014 14:38:45 +0100 Message-ID: <1391521125-2465-1-git-send-email-andrzej.kaczmarek@tieto.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-bluetooth-owner@vger.kernel.org List-ID: This patch adds simple downmix support from stereo to mono in order to support mono channel mode as it's mandatory for SBC codec. It uses simple (L+R)/2 calculation which should be good enough. --- android/hal-audio.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 49 insertions(+), 5 deletions(-) diff --git a/android/hal-audio.c b/android/hal-audio.c index efdf823..f90265b 100644 --- a/android/hal-audio.c +++ b/android/hal-audio.c @@ -36,9 +36,12 @@ #include "hal-log.h" #include "hal-msg.h" #include "../profiles/audio/a2dp-codecs.h" +#include "../src/shared/util.h" #define FIXED_A2DP_PLAYBACK_LATENCY_MS 25 +#define FIXED_BUFFER_SIZE (20 * 512) + #define MAX_FRAMES_IN_PAYLOAD 15 static const uint8_t a2dp_src_uuid[] = { @@ -220,6 +223,8 @@ struct a2dp_stream_out { struct audio_endpoint *ep; enum a2dp_state_t audio_state; struct audio_input_config cfg; + + uint8_t *downmix_buf; }; struct a2dp_audio_dev { @@ -230,7 +235,8 @@ struct a2dp_audio_dev { static const a2dp_sbc_t sbc_presets[] = { { .frequency = SBC_SAMPLING_FREQ_44100 | SBC_SAMPLING_FREQ_48000, - .channel_mode = SBC_CHANNEL_MODE_DUAL_CHANNEL | + .channel_mode = SBC_CHANNEL_MODE_MONO | + SBC_CHANNEL_MODE_DUAL_CHANNEL | SBC_CHANNEL_MODE_STEREO | SBC_CHANNEL_MODE_JOINT_STEREO, .subbands = SBC_SUBBANDS_4 | SBC_SUBBANDS_8, @@ -826,6 +832,21 @@ static void unregister_endpoints(void) } } +static void downmix_to_mono(struct a2dp_stream_out *out, const uint8_t *buffer, + size_t bytes) +{ + const int16_t *input = (const void *) buffer; + int16_t *output = (void *) out->downmix_buf; + size_t i; + + for (i = 0; i < bytes / 2; i++) { + int16_t l = le16_to_cpu(get_unaligned(&input[i * 2])); + int16_t r = le16_to_cpu(get_unaligned(&input[i * 2 + 1])); + + put_unaligned(cpu_to_le16((l + r) / 2), &output[i]); + } +} + static ssize_t out_write(struct audio_stream_out *stream, const void *buffer, size_t bytes) { @@ -853,6 +874,18 @@ static ssize_t out_write(struct audio_stream_out *stream, const void *buffer, return -1; } + if (out->cfg.channels == AUDIO_CHANNEL_OUT_MONO) { + if (!out->downmix_buf) { + error("audio: downmix buffer not initialized"); + return -1; + } + + downmix_to_mono(out, buffer, bytes); + + return out->ep->codec->write_data(out->ep->codec_data, + out->downmix_buf, bytes / 2, out->ep->fd) * 2; + } + return out->ep->codec->write_data(out->ep->codec_data, buffer, bytes, out->ep->fd); } @@ -890,16 +923,18 @@ static size_t out_get_buffer_size(const struct audio_stream *stream) * use magic value here and out_write code takes care of splitting * input buffer into multiple media packets. */ - return 20 * 512; + return FIXED_BUFFER_SIZE; } static uint32_t out_get_channels(const struct audio_stream *stream) { - struct a2dp_stream_out *out = (struct a2dp_stream_out *) stream; - DBG(""); - return out->cfg.channels; + /* AudioFlinger can only provide stereo stream, so we return it here and + * later we'll downmix this to mono in case codec requires it + */ + + return AUDIO_CHANNEL_OUT_STEREO; } static audio_format_t out_get_format(const struct audio_stream *stream) @@ -1212,6 +1247,12 @@ static int audio_open_output_stream(struct audio_hw_device *dev, free(preset); + if (out->cfg.channels == AUDIO_CHANNEL_OUT_MONO) { + out->downmix_buf = malloc(FIXED_BUFFER_SIZE / 2); + if (!out->downmix_buf) + goto fail; + } + *stream_out = &out->stream; a2dp_dev->out = out; @@ -1230,6 +1271,7 @@ static void audio_close_output_stream(struct audio_hw_device *dev, struct audio_stream_out *stream) { struct a2dp_audio_dev *a2dp_dev = (struct a2dp_audio_dev *) dev; + struct a2dp_stream_out *out = (struct a2dp_stream_out *) stream; struct audio_endpoint *ep = a2dp_dev->out->ep; DBG(""); @@ -1243,6 +1285,8 @@ static void audio_close_output_stream(struct audio_hw_device *dev, ep->codec->cleanup(ep->codec_data); ep->codec_data = NULL; + free(out->downmix_buf); + free(stream); a2dp_dev->out = NULL; } -- 1.8.5.3