h261enc.c

Go to the documentation of this file.

/*
 * H.261 encoder
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 * Copyright (c) 2004 Maarten Daniels
 *
 * 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
 * H.261 encoder.
 */
 
#include "libavutil/attributes.h"
#include "libavutil/avassert.h"
#include "libavutil/thread.h"
#include "avcodec.h"
#include "codec_internal.h"
#include "mpegutils.h"
#include "mpegvideo.h"
#include "h261.h"
#include "h261enc.h"
#include "mpegvideodata.h"
#include "mpegvideoenc.h"
 
static uint8_t uni_h261_rl_len [64*64*2*2];
#define UNI_ENC_INDEX(last,run,level) ((last)*128*64 + (run)*128 + (level))
 
typedef struct H261EncContext {
    MpegEncContext s;
 
    H261Context common;
 
    int gob_number;
} H261EncContext;
 
int ff_h261_get_picture_format(int width, int height)
{
    // QCIF
    if (width == 176 && height == 144)
        return 0;
    // CIF
    else if (width == 352 && height == 288)
        return 1;
    // ERROR
    else
        return AVERROR(EINVAL);
}
 
void ff_h261_encode_picture_header(MpegEncContext *s, int picture_number)
{
    H261EncContext *const h = (H261EncContext *)s;
    int format, temp_ref;
 
    align_put_bits(&s->pb);
 
    /* Update the pointer to last GOB */
    s->ptr_lastgob = put_bits_ptr(&s->pb);
 
    put_bits(&s->pb, 20, 0x10); /* PSC */
 
    temp_ref = s->picture_number * 30000LL * s->avctx->time_base.num /
               (1001LL * s->avctx->time_base.den);   // FIXME maybe this should use a timestamp
    put_sbits(&s->pb, 5, temp_ref); /* TemporalReference */
 
    put_bits(&s->pb, 1, 0); /* split screen off */
    put_bits(&s->pb, 1, 0); /* camera  off */
    put_bits(&s->pb, 1, s->pict_type == AV_PICTURE_TYPE_I); /* freeze picture release on/off */
 
    format = ff_h261_get_picture_format(s->width, s->height);
 
    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
 
    put_bits(&s->pb, 1, 1); /* still image mode */
    put_bits(&s->pb, 1, 1); /* reserved */
 
    put_bits(&s->pb, 1, 0); /* no PEI */
    if (format == 0)
        h->gob_number = -1;
    else
        h->gob_number = 0;
    s->mb_skip_run = 0;
}
 
/**
 * Encode a group of blocks header.
 */
static void h261_encode_gob_header(MpegEncContext *s, int mb_line)
{
    H261EncContext *const h = (H261EncContext *)s;
    if (ff_h261_get_picture_format(s->width, s->height) == 0) {
        h->gob_number += 2; // QCIF
    } else {
        h->gob_number++;    // CIF
    }
    put_bits(&s->pb, 16, 1);            /* GBSC */
    put_bits(&s->pb, 4, h->gob_number); /* GN */
    put_bits(&s->pb, 5, s->qscale);     /* GQUANT */
    put_bits(&s->pb, 1, 0);             /* no GEI */
    s->mb_skip_run = 0;
    s->last_mv[0][0][0] = 0;
    s->last_mv[0][0][1] = 0;
}
 
void ff_h261_reorder_mb_index(MpegEncContext *s)
{
    int index = s->mb_x + s->mb_y * s->mb_width;
 
    if (index % 11 == 0) {
        if (index % 33 == 0)
            h261_encode_gob_header(s, 0);
        s->last_mv[0][0][0] = 0;
        s->last_mv[0][0][1] = 0;
    }
 
    /* for CIF the GOB's are fragmented in the middle of a scanline
     * that's why we need to adjust the x and y index of the macroblocks */
    if (ff_h261_get_picture_format(s->width, s->height) == 1) { // CIF
        s->mb_x  = index % 11;
        index   /= 11;
        s->mb_y  = index % 3;
        index   /= 3;
        s->mb_x += 11 * (index % 2);
        index   /= 2;
        s->mb_y += 3 * index;
 
        ff_init_block_index(s);
        ff_update_block_index(s, 8, 0, 1);
    }
}
 
static void h261_encode_motion(PutBitContext *pb, int val)
{
    int sign, code;
    if (val == 0) {
        code = 0;
        put_bits(pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
    } else {
        if (val > 15)
            val -= 32;
        if (val < -16)
            val += 32;
        sign = val < 0;
        code = sign ? -val : val;
        put_bits(pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
        put_bits(pb, 1, sign);
    }
}
 
static inline int get_cbp(MpegEncContext *s, int16_t block[6][64])
{
    int i, cbp;
    cbp = 0;
    for (i = 0; i < 6; i++)
        if (s->block_last_index[i] >= 0)
            cbp |= 1 << (5 - i);
    return cbp;
}
 
/**
 * Encode an 8x8 block.
 * @param block the 8x8 block
 * @param n block index (0-3 are luma, 4-5 are chroma)
 */
static void h261_encode_block(H261EncContext *h, int16_t *block, int n)
{
    MpegEncContext *const s = &h->s;
    int level, run, i, j, last_index, last_non_zero, sign, slevel, code;
    RLTable *rl;
 
    rl = &ff_h261_rl_tcoeff;
    if (s->mb_intra) {
        /* DC coef */
        level = block[0];
        /* 255 cannot be represented, so we clamp */
        if (level > 254) {
            level    = 254;
            block[0] = 254;
        }
        /* 0 cannot be represented also */
        else if (level < 1) {
            level    = 1;
            block[0] = 1;
        }
        if (level == 128)
            put_bits(&s->pb, 8, 0xff);
        else
            put_bits(&s->pb, 8, level);
        i = 1;
    } else if ((block[0] == 1 || block[0] == -1) &&
               (s->block_last_index[n] > -1)) {
        // special case
        put_bits(&s->pb, 2, block[0] > 0 ? 2 : 3);
        i = 1;
    } else {
        i = 0;
    }
 
    /* AC coefs */
    last_index    = s->block_last_index[n];
    last_non_zero = i - 1;
    for (; i <= last_index; i++) {
        j     = s->intra_scantable.permutated[i];
        level = block[j];
        if (level) {
            run    = i - last_non_zero - 1;
            sign   = 0;
            slevel = level;
            if (level < 0) {
                sign  = 1;
                level = -level;
            }
            code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/,
                                run, level);
            if (run == 0 && level < 16)
                code += 1;
            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
            if (code == rl->n) {
                put_bits(&s->pb, 6, run);
                av_assert1(slevel != 0);
                av_assert1(level <= 127);
                put_sbits(&s->pb, 8, slevel);
            } else {
                put_bits(&s->pb, 1, sign);
            }
            last_non_zero = i;
        }
    }
    if (last_index > -1)
        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]); // EOB
}
 
void ff_h261_encode_mb(MpegEncContext *s, int16_t block[6][64],
                       int motion_x, int motion_y)
{
    /* The following is only allowed because this encoder
     * does not use slice threading. */
    H261EncContext *const h = (H261EncContext *)s;
    H261Context *const com = &h->common;
    int mvd, mv_diff_x, mv_diff_y, i, cbp;
    cbp = 63; // avoid warning
    mvd = 0;
 
    com->mtype = 0;
 
    if (!s->mb_intra) {
        /* compute cbp */
        cbp = get_cbp(s, block);
 
        /* mvd indicates if this block is motion compensated */
        mvd = motion_x | motion_y;
 
        if ((cbp | mvd) == 0) {
            /* skip macroblock */
            s->skip_count++;
            s->mb_skip_run++;
            s->last_mv[0][0][0] = 0;
            s->last_mv[0][0][1] = 0;
            s->qscale -= s->dquant;
            return;
        }
    }
 
    /* MB is not skipped, encode MBA */
    put_bits(&s->pb,
             ff_h261_mba_bits[s->mb_skip_run],
             ff_h261_mba_code[s->mb_skip_run]);
    s->mb_skip_run = 0;
 
    /* calculate MTYPE */
    if (!s->mb_intra) {
        com->mtype++;
 
        if (mvd || s->loop_filter)
            com->mtype += 3;
        if (s->loop_filter)
            com->mtype += 3;
        if (cbp)
            com->mtype++;
        av_assert1(com->mtype > 1);
    }
 
    if (s->dquant && cbp) {
        com->mtype++;
    } else
        s->qscale -= s->dquant;
 
    put_bits(&s->pb,
             ff_h261_mtype_bits[com->mtype],
             ff_h261_mtype_code[com->mtype]);
 
    com->mtype = ff_h261_mtype_map[com->mtype];
 
    if (IS_QUANT(com->mtype)) {
        ff_set_qscale(s, s->qscale + s->dquant);
        put_bits(&s->pb, 5, s->qscale);
    }
 
    if (IS_16X16(com->mtype)) {
        mv_diff_x       = (motion_x >> 1) - s->last_mv[0][0][0];
        mv_diff_y       = (motion_y >> 1) - s->last_mv[0][0][1];
        s->last_mv[0][0][0] = (motion_x >> 1);
        s->last_mv[0][0][1] = (motion_y >> 1);
        h261_encode_motion(&s->pb, mv_diff_x);
        h261_encode_motion(&s->pb, mv_diff_y);
    }
 
    if (HAS_CBP(com->mtype)) {
        av_assert1(cbp > 0);
        put_bits(&s->pb,
                 ff_h261_cbp_tab[cbp - 1][1],
                 ff_h261_cbp_tab[cbp - 1][0]);
    }
    for (i = 0; i < 6; i++)
        /* encode each block */
        h261_encode_block(h, block[i], i);
 
    if (!IS_16X16(com->mtype)) {
        s->last_mv[0][0][0] = 0;
        s->last_mv[0][0][1] = 0;
    }
}
 
static av_cold void init_uni_h261_rl_tab(const RLTable *rl, uint8_t *len_tab)
{
    int slevel, run, last;
 
    av_assert0(MAX_LEVEL >= 64);
    av_assert0(MAX_RUN   >= 63);
 
    for(slevel=-64; slevel<64; slevel++){
        if(slevel==0) continue;
        for(run=0; run<64; run++){
            for(last=0; last<=1; last++){
                const int index= UNI_ENC_INDEX(last, run, slevel+64);
                int level= slevel < 0 ? -slevel : slevel;
                int len, code;
 
                len_tab[index]= 100;
 
                /* ESC0 */
                code= get_rl_index(rl, 0, run, level);
                len=  rl->table_vlc[code][1] + 1;
                if(last)
                    len += 2;
 
                if(code!=rl->n && len < len_tab[index]){
                    len_tab [index]= len;
                }
                /* ESC */
                len = rl->table_vlc[rl->n][1];
                if(last)
                    len += 2;
 
                if(len < len_tab[index]){
                    len_tab [index]= len;
                }
            }
        }
    }
}
 
static av_cold void h261_encode_init_static(void)
{
    static uint8_t h261_rl_table_store[2][2 * MAX_RUN + MAX_LEVEL + 3];
 
    ff_rl_init(&ff_h261_rl_tcoeff, h261_rl_table_store);
    init_uni_h261_rl_tab(&ff_h261_rl_tcoeff, uni_h261_rl_len);
}
 
av_cold void ff_h261_encode_init(MpegEncContext *s)
{
    H261EncContext *const h = (H261EncContext*)s;
    static AVOnce init_static_once = AV_ONCE_INIT;
 
    s->private_ctx = &h->common;
 
    s->min_qcoeff       = -127;
    s->max_qcoeff       = 127;
    s->y_dc_scale_table =
    s->c_dc_scale_table = ff_mpeg1_dc_scale_table;
    s->ac_esc_length    = 6+6+8;
 
    s->intra_ac_vlc_length      = s->inter_ac_vlc_length      = uni_h261_rl_len;
    s->intra_ac_vlc_last_length = s->inter_ac_vlc_last_length = uni_h261_rl_len + 128*64;
    ff_thread_once(&init_static_once, h261_encode_init_static);
}
 
const FFCodec ff_h261_encoder = {
    .p.name         = "h261",
    CODEC_LONG_NAME("H.261"),
    .p.type         = AVMEDIA_TYPE_VIDEO,
    .p.id           = AV_CODEC_ID_H261,
    .p.priv_class   = &ff_mpv_enc_class,
    .priv_data_size = sizeof(H261EncContext),
    .init           = ff_mpv_encode_init,
    FF_CODEC_ENCODE_CB(ff_mpv_encode_picture),
    .close          = ff_mpv_encode_end,
    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,
    .p.pix_fmts     = (const enum AVPixelFormat[]) { AV_PIX_FMT_YUV420P,
                                                     AV_PIX_FMT_NONE },
};