FFmpeg/libswresample/resample_template.c

/*
 * audio resampling
 * Copyright (c) 2004-2012 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 * audio resampling
 * @author Michael Niedermayer <michaelni@gmx.at>
 */

int RENAME(swri_resample)(ResampleContext *c, DELEM *dst, const DELEM *src, int *consumed, int src_size, int dst_size, int update_ctx){
    int dst_index, i;
    int index= c->index;
    int frac= c->frac;
    int dst_incr_frac= c->dst_incr % c->src_incr;
    int dst_incr=      c->dst_incr / c->src_incr;
    int compensation_distance= c->compensation_distance;

    av_assert1(c->filter_shift == FILTER_SHIFT);
    av_assert1(c->felem_size == sizeof(FELEM));

    if(compensation_distance == 0 && c->filter_length == 1 && c->phase_shift==0){
        int64_t index2= ((int64_t)index)<<32;
        int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr;
        dst_size= FFMIN(dst_size, (src_size-1-index) * (int64_t)c->src_incr / c->dst_incr);

        for(dst_index=0; dst_index < dst_size; dst_index++){
            dst[dst_index] = src[index2>>32];
            index2 += incr;
        }
        index += dst_index * dst_incr;
        index += (frac + dst_index * (int64_t)dst_incr_frac) / c->src_incr;
        frac   = (frac + dst_index * (int64_t)dst_incr_frac) % c->src_incr;
    }else{
        for(dst_index=0; dst_index < dst_size; dst_index++){
            FELEM *filter= ((FELEM*)c->filter_bank) + c->filter_length*(index & c->phase_mask);
            int sample_index= index >> c->phase_shift;
            FELEM2 val=0;

            if(sample_index + c->filter_length > src_size || -sample_index >= src_size){
                break;
            }else if(sample_index < 0){
                for(i=0; i<c->filter_length; i++)
                    val += src[FFABS(sample_index + i)] * filter[i];
            }else if(c->linear){
                FELEM2 v2=0;
                for(i=0; i<c->filter_length; i++){
                    val += src[sample_index + i] * (FELEM2)filter[i];
                    v2  += src[sample_index + i] * (FELEM2)filter[i + c->filter_length];
                }
                val+=(v2-val)*(FELEML)frac / c->src_incr;
            }else{
                for(i=0; i<c->filter_length; i++){
                    val += src[sample_index + i] * (FELEM2)filter[i];
                }
            }

            OUT(dst[dst_index], val);

            frac += dst_incr_frac;
            index += dst_incr;
            if(frac >= c->src_incr){
                frac -= c->src_incr;
                index++;
            }

            if(dst_index + 1 == compensation_distance){
                compensation_distance= 0;
                dst_incr_frac= c->ideal_dst_incr % c->src_incr;
                dst_incr=      c->ideal_dst_incr / c->src_incr;
            }
        }
    }
    *consumed= FFMAX(index, 0) >> c->phase_shift;
    if(index>=0) index &= c->phase_mask;

    if(compensation_distance){
        compensation_distance -= dst_index;
        assert(compensation_distance > 0);
    }
    if(update_ctx){
        c->frac= frac;
        c->index= index;
        c->dst_incr= dst_incr_frac + c->src_incr*dst_incr;
        c->compensation_distance= compensation_distance;
    }
#if 0
    if(update_ctx && !c->compensation_distance){
#undef rand
        av_resample_compensate(c, rand() % (8000*2) - 8000, 8000*2);
av_log(NULL, AV_LOG_DEBUG, "%d %d %d\n", c->dst_incr, c->ideal_dst_incr, c->compensation_distance);
    }
#endif

    return dst_index;
}