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gr::vocoder::cvsd_encode_sb Class Referenceabstract

This block performs CVSD audio encoding. Its design and implementation is modeled after the CVSD encoder/decoder specifications defined in the Bluetooth standard. More...

#include <gnuradio/vocoder/cvsd_encode_sb.h>

Public Types

typedef boost::shared_ptr
< cvsd_encode_sb
sptr
 
- Public Types inherited from gr::block
enum  { WORK_CALLED_PRODUCE = -2, WORK_DONE = -1 }
 Magic return values from general_work. More...
 
enum  tag_propagation_policy_t { TPP_DONT = 0, TPP_ALL_TO_ALL = 1, TPP_ONE_TO_ONE = 2 }
 

Public Member Functions

virtual short min_step ()=0
 
virtual short max_step ()=0
 
virtual double step_decay ()=0
 
virtual double accum_decay ()=0
 
virtual int K ()=0
 
virtual int J ()=0
 
virtual short pos_accum_max ()=0
 
virtual short neg_accum_max ()=0
 
- Public Member Functions inherited from gr::sync_decimator
unsigned decimation () const
 
void set_decimation (unsigned decimation)
 
void forecast (int noutput_items, gr_vector_int &ninput_items_required)
 Estimate input requirements given output request. More...
 
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...
 
int fixed_rate_ninput_to_noutput (int ninput)
 Given ninput samples, return number of output samples that will be produced. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
 
int fixed_rate_noutput_to_ninput (int noutput)
 Given noutput samples, return number of input samples required to produce noutput. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
 
- Public Member Functions inherited from gr::sync_block
virtual int work (int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)=0
 just like gr::block::general_work, only this arranges to call consume_each for you More...
 
- Public Member Functions inherited from gr::block
virtual ~block ()
 
unsigned history () const
 
void set_history (unsigned history)
 
void declare_sample_delay (int which, unsigned delay)
 
void declare_sample_delay (unsigned delay)
 
unsigned sample_delay (int which) const
 
bool fixed_rate () const
 Return true if this block has a fixed input to output rate. More...
 
virtual bool start ()
 Called to enable drivers, etc for i/o devices. More...
 
virtual bool stop ()
 Called to disable drivers, etc for i/o devices. More...
 
void set_output_multiple (int multiple)
 Constrain the noutput_items argument passed to forecast and general_work. More...
 
int output_multiple () const
 
bool output_multiple_set () const
 
void set_alignment (int multiple)
 Constrains buffers to work on a set item alignment (for SIMD) More...
 
int alignment () const
 
void set_unaligned (int na)
 
int unaligned () const
 
void set_is_unaligned (bool u)
 
bool is_unaligned () const
 
void consume (int which_input, int how_many_items)
 Tell the scheduler how_many_items of input stream which_input were consumed. This function should be called at the end of work() or general_work(), after all processing is finished. More...
 
void consume_each (int how_many_items)
 Tell the scheduler how_many_items were consumed on each input stream. More...
 
void produce (int which_output, int how_many_items)
 Tell the scheduler how_many_items were produced on output stream which_output. More...
 
void set_relative_rate (double relative_rate)
 Set the approximate output rate / input rate. More...
 
double relative_rate () const
 return the approximate output rate / input rate More...
 
uint64_t nitems_read (unsigned int which_input)
 Return the number of items read on input stream which_input. More...
 
uint64_t nitems_written (unsigned int which_output)
 Return the number of items written on output stream which_output. More...
 
tag_propagation_policy_t tag_propagation_policy ()
 Asks for the policy used by the scheduler to moved tags downstream. More...
 
void set_tag_propagation_policy (tag_propagation_policy_t p)
 Set the policy by the scheduler to determine how tags are moved downstream. More...
 
int min_noutput_items () const
 Return the minimum number of output items this block can produce during a call to work. More...
 
void set_min_noutput_items (int m)
 Set the minimum number of output items this block can produce during a call to work. More...
 
int max_noutput_items ()
 Return the maximum number of output items this block will handle during a call to work. More...
 
void set_max_noutput_items (int m)
 Set the maximum number of output items this block will handle during a call to work. More...
 
void unset_max_noutput_items ()
 Clear the switch for using the max_noutput_items value of this block. More...
 
bool is_set_max_noutput_items ()
 Ask the block if the flag is or is not set to use the internal value of max_noutput_items during a call to work. More...
 
void expand_minmax_buffer (int port)
 
long max_output_buffer (size_t i)
 Returns max buffer size on output port i. More...
 
void set_max_output_buffer (long max_output_buffer)
 Request limit on max buffer size on all output ports. More...
 
void set_max_output_buffer (int port, long max_output_buffer)
 Request limit on max buffer size on output port port. More...
 
long min_output_buffer (size_t i)
 Returns min buffer size on output port i. More...
 
void set_min_output_buffer (long min_output_buffer)
 Request limit on the mininum buffer size on all output ports. More...
 
void set_min_output_buffer (int port, long min_output_buffer)
 Request limit on min buffer size on output port port. More...
 
float pc_noutput_items ()
 Gets instantaneous noutput_items performance counter. More...
 
float pc_noutput_items_avg ()
 Gets average noutput_items performance counter. More...
 
float pc_noutput_items_var ()
 Gets variance of noutput_items performance counter. More...
 
float pc_nproduced ()
 Gets instantaneous num items produced performance counter. More...
 
float pc_nproduced_avg ()
 Gets average num items produced performance counter. More...
 
float pc_nproduced_var ()
 Gets variance of num items produced performance counter. More...
 
float pc_input_buffers_full (int which)
 Gets instantaneous fullness of which input buffer. More...
 
float pc_input_buffers_full_avg (int which)
 Gets average fullness of which input buffer. More...
 
float pc_input_buffers_full_var (int which)
 Gets variance of fullness of which input buffer. More...
 
std::vector< float > pc_input_buffers_full ()
 Gets instantaneous fullness of all input buffers. More...
 
std::vector< float > pc_input_buffers_full_avg ()
 Gets average fullness of all input buffers. More...
 
std::vector< float > pc_input_buffers_full_var ()
 Gets variance of fullness of all input buffers. More...
 
float pc_output_buffers_full (int which)
 Gets instantaneous fullness of which input buffer. More...
 
float pc_output_buffers_full_avg (int which)
 Gets average fullness of which input buffer. More...
 
float pc_output_buffers_full_var (int which)
 Gets variance of fullness of which input buffer. More...
 
std::vector< float > pc_output_buffers_full ()
 Gets instantaneous fullness of all output buffers. More...
 
std::vector< float > pc_output_buffers_full_avg ()
 Gets average fullness of all output buffers. More...
 
std::vector< float > pc_output_buffers_full_var ()
 Gets variance of fullness of all output buffers. More...
 
float pc_work_time ()
 Gets instantaneous clock cycles spent in work. More...
 
float pc_work_time_avg ()
 Gets average clock cycles spent in work. More...
 
float pc_work_time_var ()
 Gets average clock cycles spent in work. More...
 
float pc_work_time_total ()
 Gets total clock cycles spent in work. More...
 
float pc_throughput_avg ()
 Gets average throughput. More...
 
void reset_perf_counters ()
 Resets the performance counters. More...
 
void setup_pc_rpc ()
 Sets up export of perf. counters to ControlPort. Only called by the scheduler. More...
 
bool is_pc_rpc_set ()
 Checks if this block is already exporting perf. counters to ControlPort. More...
 
void no_pc_rpc ()
 If the block calls this in its constructor, it's perf. counters will not be exported. More...
 
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...
 
int active_thread_priority ()
 Get the current thread priority in use. More...
 
int thread_priority ()
 Get the current thread priority stored. More...
 
int set_thread_priority (int priority)
 Set the current thread priority. More...
 
bool update_rate () const
 
void system_handler (pmt::pmt_t msg)
 the system message handler More...
 
bool finished ()
 returns true when execution has completed due to a message connection More...
 
block_detail_sptr detail () const
 
void set_detail (block_detail_sptr detail)
 
void notify_msg_neighbors ()
 Tell msg neighbors we are finished. More...
 
void clear_finished ()
 Make sure we dont think we are finished. More...
 
- Public Member Functions inherited from gr::basic_block
pmt::pmt_t message_subscribers (pmt::pmt_t port)
 
virtual ~basic_block ()
 
long unique_id () const
 
long symbolic_id () const
 
std::string name () const
 
std::string symbol_name () const
 
gr::io_signature::sptr input_signature () const
 
gr::io_signature::sptr output_signature () const
 
basic_block_sptr to_basic_block ()
 
bool alias_set ()
 
std::string alias ()
 
pmt::pmt_t alias_pmt ()
 
void set_block_alias (std::string name)
 
void message_port_register_in (pmt::pmt_t port_id)
 
void message_port_register_out (pmt::pmt_t port_id)
 
void message_port_pub (pmt::pmt_t port_id, pmt::pmt_t msg)
 
void message_port_sub (pmt::pmt_t port_id, pmt::pmt_t target)
 
void message_port_unsub (pmt::pmt_t port_id, pmt::pmt_t target)
 
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...
 
void _post (pmt::pmt_t which_port, pmt::pmt_t msg)
 
bool empty_p (pmt::pmt_t which_port)
 is the queue empty? More...
 
bool empty_p ()
 
bool empty_handled_p (pmt::pmt_t which_port)
 are all msg ports with handlers empty? More...
 
bool empty_handled_p ()
 
size_t nmsgs (pmt::pmt_t which_port)
 How many messages in the queue? More...
 
void insert_tail (pmt::pmt_t which_port, pmt::pmt_t msg)
 
pmt::pmt_t delete_head_nowait (pmt::pmt_t which_port)
 
pmt::pmt_t delete_head_blocking (pmt::pmt_t which_port, unsigned int millisec=0)
 
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)
 
const msg_queue_map_t & get_msg_map (void) const
 
virtual void setup_rpc ()
 Set up the RPC registered variables. More...
 
bool is_rpc_set ()
 Ask if this block has been registered to the RPC. More...
 
void rpc_set ()
 When the block is registered with the RPC, set this. More...
 
virtual bool check_topology (int ninputs, int noutputs)
 Confirm that ninputs and noutputs is an acceptable combination. More...
 
template<typename T >
void set_msg_handler (pmt::pmt_t which_port, T msg_handler)
 Set the callback that is fired when messages are available. More...
 
- Public Member Functions inherited from gr::msg_accepter
 msg_accepter ()
 
 ~msg_accepter ()
 
void post (pmt::pmt_t which_port, pmt::pmt_t msg)
 send msg to msg_accepter on port which_port More...
 
- Public Member Functions inherited from gr::messages::msg_accepter
 msg_accepter ()
 

Static Public Member Functions

static sptr make (short min_step=10, short max_step=1280, double step_decay=0.9990234375, double accum_decay=0.96875, int K=32, int J=4, short pos_accum_max=32767, short neg_accum_max=-32767)
 Constructor parameters to initialize the CVSD encoder. The default values are modeled after the Bluetooth standard and should not be changed except by an advanced user. More...
 

Additional Inherited Members

- Protected Types inherited from gr::basic_block
enum  vcolor { WHITE, GREY, BLACK }
 
- Protected Member Functions inherited from gr::sync_decimator
 sync_decimator (void)
 
 sync_decimator (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature, unsigned decimation)
 
- Protected Member Functions inherited from gr::sync_block
 sync_block (void)
 
 sync_block (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)
 
- Protected Member Functions inherited from gr::block
 block (void)
 
 block (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)
 
void set_fixed_rate (bool fixed_rate)
 
void add_item_tag (unsigned int which_output, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 Adds a new tag onto the given output buffer. More...
 
void add_item_tag (unsigned int which_output, const tag_t &tag)
 Adds a new tag onto the given output buffer. More...
 
void remove_item_tag (unsigned int which_input, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 DEPRECATED. Will be removed in 3.8. More...
 
void remove_item_tag (unsigned int which_input, const tag_t &tag)
 DEPRECATED. Will be removed in 3.8. More...
 
void get_tags_in_range (std::vector< tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end)
 Given a [start,end), returns a vector of all tags in the range. More...
 
void get_tags_in_range (std::vector< tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end, const pmt::pmt_t &key)
 Given a [start,end), returns a vector of all tags in the range with a given key. More...
 
void get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end)
 Gets all tags within the relative window of the current call to work. More...
 
void get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end, const pmt::pmt_t &key)
 Operates like gr::block::get_tags_in_window with the ability to only return tags with the specified key. More...
 
void enable_update_rate (bool en)
 
- Protected Member Functions inherited from gr::basic_block
 basic_block (void)
 
 basic_block (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)
 Protected constructor prevents instantiation by non-derived classes. More...
 
void set_input_signature (gr::io_signature::sptr iosig)
 may only be called during constructor More...
 
void set_output_signature (gr::io_signature::sptr iosig)
 may only be called during constructor More...
 
void set_color (vcolor color)
 Allow the flowgraph to set for sorting and partitioning. More...
 
vcolor color () const
 
virtual 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)
 
- Protected Attributes inherited from gr::block
std::vector< long > d_max_output_buffer
 
std::vector< long > d_min_output_buffer
 
gr::thread::mutex d_setlock
 
gr::logger_ptr d_logger
 
gr::logger_ptr d_debug_logger
 
- Protected Attributes inherited from gr::basic_block
std::string d_name
 
gr::io_signature::sptr d_input_signature
 
gr::io_signature::sptr d_output_signature
 
long d_unique_id
 
long d_symbolic_id
 
std::string d_symbol_name
 
std::string d_symbol_alias
 
vcolor d_color
 
bool d_rpc_set
 
msg_queue_map_t msg_queue
 
std::vector< boost::any > d_rpc_vars
 
pmt::pmt_t d_message_subscribers
 

Detailed Description

This block performs CVSD audio encoding. Its design and implementation is modeled after the CVSD encoder/decoder specifications defined in the Bluetooth standard.

CVSD is a method for encoding speech that seeks to reduce the bandwidth required for digital voice transmission. CVSD takes advantage of strong correlation between samples, quantizing the difference in amplitude between two consecutive samples. This difference requires fewer quantization levels as compared to other methods that quantize the actual amplitude level, reducing the bandwidth. CVSD employs a two level quantizer (one bit) and an adaptive algorithm that allows for continuous step size adjustment.

The coder can represent low amplitude signals with accuracy without sacrificing performance on large amplitude signals, a trade off that occurs in some non-adaptive modulations.

The CVSD encoder effectively provides 8-to-1 compression. More specifically, each incoming audio sample is compared to an internal reference value. If the input is greater or equal to the reference, the encoder outputs a "1" bit. If the input is less than the reference, the encoder outputs a "0" bit. The reference value is then updated accordingly based on the frequency of outputted "1" or "0" bits. By grouping 8 outputs bits together, the encoder essentially produce one output byte for every 8 input audio samples.

This encoder requires that input audio samples are 2-byte short signed integers. The result bandwidth conversion, therefore, is 16 input bytes of raw audio data to 1 output byte of encoded audio data.

The CVSD encoder module must be prefixed by an up-converter to over-sample the audio data prior to encoding. The Bluetooth standard specifically calls for a 1-to-8 interpolating up-converter. While this reduces the overall compression of the codec, this is required so that the encoder can accurately compute the slope between adjacent audio samples and correctly update its internal reference value.

References:

  1. Continuously Variable Slope Delta Modulation (CVSD) A Tutorial, Available: http://www.eetkorea.com/ARTICLES/2003AUG/A/2003AUG29_NTEK_RFD_AN02.PDF.
  2. Specification of The Bluetooth System Available: http://grouper.ieee.org/groups/802/15/Bluetooth/core_10_b.pdf.
  3. McGarrity, S., Bluetooth Full Duplex Voice and Data Transmission. 2002. Bluetooth Voice Simulink Model, Available: http://www.mathworks.com/company/newsletters/digest/nov01/bluetooth.html

Member Typedef Documentation

Member Function Documentation

virtual double gr::vocoder::cvsd_encode_sb::accum_decay ( )
pure virtual
virtual int gr::vocoder::cvsd_encode_sb::J ( )
pure virtual
virtual int gr::vocoder::cvsd_encode_sb::K ( )
pure virtual
static sptr gr::vocoder::cvsd_encode_sb::make ( short  min_step = 10,
short  max_step = 1280,
double  step_decay = 0.9990234375,
double  accum_decay = 0.96875,
int  K = 32,
int  J = 4,
short  pos_accum_max = 32767,
short  neg_accum_max = -32767 
)
static

Constructor parameters to initialize the CVSD encoder. The default values are modeled after the Bluetooth standard and should not be changed except by an advanced user.

Parameters
min_stepMinimum step size used to update the internal reference. Default: "10"
max_stepMaximum step size used to update the internal reference. Default: "1280"
step_decayDecay factor applied to step size when there is not a run of J output 1s or 0s. Default: "0.9990234375" (i.e. 1-1/1024)
accum_decayDecay factor applied to the internal reference during every interation of the codec. Default: "0.96875" (i.e. 1-1/32)
KSize of shift register; the number of output bits remembered by codec (must be <= to 32). Default: "32"
JNumber of bits in the shift register that are equal; i.e. the size of a run of 1s, 0s. Default: "4"
pos_accum_maxMaximum integer value allowed for the internal reference. Default: "32767" (2^15 - 1 or MAXSHORT)
neg_accum_maxMinimum integer value allowed for the internal reference. Default: "-32767" (-2^15 + 1 or MINSHORT+1)
virtual short gr::vocoder::cvsd_encode_sb::max_step ( )
pure virtual
virtual short gr::vocoder::cvsd_encode_sb::min_step ( )
pure virtual
virtual short gr::vocoder::cvsd_encode_sb::neg_accum_max ( )
pure virtual
virtual short gr::vocoder::cvsd_encode_sb::pos_accum_max ( )
pure virtual
virtual double gr::vocoder::cvsd_encode_sb::step_decay ( )
pure virtual

The documentation for this class was generated from the following file: