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btstack_audio_portaudio: minimal volume control by multiplying samples with volume^4

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This commit is contained in:
Matthias Ringwald 2020-06-26 17:40:30 +02:00
parent d61f20b9c8
commit 1a551b1b77
1 changed files with 27 additions and 6 deletions
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33
platform/posix/btstack_audio_portaudio.c
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@ -55,7 +55,8 @@
#include <portaudio.h>
// config
static int num_channels;
static int num_channels_sink;
static int num_channels_source;
static int num_bytes_per_sample_sink;
static int num_bytes_per_sample_source;
@ -68,6 +69,8 @@ static int sink_initialized;
static int source_active;
static int sink_active;
static uint8_t sink_volume;
static PaStream * stream_source;
static PaStream * stream_sink;
@ -110,8 +113,25 @@ static int portaudio_callback_sink( const void * inputBuffer
(void) samples_per_buffer;
(void) inputBuffer;
// fill from one of our buffers
memcpy(outputBuffer, output_buffers[output_buffer_to_play], NUM_FRAMES_PER_PA_BUFFER * num_bytes_per_sample_sink);
// simplified volume control
uint16_t index;
int16_t * from_buffer = output_buffers[output_buffer_to_play];
int16_t * to_buffer = (int16_t *) outputBuffer;
#if 0
// up to 8 right shifts
int right_shift = 8 - btstack_min(8, ((sink_volume + 15) / 16));
for (index = 0; index < (NUM_FRAMES_PER_PA_BUFFER * num_channels_sink); index++){
*to_buffer++ = (*from_buffer++) >> right_shift;
}
#else
// multiply with volume ^ 4
int16_t x2 = sink_volume * sink_volume;
int16_t x4 = (x2 * x2) >> 14;
for (index = 0; index < (NUM_FRAMES_PER_PA_BUFFER * num_channels_sink); index++){
*to_buffer++ = ((*from_buffer++) * x4) >> 14;
}
#endif
// next
output_buffer_to_play = (output_buffer_to_play + 1 ) % NUM_OUTPUT_BUFFERS;
@ -181,7 +201,7 @@ static int btstack_audio_portaudio_sink_init(
){
PaError err;
num_channels = channels;
num_channels_sink = channels;
num_bytes_per_sample_sink = 2 * channels;
if (!playback){
@ -234,6 +254,7 @@ static int btstack_audio_portaudio_sink_init(
playback_callback = playback;
sink_initialized = 1;
sink_volume = 127;
return 0;
}
@ -245,7 +266,7 @@ static int btstack_audio_portaudio_source_init(
){
PaError err;
num_channels = channels;
num_channels_source = channels;
num_bytes_per_sample_source = 2 * channels;
if (!recording){
@ -303,7 +324,7 @@ static int btstack_audio_portaudio_source_init(
}
static void btstack_audio_portaudio_sink_set_volume(uint8_t volume){
UNUSED(volume);
sink_volume = volume;
}
static void btstack_audio_portaudio_source_set_gain(uint8_t gain){