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Adaptive gain control
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@ -145,6 +145,7 @@ typedef struct {
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int16_t onset; ///< detected onset level (0-2)
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int16_t was_periodic; ///< whether previous frame was declared as periodic or not (4.4)
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int16_t ht_prev_data; ///< previous data for 4.2.3, equation 86
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int gain_coeff; ///< (1.14) gain coefficient (4.2.4)
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uint16_t rand_value; ///< random number generator value (4.4.4)
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int ma_predictor_prev; ///< switched MA predictor of LSP quantizer from last good frame
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@ -348,6 +349,8 @@ static av_cold int decoder_init(AVCodecContext * avctx)
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/* Both 8kbit/s and 6.4kbit/s modes uses two subframes per frame. */
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avctx->frame_size = SUBFRAME_SIZE << 1;
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ctx->gain_coeff = 16384; // 1.0 in (1.14)
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for (k = 0; k < MA_NP + 1; k++) {
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ctx->past_quantizer_outputs[k] = ctx->past_quantizer_output_buf[k];
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for (i = 1; i < 11; i++)
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@ -397,6 +400,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
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int16_t fc[SUBFRAME_SIZE]; // fixed-codebook vector
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int16_t synth[SUBFRAME_SIZE+10]; // fixed-codebook vector
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int j;
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int gain_before, gain_after;
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int is_periodic = 0; // whether one of the subframes is declared as periodic or not
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if (*data_size < SUBFRAME_SIZE << 2) {
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@ -637,6 +641,11 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
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/* Save data (without postfilter) for use in next subframe. */
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memcpy(ctx->syn_filter_data, synth+SUBFRAME_SIZE, 10 * sizeof(int16_t));
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/* Calculate gain of unfiltered signal for use in AGC. */
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gain_before = 0;
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for (j = 0; j < SUBFRAME_SIZE; j++)
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gain_before += FFABS(synth[j+10]);
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/* Call postfilter and also update voicing decision for use in next frame. */
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g729_postfilter(
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&ctx->dsp,
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@ -650,6 +659,18 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
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synth+10,
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SUBFRAME_SIZE);
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/* Calculate gain of filtered signal for use in AGC. */
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gain_after = 0;
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for(j=0; j<SUBFRAME_SIZE; j++)
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gain_after += FFABS(synth[j+10]);
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ctx->gain_coeff = g729_adaptive_gain_control(
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gain_before,
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gain_after,
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synth+10,
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SUBFRAME_SIZE,
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ctx->gain_coeff);
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if (frame_erasure)
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ctx->pitch_delay_int_prev = FFMIN(ctx->pitch_delay_int_prev + 1, PITCH_DELAY_MAX);
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else
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@ -560,3 +560,51 @@ void g729_postfilter(DSPContext *dsp, int16_t* ht_prev_data, int16_t* voicing,
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*ht_prev_data = apply_tilt_comp(speech, pos_filter_data + 10, tilt_comp_coeff,
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subframe_size, *ht_prev_data);
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}
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/**
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* \brief Adaptive gain control (4.2.4)
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* \param gain_before gain of speech before applying postfilters
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* \param gain_after gain of speech after applying postfilters
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* \param speech [in/out] signal buffer
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* \param subframe_size length of subframe
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* \param gain_prev (3.12) previous value of gain coefficient
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*
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* \return (3.12) last value of gain coefficient
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*/
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int16_t g729_adaptive_gain_control(int gain_before, int gain_after, int16_t *speech,
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int subframe_size, int16_t gain_prev)
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{
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int gain; // (3.12)
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int n;
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int exp_before, exp_after;
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if(!gain_after && gain_before)
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return 0;
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if (gain_before) {
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exp_before = 14 - av_log2(gain_before);
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gain_before = bidir_sal(gain_before, exp_before);
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exp_after = 14 - av_log2(gain_after);
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gain_after = bidir_sal(gain_after, exp_after);
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if (gain_before < gain_after) {
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gain = (gain_before << 15) / gain_after;
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gain = bidir_sal(gain, exp_after - exp_before - 1);
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} else {
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gain = ((gain_before - gain_after) << 14) / gain_after + 0x4000;
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gain = bidir_sal(gain, exp_after - exp_before);
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}
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gain = (gain * G729_AGC_FAC1 + 0x4000) >> 15; // gain * (1-0.9875)
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} else
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gain = 0;
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for (n = 0; n < subframe_size; n++) {
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// gain_prev = gain + 0.9875 * gain_prev
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gain_prev = (G729_AGC_FACTOR * gain_prev + 0x4000) >> 15;
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gain_prev = av_clip_int16(gain + gain_prev);
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speech[n] = av_clip_int16((speech[n] * gain_prev + 0x2000) >> 14);
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}
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return gain_prev;
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}
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@ -39,6 +39,13 @@
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#define FORMANT_PP_FACTOR_NUM 18022 //0.55 in Q15
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#define FORMANT_PP_FACTOR_DEN 22938 //0.70 in Q15
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/**
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* gain adjustment factor (G.729, 4.2.4)
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* 0.9875 in Q15
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*/
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#define G729_AGC_FACTOR 32358
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#define G729_AGC_FAC1 (32768-G729_AGC_FACTOR)
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/**
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* 1.0 / (1.0 + 0.5) in Q15
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* where 0.5 is the minimum value of
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@ -92,4 +99,17 @@ void g729_postfilter(DSPContext *dsp, int16_t* ht_prev_data, int16_t* voicing,
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int16_t* pos_filter_data, int16_t *speech,
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int subframe_size);
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/**
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* \brief Adaptive gain control (4.2.4)
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* \param gain_before (Q0) gain of speech before applying postfilters
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* \param gain_after (Q0) gain of speech after applying postfilters
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* \param speech [in/out] (Q0) signal buffer
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* \param subframe_size length of subframe
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* \param gain_prev (Q12) previous value of gain coefficient
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*
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* \return (Q12) last value of gain coefficient
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*/
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int16_t g729_adaptive_gain_control(int gain_before, int gain_after, int16_t *speech,
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int subframe_size, int16_t gain_prev);
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#endif // FFMPEG_G729POSTFILTER_H
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