FFmpeg4/libavcodec/vorbis.c

/**
 * @file
 * Common code for Vorbis I encoder and decoder
 * @author Denes Balatoni  ( dbalatoni programozo hu )
 *
 * 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
 * Common code for Vorbis I encoder and decoder
 * @author Denes Balatoni  ( dbalatoni programozo hu )
 */

#include "libavutil/common.h"

#include "avcodec.h"
#include "vorbis.h"


/* Helper functions */

// x^(1/n)
unsigned int ff_vorbis_nth_root(unsigned int x, unsigned int n)
{
    unsigned int ret = 0, i, j;

    do {
        ++ret;
        for (i = 0, j = ret; i < n - 1; i++)
            j *= ret;
    } while (j <= x);

    return ret - 1;
}

// Generate vlc codes from vorbis huffman code lengths

// the two bits[p] > 32 checks should be redundant, all calling code should
// already ensure that, but since it allows overwriting the stack it seems
// reasonable to check redundantly.
int ff_vorbis_len2vlc(uint8_t *bits, uint32_t *codes, unsigned num)
{
    uint32_t exit_at_level[33] = { 404 };
    unsigned i, j, p, code;

    for (p = 0; (p < num) && (bits[p] == 0); ++p)
        ;
    if (p == num)
        return 0;

    codes[p] = 0;
    if (bits[p] > 32)
        return AVERROR_INVALIDDATA;
    for (i = 0; i < bits[p]; ++i)
        exit_at_level[i+1] = 1u << i;

    ++p;

    for (i = p; (i < num) && (bits[i] == 0); ++i)
        ;
    if (i == num)
        return 0;

    for (; p < num; ++p) {
        if (bits[p] > 32)
             return AVERROR_INVALIDDATA;
        if (bits[p] == 0)
             continue;
        // find corresponding exit(node which the tree can grow further from)
        for (i = bits[p]; i > 0; --i)
            if (exit_at_level[i])
                break;
        if (!i) // overspecified tree
             return AVERROR_INVALIDDATA;
        code = exit_at_level[i];
        exit_at_level[i] = 0;
        // construct code (append 0s to end) and introduce new exits
        for (j = i + 1 ;j <= bits[p]; ++j)
            exit_at_level[j] = code + (1u << (j - 1));
        codes[p] = code;
    }

    //no exits should be left (underspecified tree - ie. unused valid vlcs - not allowed by SPEC)
    for (p = 1; p < 33; p++)
        if (exit_at_level[p])
            return AVERROR_INVALIDDATA;

    return 0;
}

int ff_vorbis_ready_floor1_list(AVCodecContext *avctx,
                                vorbis_floor1_entry *list, int values)
{
    int i;
    list[0].sort = 0;
    list[1].sort = 1;
    for (i = 2; i < values; i++) {
        int j;
        list[i].low  = 0;
        list[i].high = 1;
        list[i].sort = i;
        for (j = 2; j < i; j++) {
            int tmp = list[j].x;
            if (tmp < list[i].x) {
                if (tmp > list[list[i].low].x)
                    list[i].low  =  j;
            } else {
                if (tmp < list[list[i].high].x)
                    list[i].high = j;
            }
        }
    }
    for (i = 0; i < values - 1; i++) {
        int j;
        for (j = i + 1; j < values; j++) {
            if (list[i].x == list[j].x) {
                av_log(avctx, AV_LOG_ERROR,
                       "Duplicate value found in floor 1 X coordinates\n");
                return AVERROR_INVALIDDATA;
            }
            if (list[list[i].sort].x > list[list[j].sort].x) {
                int tmp = list[i].sort;
                list[i].sort = list[j].sort;
                list[j].sort = tmp;
            }
        }
    }
    return 0;
}

static inline void render_line_unrolled(intptr_t x, int y, int x1,
                                        intptr_t sy, int ady, int adx,
                                        float *buf)
{
    int err = -adx;
    x -= x1 - 1;
    buf += x1 - 1;
    while (++x < 0) {
        err += ady;
        if (err >= 0) {
            err += ady - adx;
            y   += sy;
            buf[x++] = ff_vorbis_floor1_inverse_db_table[av_clip_uint8(y)];
        }
        buf[x] = ff_vorbis_floor1_inverse_db_table[av_clip_uint8(y)];
    }
    if (x <= 0) {
        if (err + ady >= 0)
            y += sy;
        buf[x] = ff_vorbis_floor1_inverse_db_table[av_clip_uint8(y)];
    }
}

static void render_line(int x0, int y0, int x1, int y1, float *buf)
{
    int dy  = y1 - y0;
    int adx = x1 - x0;
    int ady = FFABS(dy);
    int sy  = dy < 0 ? -1 : 1;
    buf[x0] = ff_vorbis_floor1_inverse_db_table[av_clip_uint8(y0)];
    if (ady*2 <= adx) { // optimized common case
        render_line_unrolled(x0, y0, x1, sy, ady, adx, buf);
    } else {
        int base  = dy / adx;
        int x     = x0;
        int y     = y0;
        int err   = -adx;
        ady -= FFABS(base) * adx;
        while (++x < x1) {
            y += base;
            err += ady;
            if (err >= 0) {
                err -= adx;
                y   += sy;
            }
            buf[x] = ff_vorbis_floor1_inverse_db_table[av_clip_uint8(y)];
        }
    }
}

void ff_vorbis_floor1_render_list(vorbis_floor1_entry * list, int values,
                                  uint16_t *y_list, int *flag,
                                  int multiplier, float *out, int samples)
{
    int lx, ly, i;
    lx = 0;
    ly = y_list[0] * multiplier;
    for (i = 1; i < values; i++) {
        int pos = list[i].sort;
        if (flag[pos]) {
            int x1 = list[pos].x;
            int y1 = y_list[pos] * multiplier;
            if (lx < samples)
                render_line(lx, ly, FFMIN(x1,samples), y1, out);
            lx = x1;
            ly = y1;
        }
        if (lx >= samples)
            break;
    }
    if (lx < samples)
        render_line(lx, ly, samples, ly, out);
}