GNU Radio 3.6.4.2 C++ API
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Polyphase filterbank arbitrary resampler with float input, float output and float taps. More...
#include <gr_pfb_arb_resampler_fff.h>
Public Member Functions | |
~gr_pfb_arb_resampler_fff () | |
void | print_taps () |
void | set_rate (float rate) |
int | general_work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) |
compute output items from input items More... | |
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gr_block (void) | |
gr_block (const std::string &name, gr_io_signature_sptr input_signature, gr_io_signature_sptr output_signature) | |
long | unique_id (void) const |
std::string | name (void) const |
virtual | ~gr_block (void) |
gr_io_signature_sptr | input_signature (void) const |
gr_io_signature_sptr | output_signature (void) const |
void | set_input_signature (gr_io_signature_sptr sig) |
void | set_output_signature (gr_io_signature_sptr sig) |
virtual bool | check_topology (int ninputs, int noutputs) |
virtual void | forecast (int, std::vector< int > &) |
Overload me! I am the forecast. More... | |
virtual bool | start (void) |
virtual bool | stop (void) |
void | consume_each (const int how_many_items) |
Call during work to consume items. More... | |
void | consume (const size_t i, const int how_many_items) |
void | produce (const size_t o, const int how_many_items) |
uint64_t | nitems_read (const size_t which_input=0) |
Get absolute count of all items consumed on the given input port. More... | |
uint64_t | nitems_written (const size_t which_output=0) |
Get absolute count of all items produced on the given output port. More... | |
void | add_item_tag (const size_t which_output, const gr_tag_t &tag) |
void | add_item_tag (const size_t which_output, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F) |
void | get_tags_in_range (std::vector< gr_tag_t > &tags, const size_t which_input, uint64_t abs_start, uint64_t abs_end, const pmt::pmt_t &key=pmt::pmt_t()) |
void | set_alignment (const size_t alignment) |
bool | is_unaligned (void) |
size_t | fixed_rate_noutput_to_ninput (const size_t noutput_items) |
size_t | interpolation (void) const |
void | set_interpolation (const size_t) |
size_t | decimation (void) const |
void | set_decimation (const size_t) |
int | max_noutput_items (void) const |
void | set_max_noutput_items (int) |
void | unset_max_noutput_items (void) |
bool | is_set_max_noutput_items (void) const |
unsigned | history (void) const |
void | set_history (unsigned history) |
void | set_fixed_rate (const bool fixed_rate) |
bool | fixed_rate (void) const |
Get the fixed rate setting. More... | |
void | set_relative_rate (const double relative_rate) |
double | relative_rate (void) const |
Get the relative rate setting. More... | |
void | set_output_multiple (const size_t multiple) |
size_t | output_multiple (void) const |
Get the output multiple setting. More... | |
tag_propagation_policy_t | tag_propagation_policy (void) |
void | set_tag_propagation_policy (tag_propagation_policy_t p) |
void | set_max_output_buffer (long) |
void | set_max_output_buffer (int, long) |
long | max_output_buffer (size_t) |
void | set_min_output_buffer (long) |
void | set_min_output_buffer (int, long) |
long | min_output_buffer (size_t) |
std::string | symbol_name () const |
bool | alias_set () |
std::string | alias () |
pmt::pmt_t | alias_pmt () |
void | set_block_alias (std::string name) |
template<typename T > | |
void | set_msg_handler (pmt::pmt_t which_port, T msg_handler) |
void | message_port_register_in (pmt::pmt_t) |
void | message_port_register_out (pmt::pmt_t) |
void | message_port_pub (pmt::pmt_t, pmt::pmt_t) |
void | message_port_sub (pmt::pmt_t, pmt::pmt_t) |
void | message_port_unsub (pmt::pmt_t, pmt::pmt_t) |
virtual bool | message_port_is_hier (pmt::pmt_t port_id) |
virtual bool | message_port_is_hier_in (pmt::pmt_t port_id) |
virtual bool | message_port_is_hier_out (pmt::pmt_t port_id) |
pmt::pmt_t | message_ports_in () |
Get input message port names. More... | |
pmt::pmt_t | message_ports_out () |
Get output message port names. More... | |
bool | empty_p (pmt::pmt_t which_port) |
is the queue empty? More... | |
bool | empty_p () |
void | insert_tail (pmt::pmt_t, pmt::pmt_t) |
pmt::pmt_t | delete_head_nowait (pmt::pmt_t) |
pmt::pmt_t | delete_head_blocking (pmt::pmt_t) |
msg_queue_t::iterator | get_iterator (pmt::pmt_t which_port) |
void | erase_msg (pmt::pmt_t which_port, msg_queue_t::iterator it) |
virtual bool | has_msg_port (pmt::pmt_t which_port) |
bool | has_msg_handler (pmt::pmt_t which_port) |
Tests if there is a handler attached to port which_port . More... | |
virtual void | dispatch_msg (pmt::pmt_t which_port, pmt::pmt_t msg) |
void | set_processor_affinity (const std::vector< int > &mask) |
Set the thread's affinity to processor core n . More... | |
void | unset_processor_affinity () |
Remove processor affinity to a specific core. More... | |
std::vector< int > | processor_affinity () |
Get the current processor affinity. More... | |
void | work (const InputItems &, const OutputItems &) |
implements work -> calls general work More... | |
void | notify_topology (const size_t, const size_t) |
notifications of new topological commits More... | |
void | notify_active (void) |
start notification More... | |
void | notify_inactive (void) |
stop notification More... | |
virtual void | propagate_tags (const size_t, const gras::TagIter &) |
implements tag_propagation_policy() More... | |
void | _update_input_reserve (void) |
gras::BufferQueueSptr | input_buffer_allocator (const size_t, const gras::SBufferConfig &) |
gras::BufferQueueSptr | output_buffer_allocator (const size_t, const gras::SBufferConfig &) |
Friends | |
GR_CORE_API gr_pfb_arb_resampler_fff_sptr | gr_make_pfb_arb_resampler_fff (float rate, const std::vector< float > &taps, unsigned int filter_size) |
Polyphase filterbank arbitrary resampler with float input, float output and float taps.
This block takes in a signal stream and performs arbitrary resampling. The resampling rate can be any real number r. The resampling is done by constructing N filters where N is the interpolation rate. We then calculate D where D = floor(N/r).
Using N and D, we can perform rational resampling where N/D is a rational number close to the input rate r where we have N filters and we cycle through them as a polyphase filterbank with a stride of D so that i+1 = (i + D) % N.
To get the arbitrary rate, we want to interpolate between two points. For each value out, we take an output from the current filter, i, and the next filter i+1 and then linearly interpolate between the two based on the real resampling rate we want.
The linear interpolation only provides us with an approximation to the real sampling rate specified. The error is a quantization error between the two filters we used as our interpolation points. To this end, the number of filters, N, used determines the quantization error; the larger N, the smaller the noise. You can design for a specified noise floor by setting the filter size (parameters filter_size). The size defaults to 32 filters, which is about as good as most implementations need.
The trick with designing this filter is in how to specify the taps of the prototype filter. Like the PFB interpolator, the taps are specified using the interpolated filter rate. In this case, that rate is the input sample rate multiplied by the number of filters in the filterbank, which is also the interpolation rate. All other values should be relative to this rate.
For example, for a 32-filter arbitrary resampler and using the GNU Radio's firdes utility to build the filter, we build a low-pass filter with a sampling rate of fs, a 3-dB bandwidth of BW and a transition bandwidth of TB. We can also specify the out-of-band attenuation to use, ATT, and the filter window function (a Blackman-harris window in this case). The first input is the gain of the filter, which we specify here as the interpolation rate (32).
<B><EM>self._taps = gr.firdes.low_pass_2(32, 32*fs, BW, TB, attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
The theory behind this block can be found in Chapter 7.5 of the following book.
f. harris, "Multirate Signal Processing for Communication Systems", Upper Saddle River, NJ: Prentice Hall, Inc. 2004.
gr_pfb_arb_resampler_fff::~gr_pfb_arb_resampler_fff | ( | ) |
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virtual |
compute output items from input items
noutput_items | number of output items to write on each output stream |
ninput_items | number of input items available on each input stream |
input_items | vector of pointers to the input items, one entry per input stream |
output_items | vector of pointers to the output items, one entry per output stream |
general_work must call consume or consume_each to indicate how many items were consumed on each input stream.
Reimplemented from gr_block.
void gr_pfb_arb_resampler_fff::print_taps | ( | ) |
Print all of the filterbank taps to screen.
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inline |
References gr_block::set_relative_rate().
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friend |
Build the polyphase filterbank arbitray resampler.
rate | (float) Specifies the resampling rate to use |
taps | (vector/list of floats) The prototype filter to populate the filterbank. The taps should be generated at the filter_size sampling rate. |
filter_size | (unsigned int) The number of filters in the filter bank. This is directly related to quantization noise introduced during the resampling. Defaults to 32 filters. |