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audio scaling for pdm

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Andrew Stanford-Jason
2015-09-22 12:21:33 +01:00
parent 5adfd29c17
commit 35834c4fb8
3 changed files with 1006 additions and 506 deletions
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25
module_usb_audio/pcm_pdm_mic.xc
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@@ -27,6 +27,13 @@ typedef struct {
} synchronised_audio;
static int dc_offset_removal(int sample, int &prex_x, int &prev_y){
int r = prev_y- (prev_y>>5) + (sample - prex_x);
prex_x = sample;
prev_y = r;
return r;
}
void example(streaming chanend c_ds_output_0, streaming chanend c_ds_output_1, streaming chanend c_pcm_out)
{
@@ -35,6 +42,8 @@ void example(streaming chanend c_ds_output_0, streaming chanend c_ds_output_1, s
synchronised_audio audio[2]; //double buffered
memset(audio, sizeof(synchronised_audio), 2);
int prev_x[7] = {0};
int prev_y[7] = {0};
unsafe
{
@@ -52,15 +61,17 @@ void example(streaming chanend c_ds_output_0, streaming chanend c_ds_output_1, s
buffer = 1 - buffer;
//The data has already been bit reversed in the downsampler
// audio[buffer] is good to go
//xscope_int(0, audio[buffer].data[0][0].ch_a);
//xscope_int(1, audio[buffer].data[0][0].ch_b);
int a = dc_offset_removal( audio[buffer].data[1][0].ch_a, prev_x[0], prev_y[0]);
int b = dc_offset_removal( audio[buffer].data[1][0].ch_b, prev_x[1], prev_y[1]);
xscope_int(0,a);
xscope_int(1,b);
c_pcm_out :> unsigned req;
c_pcm_out <: audio[buffer].data[0][0].ch_a;
c_pcm_out <: audio[buffer].data[0][0].ch_b;
//printintln(audio[buffer].data[0][0].ch_b);
c_pcm_out <: (a>>14);
c_pcm_out <: (b>>14);
}
}
}