[Speex-dev] 11kbps narrowband on a 24bit DSP

[Barr, Russell]

Hi,

 

I am using speex 1.2beta2 on a 24bit DSP that has a severe program and
data space limitations. I am only interested in the speex decoder for
11kbps narrowband implementation. 

 

I am using the following parameters and structures

 

160,    /*frameSize*/

  40,     /*subframeSize*/

  10,     /*lpcSize*/

  17,     /*pitchStart*/

  144,    /*pitchEnd*/ 

 

/* 11 kbps medium bit-rate mode */

static const SpeexSubmode nb_submode4 = {

   -1,

   0,

   1,

   0,

   /*LSP quantization*/

   lsp_quant_lbr,

   lsp_unquant_lbr,

   /*Pitch quantization*/

   pitch_search_3tap,

   pitch_unquant_3tap,

   &ltp_params_med,

   /*Innovation quantization*/

   split_cb_search_shape_sign,

   split_cb_shape_sign_unquant,

   &split_cb_nb_med,

   QCONST16(.45,15),

   220

};

 

/* Parameters for Long-Term Prediction (LTP)*/

static const ltp_params ltp_params_lbr = {

   gain_cdbk_lbr,

   5,

   7

};

 

/* Split-VQ innovation parameters narrowband */

static const split_cb_params split_cb_nb_med = {

   8,               /*subvect_size*/

   5,               /*nb_subvect*/

   exc_8_128_table, /*shape_cb*/

   7,               /*shape_bits*/

   0,

 

 

 

I have three problems.

 

1.	My DSP has 24 bits register and memory with a 24 X 24 = 48 bit
multiply and a 56 bit accumulator. I see scaling shifts when using 32
bit registers. Can anyone tell me what scaling values like 

 

#define LPC_SCALING  8192

#define SIG_SCALING  16384

#define LSP_SCALING  8192.

#define GAMMA_SCALING 32768.

#define GAIN_SCALING 64

#define GAIN_SCALING_1 0.015625

 

#define LPC_SHIFT    13

#define LSP_SHIFT    13

#define SIG_SHIFT    14

 

            Would be required for a 24 bit register?  

 

2.	I would like to only include only the data tables as required to
support 11kbps narrowband mode. I think they would be the following
signed byte tables

cdbk_nb[640]

cdbk_nb_low1[320]

cdbk_nb_high1[320]

gain_cdbk_lbr[128]

exc_8_128_table[1024]

            Have I missed any?

 

3.	I would like to estimate the code space and duty cycle
requirements using fix point 11kbps narrowband decode. I think I have
identified most of the routines that use most of the duty cycle but I am
not sure if I have found them all. 

speex_bits_unpack_unsigned()

peex_bits_unpack_signed()

split_cb_shape_sign_unquant()

pitch_unquant_3tap()

lsp_unquant_lbr()

            I will be porting there routines to assembly and would like
to know that I have a chance of fitting them in the 2K I have free.  

            Is there a minimal list of decode routines that are
required?

 

 

Thanks for any help possible

 

Russell Barr

Vocollect, Inc

703 Rodi Road

Pittsburgh, Pa 15235

 

Phone: 412-349-2581

Fax:     412-829-0972

Email:  rbarr at vocollect.com <mailto:rbarr at vocollect.com> 

 

www.vocollect.com <http://www.vocollect.com>  

 

Vocollect Voice-Directed Work

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