I've never tried Speex on a 24-bit DSP, but I would suggest actually
leaving the code (nearly) as-is. The scaling factors actually should not
change because I'm using integer multiplications, not fractional
multiplications. So what should happen is that the top 8 bits or 24-bit
values and the top 16-bit of 48-bit values will be unused (filled with
sign bits). There may be a few cases where 32-bit values could be
changed to 24-bit ones, but don't bother with that in the short term.
Jean-Marc
Barr, Russell a ?crit :> 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,
>
> <p_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@vocollect.com <mailto:rbarr@vocollect.com>
>
>
>
> www.vocollect.com <http://www.vocollect.com>
>
>
>
> Vocollect Voice-Directed Work
>
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