PeerStreamer

/*

 * Real Audio 1.0 (14.4K) encoder

 * Copyright (c) 2010 Francesco Lavra <francescolavra@interfree.it>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * Real Audio 1.0 (14.4K) encoder

 * @author Francesco Lavra <francescolavra@interfree.it>

 */

#include <float.h>

#include "avcodec.h"

#include "put_bits.h"

#include "lpc.h"

#include "celp_filters.h"

#include "ra144.h"

static av_cold int ra144_encode_init(AVCodecContext * avctx)

{

    RA144Context *ractx;

    if (avctx->sample_fmt != SAMPLE_FMT_S16) {

        av_log(avctx, AV_LOG_ERROR, "invalid sample format\n");

        return -1;

    }

    if (avctx->channels != 1) {

        av_log(avctx, AV_LOG_ERROR, "invalid number of channels: %d\n",

               avctx->channels);

        return -1;

    }

    avctx->frame_size = NBLOCKS * BLOCKSIZE;

    avctx->bit_rate = 8000;

    ractx = avctx->priv_data;

    ractx->lpc_coef[0] = ractx->lpc_tables[0];

    ractx->lpc_coef[1] = ractx->lpc_tables[1];

    ractx->avctx = avctx;

    dsputil_init(&ractx->dsp, avctx);

    return 0;

}

/**

 * Quantize a value by searching a sorted table for the element with the

 * nearest value

 *

 * @param value value to quantize

 * @param table array containing the quantization table

 * @param size size of the quantization table

 * @return index of the quantization table corresponding to the element with the

 *         nearest value

 */

static int quantize(int value, const int16_t *table, unsigned int size)

{

    unsigned int low = 0, high = size - 1;

    while (1) {

        int index = (low + high) >> 1;

        int error = table[index] - value;

        if (index == low)

            return table[high] + error > value ? low : high;

        if (error > 0) {

            high = index;

        } else {

            low = index;

        }

    }

}

/**

 * Orthogonalize a vector to another vector

 *

 * @param v vector to orthogonalize

 * @param u vector against which orthogonalization is performed

 */

static void orthogonalize(float *v, const float *u)

{

    int i;

    float num = 0, den = 0;

    for (i = 0; i < BLOCKSIZE; i++) {

        num += v[i] * u[i];

        den += u[i] * u[i];

    }

    num /= den;

    for (i = 0; i < BLOCKSIZE; i++)

        v[i] -= num * u[i];

}

/**

 * Calculate match score and gain of an LPC-filtered vector with respect to

 * input data, possibly othogonalizing it to up to 2 other vectors

 *

 * @param work array used to calculate the filtered vector

 * @param coefs coefficients of the LPC filter

 * @param vect original vector

 * @param ortho1 first vector against which orthogonalization is performed

 * @param ortho2 second vector against which orthogonalization is performed

 * @param data input data

 * @param score pointer to variable where match score is returned

 * @param gain pointer to variable where gain is returned

 */

static void get_match_score(float *work, const float *coefs, float *vect,

                            const float *ortho1, const float *ortho2,

                            const float *data, float *score, float *gain)

{

    float c, g;

    int i;

    ff_celp_lp_synthesis_filterf(work, coefs, vect, BLOCKSIZE, LPC_ORDER);

    if (ortho1)

        orthogonalize(work, ortho1);

    if (ortho2)

        orthogonalize(work, ortho2);

    c = g = 0;

    for (i = 0; i < BLOCKSIZE; i++) {

        g += work[i] * work[i];

        c += data[i] * work[i];

    }

    if (c <= 0) {

        *score = 0;

        return;

    }

    *gain = c / g;

    *score = *gain * c;

}

/**

 * Create a vector from the adaptive codebook at a given lag value

 *

 * @param vect array where vector is stored

 * @param cb adaptive codebook

 * @param lag lag value

 */

static void create_adapt_vect(float *vect, const int16_t *cb, int lag)

{

    int i;

    cb += BUFFERSIZE - lag;

    for (i = 0; i < FFMIN(BLOCKSIZE, lag); i++)

        vect[i] = cb[i];

    if (lag < BLOCKSIZE)

        for (i = 0; i < BLOCKSIZE - lag; i++)

            vect[lag + i] = cb[i];

}

/**

 * Search the adaptive codebook for the best entry and gain and remove its

 * contribution from input data

 *

 * @param adapt_cb array from which the adaptive codebook is extracted

 * @param work array used to calculate LPC-filtered vectors

 * @param coefs coefficients of the LPC filter

 * @param data input data

 * @return index of the best entry of the adaptive codebook

 */

static int adaptive_cb_search(const int16_t *adapt_cb, float *work,

                              const float *coefs, float *data)

{

    int i, best_vect;

    float score, gain, best_score, best_gain;

    float exc[BLOCKSIZE];

    gain = best_score = 0;

    for (i = BLOCKSIZE / 2; i <= BUFFERSIZE; i++) {

        create_adapt_vect(exc, adapt_cb, i);

        get_match_score(work, coefs, exc, NULL, NULL, data, &score, &gain);

        if (score > best_score) {

            best_score = score;

            best_vect = i;

            best_gain = gain;

        }

    }

    if (!best_score)

        return 0;

    /**

     * Re-calculate the filtered vector from the vector with maximum match score

     * and remove its contribution from input data.

     */

    create_adapt_vect(exc, adapt_cb, best_vect);

    ff_celp_lp_synthesis_filterf(work, coefs, exc, BLOCKSIZE, LPC_ORDER);

    for (i = 0; i < BLOCKSIZE; i++)

        data[i] -= best_gain * work[i];

    return (best_vect - BLOCKSIZE / 2 + 1);

}

/**

 * Find the best vector of a fixed codebook by applying an LPC filter to

 * codebook entries, possibly othogonalizing them to up to 2 other vectors and

 * matching the results with input data

 *

 * @param work array used to calculate the filtered vectors

 * @param coefs coefficients of the LPC filter

 * @param cb fixed codebook

 * @param ortho1 first vector against which orthogonalization is performed

 * @param ortho2 second vector against which orthogonalization is performed

 * @param data input data

 * @param idx pointer to variable where the index of the best codebook entry is

 *        returned

 * @param gain pointer to variable where the gain of the best codebook entry is

 *        returned

 */

static void find_best_vect(float *work, const float *coefs,

                           const int8_t cb[][BLOCKSIZE], const float *ortho1,

                           const float *ortho2, float *data, int *idx,

                           float *gain)

{

    int i, j;

    float g, score, best_score;

    float vect[BLOCKSIZE];

    *idx = *gain = best_score = 0;

    for (i = 0; i < FIXED_CB_SIZE; i++) {

        for (j = 0; j < BLOCKSIZE; j++)

            vect[j] = cb[i][j];

        get_match_score(work, coefs, vect, ortho1, ortho2, data, &score, &g);

        if (score > best_score) {

            best_score = score;

            *idx = i;

            *gain = g;

        }

    }

}

/**

 * Search the two fixed codebooks for the best entry and gain

 *

 * @param work array used to calculate LPC-filtered vectors

 * @param coefs coefficients of the LPC filter

 * @param data input data

 * @param cba_idx index of the best entry of the adaptive codebook

 * @param cb1_idx pointer to variable where the index of the best entry of the

 *        first fixed codebook is returned

 * @param cb2_idx pointer to variable where the index of the best entry of the

 *        second fixed codebook is returned

 */

static void fixed_cb_search(float *work, const float *coefs, float *data,

                            int cba_idx, int *cb1_idx, int *cb2_idx)

{

    int i, ortho_cb1;

    float gain;

    float cba_vect[BLOCKSIZE], cb1_vect[BLOCKSIZE];

    float vect[BLOCKSIZE];

    /**

     * The filtered vector from the adaptive codebook can be retrieved from

     * work, because this function is called just after adaptive_cb_search().

     */

    if (cba_idx)

        memcpy(cba_vect, work, sizeof(cba_vect));

    find_best_vect(work, coefs, ff_cb1_vects, cba_idx ? cba_vect : NULL, NULL,

                   data, cb1_idx, &gain);

    /**

     * Re-calculate the filtered vector from the vector with maximum match score

     * and remove its contribution from input data.

     */

    if (gain) {

        for (i = 0; i < BLOCKSIZE; i++)

            vect[i] = ff_cb1_vects[*cb1_idx][i];

        ff_celp_lp_synthesis_filterf(work, coefs, vect, BLOCKSIZE, LPC_ORDER);

        if (cba_idx)

            orthogonalize(work, cba_vect);

        for (i = 0; i < BLOCKSIZE; i++)

            data[i] -= gain * work[i];

        memcpy(cb1_vect, work, sizeof(cb1_vect));

        ortho_cb1 = 1;

    } else

        ortho_cb1 = 0;

    find_best_vect(work, coefs, ff_cb2_vects, cba_idx ? cba_vect : NULL,

                   ortho_cb1 ? cb1_vect : NULL, data, cb2_idx, &gain);

}

/**

 * Encode a subblock of the current frame

 *

 * @param ractx encoder context

 * @param sblock_data input data of the subblock

 * @param lpc_coefs coefficients of the LPC filter

 * @param rms RMS of the reflection coefficients

 * @param pb pointer to PutBitContext of the current frame

 */

static void ra144_encode_subblock(RA144Context *ractx,

                                  const int16_t *sblock_data,

                                  const int16_t *lpc_coefs, unsigned int rms,

                                  PutBitContext *pb)

{

    float data[BLOCKSIZE], work[LPC_ORDER + BLOCKSIZE];

    float coefs[LPC_ORDER];

    float zero[BLOCKSIZE], cba[BLOCKSIZE], cb1[BLOCKSIZE], cb2[BLOCKSIZE];

    int16_t cba_vect[BLOCKSIZE];

    int cba_idx, cb1_idx, cb2_idx, gain;

    int i, n, m[3];

    float g[3];

    float error, best_error;

    for (i = 0; i < LPC_ORDER; i++) {

        work[i] = ractx->curr_sblock[BLOCKSIZE + i];

        coefs[i] = lpc_coefs[i] * (1/4096.0);

    }

    /**

     * Calculate the zero-input response of the LPC filter and subtract it from

     * input data.

     */

    memset(data, 0, sizeof(data));

    ff_celp_lp_synthesis_filterf(work + LPC_ORDER, coefs, data, BLOCKSIZE,

                                 LPC_ORDER);

    for (i = 0; i < BLOCKSIZE; i++) {

        zero[i] = work[LPC_ORDER + i];

        data[i] = sblock_data[i] - zero[i];

    }

    /**

     * Codebook search is performed without taking into account the contribution

     * of the previous subblock, since it has been just subtracted from input

     * data.

     */

    memset(work, 0, LPC_ORDER * sizeof(*work));

    cba_idx = adaptive_cb_search(ractx->adapt_cb, work + LPC_ORDER, coefs,

                                 data);

    if (cba_idx) {

        /**

         * The filtered vector from the adaptive codebook can be retrieved from

         * work, see implementation of adaptive_cb_search().

         */

        memcpy(cba, work + LPC_ORDER, sizeof(cba));

        ff_copy_and_dup(cba_vect, ractx->adapt_cb, cba_idx + BLOCKSIZE / 2 - 1);

        m[0] = (ff_irms(cba_vect) * rms) >> 12;

    }

    fixed_cb_search(work + LPC_ORDER, coefs, data, cba_idx, &cb1_idx, &cb2_idx);

    for (i = 0; i < BLOCKSIZE; i++) {

        cb1[i] = ff_cb1_vects[cb1_idx][i];

        cb2[i] = ff_cb2_vects[cb2_idx][i];

    }

    ff_celp_lp_synthesis_filterf(work + LPC_ORDER, coefs, cb1, BLOCKSIZE,

                                 LPC_ORDER);

    memcpy(cb1, work + LPC_ORDER, sizeof(cb1));

    m[1] = (ff_cb1_base[cb1_idx] * rms) >> 8;

    ff_celp_lp_synthesis_filterf(work + LPC_ORDER, coefs, cb2, BLOCKSIZE,

                                 LPC_ORDER);

    memcpy(cb2, work + LPC_ORDER, sizeof(cb2));

    m[2] = (ff_cb2_base[cb2_idx] * rms) >> 8;

    best_error = FLT_MAX;

    gain = 0;

    for (n = 0; n < 256; n++) {

        g[1] = ((ff_gain_val_tab[n][1] * m[1]) >> ff_gain_exp_tab[n]) *

               (1/4096.0);

        g[2] = ((ff_gain_val_tab[n][2] * m[2]) >> ff_gain_exp_tab[n]) *

               (1/4096.0);

        error = 0;

        if (cba_idx) {

            g[0] = ((ff_gain_val_tab[n][0] * m[0]) >> ff_gain_exp_tab[n]) *

                   (1/4096.0);

            for (i = 0; i < BLOCKSIZE; i++) {

                data[i] = zero[i] + g[0] * cba[i] + g[1] * cb1[i] +

                          g[2] * cb2[i];

                error += (data[i] - sblock_data[i]) *

                         (data[i] - sblock_data[i]);

            }

        } else {

            for (i = 0; i < BLOCKSIZE; i++) {

                data[i] = zero[i] + g[1] * cb1[i] + g[2] * cb2[i];

                error += (data[i] - sblock_data[i]) *

                         (data[i] - sblock_data[i]);

            }

        }

        if (error < best_error) {

            best_error = error;

            gain = n;

        }

    }

    put_bits(pb, 7, cba_idx);

    put_bits(pb, 8, gain);

    put_bits(pb, 7, cb1_idx);

    put_bits(pb, 7, cb2_idx);

    ff_subblock_synthesis(ractx, lpc_coefs, cba_idx, cb1_idx, cb2_idx, rms,

                          gain);

}

static int ra144_encode_frame(AVCodecContext *avctx, uint8_t *frame,

                              int buf_size, void *data)

{

    static const uint8_t sizes[LPC_ORDER] = {64, 32, 32, 16, 16, 8, 8, 8, 8, 4};

    static const uint8_t bit_sizes[LPC_ORDER] = {6, 5, 5, 4, 4, 3, 3, 3, 3, 2};

    RA144Context *ractx;

    PutBitContext pb;

    int32_t lpc_data[NBLOCKS * BLOCKSIZE];

    int32_t lpc_coefs[LPC_ORDER][MAX_LPC_ORDER];

    int shift[LPC_ORDER];

    int16_t block_coefs[NBLOCKS][LPC_ORDER];

    int lpc_refl[LPC_ORDER];    /**< reflection coefficients of the frame */

    unsigned int refl_rms[NBLOCKS]; /**< RMS of the reflection coefficients */

    int energy = 0;

    int i, idx;

    if (buf_size < FRAMESIZE) {

        av_log(avctx, AV_LOG_ERROR, "output buffer too small\n");

        return 0;

    }

    ractx = avctx->priv_data;

    /**

     * Since the LPC coefficients are calculated on a frame centered over the

     * fourth subframe, to encode a given frame, data from the next frame is

     * needed. In each call to this function, the previous frame (whose data are

     * saved in the encoder context) is encoded, and data from the current frame

     * are saved in the encoder context to be used in the next function call.

     */

    for (i = 0; i < (2 * BLOCKSIZE + BLOCKSIZE / 2); i++) {

        lpc_data[i] = ractx->curr_block[BLOCKSIZE + BLOCKSIZE / 2 + i];

        energy += (lpc_data[i] * lpc_data[i]) >> 4;

    }

    for (i = 2 * BLOCKSIZE + BLOCKSIZE / 2; i < NBLOCKS * BLOCKSIZE; i++) {

        lpc_data[i] = *((int16_t *)data + i - 2 * BLOCKSIZE - BLOCKSIZE / 2) >>

                      2;

        energy += (lpc_data[i] * lpc_data[i]) >> 4;

    }

    energy = ff_energy_tab[quantize(ff_t_sqrt(energy >> 5) >> 10, ff_energy_tab,

                                    32)];

    ff_lpc_calc_coefs(&ractx->dsp, lpc_data, NBLOCKS * BLOCKSIZE, LPC_ORDER,

                      LPC_ORDER, 16, lpc_coefs, shift, AV_LPC_TYPE_LEVINSON,

                      0, ORDER_METHOD_EST, 12, 0);

    for (i = 0; i < LPC_ORDER; i++)

        block_coefs[NBLOCKS - 1][i] = -(lpc_coefs[LPC_ORDER - 1][i] <<

                                        (12 - shift[LPC_ORDER - 1]));

    /**

     * TODO: apply perceptual weighting of the input speech through bandwidth

     * expansion of the LPC filter.

     */

    if (ff_eval_refl(lpc_refl, block_coefs[NBLOCKS - 1], avctx)) {

        /**

         * The filter is unstable: use the coefficients of the previous frame.

         */

        ff_int_to_int16(block_coefs[NBLOCKS - 1], ractx->lpc_coef[1]);

        ff_eval_refl(lpc_refl, block_coefs[NBLOCKS - 1], avctx);

    }

    init_put_bits(&pb, frame, buf_size);

    for (i = 0; i < LPC_ORDER; i++) {

        idx = quantize(lpc_refl[i], ff_lpc_refl_cb[i], sizes[i]);

        put_bits(&pb, bit_sizes[i], idx);

        lpc_refl[i] = ff_lpc_refl_cb[i][idx];

    }

    ractx->lpc_refl_rms[0] = ff_rms(lpc_refl);

    ff_eval_coefs(ractx->lpc_coef[0], lpc_refl);

    refl_rms[0] = ff_interp(ractx, block_coefs[0], 1, 1, ractx->old_energy);

    refl_rms[1] = ff_interp(ractx, block_coefs[1], 2,

                            energy <= ractx->old_energy,

                            ff_t_sqrt(energy * ractx->old_energy) >> 12);

    refl_rms[2] = ff_interp(ractx, block_coefs[2], 3, 0, energy);

    refl_rms[3] = ff_rescale_rms(ractx->lpc_refl_rms[0], energy);

    ff_int_to_int16(block_coefs[NBLOCKS - 1], ractx->lpc_coef[0]);

    put_bits(&pb, 5, quantize(energy, ff_energy_tab, 32));

    for (i = 0; i < NBLOCKS; i++)

        ra144_encode_subblock(ractx, ractx->curr_block + i * BLOCKSIZE,

                              block_coefs[i], refl_rms[i], &pb);

    flush_put_bits(&pb);

    ractx->old_energy = energy;

    ractx->lpc_refl_rms[1] = ractx->lpc_refl_rms[0];

    FFSWAP(unsigned int *, ractx->lpc_coef[0], ractx->lpc_coef[1]);

    for (i = 0; i < NBLOCKS * BLOCKSIZE; i++)

        ractx->curr_block[i] = *((int16_t *)data + i) >> 2;

    return FRAMESIZE;

}

AVCodec ra_144_encoder =

{

    "real_144",

    AVMEDIA_TYPE_AUDIO,

    CODEC_ID_RA_144,

    sizeof(RA144Context),

    ra144_encode_init,

    ra144_encode_frame,

    .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K) encoder"),

};