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firpfbch: enhanced the channelizer to support user-defined decimate delays #406

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firpfbch: enhanced the channelizer to support user-defined decimate delays #406

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325a5a5
firpfbch: enhanced the channelizer to support user-defined delays
noonafter May 25, 2025
abf5270
1. change (_set_chan_delay) to (_set_decimate_delay), preventing conf…
noonafter Jun 5, 2025
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3 changes: 3 additions & 0 deletions include/liquid.h
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Original file line number Diff line number Diff line change
Expand Up @@ -8782,6 +8782,9 @@ int FIRPFBCH(_destroy)(FIRPFBCH() _q); \
/* Clear/reset firpfbch internal state */ \
int FIRPFBCH(_reset)(FIRPFBCH() _q); \
\
/* Set the delay of channelizer decimator */ \
int FIRPFBCH(_set_decimate_delay)(FIRPFBCH() _q, unsigned int _d); \
\
/* Print firpfbch internal parameters to stdout */ \
int FIRPFBCH(_print)(FIRPFBCH() _q); \
\
Expand Down
84 changes: 55 additions & 29 deletions src/multichannel/src/firpfbch.proto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@
// firpfbch object structure definition
struct FIRPFBCH(_s) {
int type; // synthesis/analysis
unsigned int num_channels; // number of channels
unsigned int M; // number of channels
unsigned int p; // filter length (symbols)

// filter
Expand All @@ -43,6 +43,7 @@ struct FIRPFBCH(_s) {
DOTPROD() * dp; // dot product object array
WINDOW() * w; // window buffer object array
unsigned int filter_index; // running filter index (analysis)
unsigned int initial_index; // initial filter index (complementary to decimator delay)

// fft plan
FFT_PLAN fft; // fft|ifft object
Expand Down Expand Up @@ -83,16 +84,16 @@ FIRPFBCH() FIRPFBCH(_create)(int _type,
FIRPFBCH() q = (FIRPFBCH()) malloc(sizeof(struct FIRPFBCH(_s)));

// set user-defined properties
q->type = _type;
q->num_channels = _M;
q->p = _p;
q->type = _type;
q->M = _M;
q->p = _p;

// derived values
q->h_len = q->num_channels * q->p;
q->h_len = q->M * q->p;

// create bank of filters
q->dp = (DOTPROD()*) malloc((q->num_channels)*sizeof(DOTPROD()));
q->w = (WINDOW()*) malloc((q->num_channels)*sizeof(WINDOW()));
q->dp = (DOTPROD()*) malloc((q->M)*sizeof(DOTPROD()));
q->w = (WINDOW()*) malloc((q->M)*sizeof(WINDOW()));

// copy filter coefficients
q->h = (TC*) malloc((q->h_len)*sizeof(TC));
Expand All @@ -104,10 +105,10 @@ FIRPFBCH() FIRPFBCH(_create)(int _type,
unsigned int n;
unsigned int h_sub_len = q->p;
TC h_sub[h_sub_len];
for (i=0; i<q->num_channels; i++) {
for (i=0; i<q->M; i++) {
// sub-sample prototype filter, loading coefficients in reverse order
for (n=0; n<h_sub_len; n++) {
h_sub[h_sub_len-n-1] = q->h[i + n*(q->num_channels)];
h_sub[h_sub_len-n-1] = q->h[i + n*(q->M)];
}
// create window buffer and dotprod object (coefficients
// loaded in reverse order)
Expand All @@ -116,16 +117,19 @@ FIRPFBCH() FIRPFBCH(_create)(int _type,
}

// allocate memory for buffers
q->x = (T*) FFT_MALLOC((q->num_channels)*sizeof(T));
q->X = (T*) FFT_MALLOC((q->num_channels)*sizeof(T));
q->x = (T*) FFT_MALLOC((q->M)*sizeof(T));
q->X = (T*) FFT_MALLOC((q->M)*sizeof(T));

// create fft plan
if (q->type == LIQUID_ANALYZER)
q->fft = FFT_CREATE_PLAN(q->num_channels, q->X, q->x, FFT_DIR_FORWARD, FFT_METHOD);
q->fft = FFT_CREATE_PLAN(q->M, q->X, q->x, FFT_DIR_FORWARD, FFT_METHOD);
else
q->fft = FFT_CREATE_PLAN(q->num_channels, q->X, q->x, FFT_DIR_BACKWARD, FFT_METHOD);
q->fft = FFT_CREATE_PLAN(q->M, q->X, q->x, FFT_DIR_BACKWARD, FFT_METHOD);

// reset filterbank object
// set default initial index to M-1(i.e. default delay is 1)for backward compatibility with previous versions
// or alternatively set it to 0 to align with MATLAB's DSP toolbox
q->initial_index = q->M-1;
FIRPFBCH(_reset)(q);

// return filterbank object
Expand Down Expand Up @@ -227,7 +231,7 @@ int FIRPFBCH(_destroy)(FIRPFBCH() _q)
unsigned int i;

// free dot product, window objects and arrays
for (i=0; i<_q->num_channels; i++) {
for (i=0; i<_q->M; i++) {
DOTPROD(_destroy)(_q->dp[i]);
WINDOW(_destroy)(_q->w[i]);
}
Expand All @@ -251,21 +255,35 @@ int FIRPFBCH(_destroy)(FIRPFBCH() _q)
int FIRPFBCH(_reset)(FIRPFBCH() _q)
{
unsigned int i;
for (i=0; i<_q->num_channels; i++) {
for (i=0; i<_q->M; i++) {
WINDOW(_reset)(_q->w[i]);
_q->x[i] = 0;
_q->X[i] = 0;
}
_q->filter_index = _q->num_channels-1;
_q->filter_index = _q->initial_index;
return LIQUID_OK;
}

// Set the delay of decimator, which is complementary to initial_index
// _q : firpfbch object
// _d : delay of channelizer
int FIRPFBCH(_set_decimate_delay)(FIRPFBCH() _q, unsigned int _d)
{
// wrap _d into valid range
_d = _d % _q->M;

_q->initial_index = _d == 0 ? 0 : _q->M - _d;
_q->filter_index = _q->initial_index;
return LIQUID_OK;
}


// print firpfbch object
int FIRPFBCH(_print)(FIRPFBCH() _q)
{
printf("<liquid.firpfbch, type=\"%s\", channels=%u, semilen=%u>\n",
_q->type == LIQUID_ANALYZER ? "analyzer" : "synthesizer",
_q->num_channels, _q->p);
_q->M, _q->p);
return LIQUID_OK;
}

Expand All @@ -284,15 +302,15 @@ int FIRPFBCH(_synthesizer_execute)(FIRPFBCH() _q,
unsigned int i;

// copy channelized symbols to transform input
memmove(_q->X, _x, _q->num_channels*sizeof(TI));
memmove(_q->X, _x, _q->M*sizeof(TI));

// execute inverse DFT, store result in buffer 'x'
FFT_EXECUTE(_q->fft);

// push samples into filter bank and execute
T * r; // read pointer
for (i=0; i<_q->num_channels; i++) {
WINDOW(_push)(_q->w[i], _q->x[i]);
for (i=0; i<_q->M; i++) {
WINDOW(_push)(_q->w[i], _q->x[(i+_q->initial_index+1)%_q->M]);
WINDOW(_read)(_q->w[i], &r);
DOTPROD(_execute)(_q->dp[i], r, &_y[i]);

Expand All @@ -317,12 +335,20 @@ int FIRPFBCH(_analyzer_execute)(FIRPFBCH() _q,
unsigned int i;

// push samples into buffers
for (i=0; i<_q->num_channels; i++)
for (i=0; i<_q->M; i++) {
FIRPFBCH(_analyzer_push)(_q, _x[i]);

// execute analysis filters on the given input starting
// with filterbank at index zero
return FIRPFBCH(_analyzer_run)(_q, 0, _y);
// if filters already have M samples after being pushed,
// execute analysis filters on the given input starting
// with filterbank at index zero
// Note: after the filters perform a calculation,
// the remaining points still need to be pushed into the windows
if ( _q->filter_index == _q->M-1) {
FIRPFBCH(_analyzer_run)(_q, 0, _y);
}
}

return LIQUID_OK;
}

//
Expand All @@ -340,7 +366,7 @@ int FIRPFBCH(_analyzer_push)(FIRPFBCH() _q,
WINDOW(_push)(_q->w[_q->filter_index], _x);

// decrement filter index
_q->filter_index = (_q->filter_index + _q->num_channels - 1) % _q->num_channels;
_q->filter_index = _q->filter_index == 0 ? _q->M-1 : _q->filter_index-1;
return LIQUID_OK;
}

Expand All @@ -358,22 +384,22 @@ int FIRPFBCH(_analyzer_run)(FIRPFBCH() _q,
// sure why this is necessary)
T * r; // read pointer
unsigned int index;
for (i=0; i<_q->num_channels; i++) {
for (i=0; i<_q->M; i++) {
// compute appropriate index
index = (i+_k) % _q->num_channels;
index = (i+_k) % _q->M;

// read buffer at specified index
WINDOW(_read)(_q->w[index], &r);

// compute dot product
DOTPROD(_execute)(_q->dp[i], r, &_q->X[_q->num_channels-i-1]);
DOTPROD(_execute)(_q->dp[i], r, &_q->X[(_q->initial_index+_q->M-i)%_q->M]);
}

// execute DFT, store result in buffer 'x'
FFT_EXECUTE(_q->fft);

// move to output array
memmove(_y, _q->x, _q->num_channels*sizeof(TO));
memmove(_y, _q->x, _q->M*sizeof(TO));
return LIQUID_OK;
}

14 changes: 9 additions & 5 deletions src/multichannel/tests/firpfbch_crcf_analyzer_autotest.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,8 +52,11 @@ void autotest_firpfbch_crcf_analysis()
h[i] = (float)msequence_generate_symbol(ms, 2) - 1.5f; // (-1.5, -0.5, 0.5, 1.5)
msequence_destroy(ms);

// create filterbank object
unsigned int chan_delay;
for (chan_delay = 0; chan_delay < num_channels; chan_delay++){
// create filterbank object with delay values from 0 to num_channels-1
firpfbch_crcf q = firpfbch_crcf_create(LIQUID_ANALYZER, num_channels, p, h);
firpfbch_crcf_set_decimate_delay(q, chan_delay);

// generate filter object
firfilt_crcf f = firfilt_crcf_create(h, h_len);
Expand Down Expand Up @@ -101,8 +104,8 @@ void autotest_firpfbch_crcf_analysis()
firfilt_crcf_push(f, y[j]*cexpf(-_Complex_I*j*dphi));

// compute output at the appropriate sample time
assert(n<num_symbols);
if ( ((j+1)%num_channels)==0 ) {
assert(n<=num_symbols);
if ( ((j+chan_delay)%num_channels)==0 ) {
firfilt_crcf_execute(f, &Y1[n][i]);
n++;
}
Expand All @@ -118,7 +121,7 @@ void autotest_firpfbch_crcf_analysis()
if (liquid_autotest_verbose) {
// print filterbank channelizer
printf("\n");
printf("filterbank channelizer:\n");
printf("filterbank channelizer, delay is %d:\n",chan_delay);
for (i=0; i<num_symbols; i++) {
printf("%3u: ", i);
for (j=0; j<num_channels; j++) {
Expand All @@ -129,7 +132,7 @@ void autotest_firpfbch_crcf_analysis()

// print traditional channelizer
printf("\n");
printf("traditional channelizer:\n");
printf("traditional channelizer, delay is %d:\n",chan_delay);
for (i=0; i<num_symbols; i++) {
printf("%3u: ", i);
for (j=0; j<num_channels; j++) {
Expand All @@ -146,6 +149,7 @@ void autotest_firpfbch_crcf_analysis()
CONTEND_DELTA( cimagf(Y0[i][j]), cimagf(Y1[i][j]), tol );
}
}
}

}

Expand Down