ratecontrol.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

        s->lambda_table[mb_xy]= intq;
    }
}

void ff_get_2pass_fcode(MpegEncContext *s){
    RateControlContext *rcc= &s->rc_context;
    int picture_number= s->picture_number;
    RateControlEntry *rce;

    rce= &rcc->entry[picture_number];
    s->f_code= rce->f_code;
    s->b_code= rce->b_code;
}

//FIXME rd or at least approx for dquant

float ff_rate_estimate_qscale(MpegEncContext *s, int dry_run)
{
    float q;
    int qmin, qmax;
    float br_compensation;
    double diff;
    double short_term_q;
    double fps;
    int picture_number= s->picture_number;
    int64_t wanted_bits;
    RateControlContext *rcc= &s->rc_context;
    AVCodecContext *a= s->avctx;
    RateControlEntry local_rce, *rce;
    double bits;
    double rate_factor;
    int var;
    const int pict_type= s->pict_type;
    Picture * const pic= &s->current_picture;
    emms_c();

#ifdef CONFIG_LIBXVID
    if((s->flags&CODEC_FLAG_PASS2) && s->avctx->rc_strategy == FF_RC_STRATEGY_XVID)
        return ff_xvid_rate_estimate_qscale(s, dry_run);
#endif

    get_qminmax(&qmin, &qmax, s, pict_type);

    fps= 1/av_q2d(s->avctx->time_base);
//printf("input_pic_num:%d pic_num:%d frame_rate:%d\n", s->input_picture_number, s->picture_number, s->frame_rate);
        /* update predictors */
    if(picture_number>2 && !dry_run){
        const int last_var= s->last_pict_type == I_TYPE ? rcc->last_mb_var_sum : rcc->last_mc_mb_var_sum;
        update_predictor(&rcc->pred[s->last_pict_type], rcc->last_qscale, sqrt(last_var), s->frame_bits);
    }

    if(s->flags&CODEC_FLAG_PASS2){
        assert(picture_number>=0);
        assert(picture_number<rcc->num_entries);
        rce= &rcc->entry[picture_number];
        wanted_bits= rce->expected_bits;
    }else{
        Picture *dts_pic;
        rce= &local_rce;

        //FIXME add a dts field to AVFrame and ensure its set and use it here instead of reordering
        //but the reordering is simpler for now until h.264 b pyramid must be handeld
        if(s->pict_type == B_TYPE || s->low_delay)
            dts_pic= s->current_picture_ptr;
        else
            dts_pic= s->last_picture_ptr;

//if(dts_pic)
//            av_log(NULL, AV_LOG_ERROR, "%Ld %Ld %Ld %d\n", s->current_picture_ptr->pts, s->user_specified_pts, dts_pic->pts, picture_number);

        if(!dts_pic || dts_pic->pts == AV_NOPTS_VALUE)
            wanted_bits= (uint64_t)(s->bit_rate*(double)picture_number/fps);
        else
            wanted_bits= (uint64_t)(s->bit_rate*(double)dts_pic->pts/fps);
    }

    diff= s->total_bits - wanted_bits;
    br_compensation= (a->bit_rate_tolerance - diff)/a->bit_rate_tolerance;
    if(br_compensation<=0.0) br_compensation=0.001;

    var= pict_type == I_TYPE ? pic->mb_var_sum : pic->mc_mb_var_sum;

    short_term_q = 0; /* avoid warning */
    if(s->flags&CODEC_FLAG_PASS2){
        if(pict_type!=I_TYPE)
            assert(pict_type == rce->new_pict_type);

        q= rce->new_qscale / br_compensation;
//printf("%f %f %f last:%d var:%d type:%d//\n", q, rce->new_qscale, br_compensation, s->frame_bits, var, pict_type);
    }else{
        rce->pict_type=
        rce->new_pict_type= pict_type;
        rce->mc_mb_var_sum= pic->mc_mb_var_sum;
        rce->mb_var_sum   = pic->   mb_var_sum;
        rce->qscale   = FF_QP2LAMBDA * 2;
        rce->f_code   = s->f_code;
        rce->b_code   = s->b_code;
        rce->misc_bits= 1;

        bits= predict_size(&rcc->pred[pict_type], rce->qscale, sqrt(var));
        if(pict_type== I_TYPE){
            rce->i_count   = s->mb_num;
            rce->i_tex_bits= bits;
            rce->p_tex_bits= 0;
            rce->mv_bits= 0;
        }else{
            rce->i_count   = 0; //FIXME we do know this approx
            rce->i_tex_bits= 0;
            rce->p_tex_bits= bits*0.9;

            rce->mv_bits= bits*0.1;
        }
        rcc->i_cplx_sum [pict_type] += rce->i_tex_bits*rce->qscale;
        rcc->p_cplx_sum [pict_type] += rce->p_tex_bits*rce->qscale;
        rcc->mv_bits_sum[pict_type] += rce->mv_bits;
        rcc->frame_count[pict_type] ++;

        bits= rce->i_tex_bits + rce->p_tex_bits;
        rate_factor= rcc->pass1_wanted_bits/rcc->pass1_rc_eq_output_sum * br_compensation;

        q= get_qscale(s, rce, rate_factor, picture_number);
        if (q < 0)
            return -1;

        assert(q>0.0);
//printf("%f ", q);
        q= get_diff_limited_q(s, rce, q);
//printf("%f ", q);
        assert(q>0.0);

        if(pict_type==P_TYPE || s->intra_only){ //FIXME type dependent blur like in 2-pass
            rcc->short_term_qsum*=a->qblur;
            rcc->short_term_qcount*=a->qblur;

            rcc->short_term_qsum+= q;
            rcc->short_term_qcount++;
//printf("%f ", q);
            q= short_term_q= rcc->short_term_qsum/rcc->short_term_qcount;
//printf("%f ", q);
        }
        assert(q>0.0);

        q= modify_qscale(s, rce, q, picture_number);

        rcc->pass1_wanted_bits+= s->bit_rate/fps;

        assert(q>0.0);
    }

    if(s->avctx->debug&FF_DEBUG_RC){
        av_log(s->avctx, AV_LOG_DEBUG, "%c qp:%d<%2.1f<%d %d want:%d total:%d comp:%f st_q:%2.2f size:%d var:%d/%d br:%d fps:%d\n",
        av_get_pict_type_char(pict_type), qmin, q, qmax, picture_number, (int)wanted_bits/1000, (int)s->total_bits/1000,
        br_compensation, short_term_q, s->frame_bits, pic->mb_var_sum, pic->mc_mb_var_sum, s->bit_rate/1000, (int)fps
        );
    }

    if     (q<qmin) q=qmin;
    else if(q>qmax) q=qmax;

    if(s->adaptive_quant)
        adaptive_quantization(s, q);
    else
        q= (int)(q + 0.5);

    if(!dry_run){
        rcc->last_qscale= q;
        rcc->last_mc_mb_var_sum= pic->mc_mb_var_sum;
        rcc->last_mb_var_sum= pic->mb_var_sum;
    }
#if 0
{
    static int mvsum=0, texsum=0;
    mvsum += s->mv_bits;
    texsum += s->i_tex_bits + s->p_tex_bits;
    printf("%d %d//\n\n", mvsum, texsum);
}
#endif
    return q;
}

//----------------------------------------------
// 2-Pass code

static int init_pass2(MpegEncContext *s)
{
    RateControlContext *rcc= &s->rc_context;
    AVCodecContext *a= s->avctx;
    int i, toobig;
    double fps= 1/av_q2d(s->avctx->time_base);
    double complexity[5]={0,0,0,0,0};   // aproximate bits at quant=1
    uint64_t const_bits[5]={0,0,0,0,0}; // quantizer independent bits
    uint64_t all_const_bits;
    uint64_t all_available_bits= (uint64_t)(s->bit_rate*(double)rcc->num_entries/fps);
    double rate_factor=0;
    double step;
    //int last_i_frame=-10000000;
    const int filter_size= (int)(a->qblur*4) | 1;
    double expected_bits;
    double *qscale, *blured_qscale, qscale_sum;

    /* find complexity & const_bits & decide the pict_types */
    for(i=0; i<rcc->num_entries; i++){
        RateControlEntry *rce= &rcc->entry[i];

        rce->new_pict_type= rce->pict_type;
        rcc->i_cplx_sum [rce->pict_type] += rce->i_tex_bits*rce->qscale;
        rcc->p_cplx_sum [rce->pict_type] += rce->p_tex_bits*rce->qscale;
        rcc->mv_bits_sum[rce->pict_type] += rce->mv_bits;
        rcc->frame_count[rce->pict_type] ++;

        complexity[rce->new_pict_type]+= (rce->i_tex_bits+ rce->p_tex_bits)*(double)rce->qscale;
        const_bits[rce->new_pict_type]+= rce->mv_bits + rce->misc_bits;
    }
    all_const_bits= const_bits[I_TYPE] + const_bits[P_TYPE] + const_bits[B_TYPE];

    if(all_available_bits < all_const_bits){
        av_log(s->avctx, AV_LOG_ERROR, "requested bitrate is too low\n");
        return -1;
    }

    qscale= av_malloc(sizeof(double)*rcc->num_entries);
    blured_qscale= av_malloc(sizeof(double)*rcc->num_entries);
    toobig = 0;

    for(step=256*256; step>0.0000001; step*=0.5){
        expected_bits=0;
        rate_factor+= step;

        rcc->buffer_index= s->avctx->rc_buffer_size/2;

        /* find qscale */
        for(i=0; i<rcc->num_entries; i++){
            qscale[i]= get_qscale(s, &rcc->entry[i], rate_factor, i);
        }
        assert(filter_size%2==1);

        /* fixed I/B QP relative to P mode */
        for(i=rcc->num_entries-1; i>=0; i--){
            RateControlEntry *rce= &rcc->entry[i];

            qscale[i]= get_diff_limited_q(s, rce, qscale[i]);
        }

        /* smooth curve */
        for(i=0; i<rcc->num_entries; i++){
            RateControlEntry *rce= &rcc->entry[i];
            const int pict_type= rce->new_pict_type;
            int j;
            double q=0.0, sum=0.0;

            for(j=0; j<filter_size; j++){
                int index= i+j-filter_size/2;
                double d= index-i;
                double coeff= a->qblur==0 ? 1.0 : exp(-d*d/(a->qblur * a->qblur));

                if(index < 0 || index >= rcc->num_entries) continue;
                if(pict_type != rcc->entry[index].new_pict_type) continue;
                q+= qscale[index] * coeff;
                sum+= coeff;
            }
            blured_qscale[i]= q/sum;
        }

        /* find expected bits */
        for(i=0; i<rcc->num_entries; i++){
            RateControlEntry *rce= &rcc->entry[i];
            double bits;
            rce->new_qscale= modify_qscale(s, rce, blured_qscale[i], i);
            bits= qp2bits(rce, rce->new_qscale) + rce->mv_bits + rce->misc_bits;
//printf("%d %f\n", rce->new_bits, blured_qscale[i]);
            bits += 8*ff_vbv_update(s, bits);

            rce->expected_bits= expected_bits;
            expected_bits += bits;
        }

        /*
        av_log(s->avctx, AV_LOG_INFO,
            "expected_bits: %f all_available_bits: %d rate_factor: %f\n",
            expected_bits, (int)all_available_bits, rate_factor);
        */
        if(expected_bits > all_available_bits) {
            rate_factor-= step;
            ++toobig;
        }
    }
    av_free(qscale);
    av_free(blured_qscale);

    /* check bitrate calculations and print info */
    qscale_sum = 0.0;
    for(i=0; i<rcc->num_entries; i++){
        /* av_log(s->avctx, AV_LOG_DEBUG, "[lavc rc] entry[%d].new_qscale = %.3f  qp = %.3f\n",
            i, rcc->entry[i].new_qscale, rcc->entry[i].new_qscale / FF_QP2LAMBDA); */
        qscale_sum += av_clip(rcc->entry[i].new_qscale / FF_QP2LAMBDA, s->avctx->qmin, s->avctx->qmax);
    }
    assert(toobig <= 40);
    av_log(s->avctx, AV_LOG_DEBUG,
        "[lavc rc] requested bitrate: %d bps  expected bitrate: %d bps\n",
        s->bit_rate,
        (int)(expected_bits / ((double)all_available_bits/s->bit_rate)));
    av_log(s->avctx, AV_LOG_DEBUG,
        "[lavc rc] estimated target average qp: %.3f\n",
        (float)qscale_sum / rcc->num_entries);
    if (toobig == 0) {
        av_log(s->avctx, AV_LOG_INFO,
            "[lavc rc] Using all of requested bitrate is not "
            "necessary for this video with these parameters.\n");
    } else if (toobig == 40) {
        av_log(s->avctx, AV_LOG_ERROR,
            "[lavc rc] Error: bitrate too low for this video "
            "with these parameters.\n");
        return -1;
    } else if (fabs(expected_bits/all_available_bits - 1.0) > 0.01) {
        av_log(s->avctx, AV_LOG_ERROR,
            "[lavc rc] Error: 2pass curve failed to converge\n");
        return -1;
    }

    return 0;
}