/*

 * 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 "mpegvideoenc.h"

#include "put_bits.h"

#define H261_MAX_RUN   26

#define H261_MAX_LEVEL 15

#define H261_ESC_LEN   (6 + 6 + 8)

#define MV_TAB_OFFSET  32

static struct VLCLUT {

    uint8_t len;

    uint16_t code;

} vlc_lut[H261_MAX_RUN + 1][32 /* 0..2 * H261_MAX_LEN are used */];

// Not const despite never being initialized because doing so would

// put it into .rodata instead of .bss and bloat the binary.

// mv_penalty exists so that the motion estimation code can avoid branches.

static uint8_t mv_penalty[MAX_FCODE + 1][MAX_DMV * 2 + 1];

static uint8_t uni_h261_rl_len     [64 * 128];

static uint8_t uni_h261_rl_len_last[64 * 128];

static uint8_t h261_mv_codes[64][2];

typedef struct H261EncContext {

    MPVMainEncContext s;

    int gob_number;

    enum {

        H261_QCIF = 0,

        H261_CIF  = 1,

    } format;

} H261EncContext;

static int h261_encode_picture_header(MPVMainEncContext *const m)

{

    H261EncContext *const h = (H261EncContext *)m;

    MPVEncContext *const s = &h->s.s;

    int temp_ref;

    put_bits_assume_flushed(&s->pb);

    put_bits(&s->pb, 20, 0x10); /* PSC */

    temp_ref = s->picture_number * 30000LL * s->c.avctx->time_base.num /

               (1001LL * s->c.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->c.pict_type == AV_PICTURE_TYPE_I); /* freeze picture release on/off */

    put_bits(&s->pb, 1, h->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 */

    h->gob_number = h->format - 1;

    s->mb_skip_run = 0;

    return 0;

}

/**

 * Encode a group of blocks header.

 */

static void h261_encode_gob_header(MPVEncContext *const s, int mb_line)

{

    H261EncContext *const h = (H261EncContext *)s;

    if (h->format == H261_QCIF) {

        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->c.qscale);     /* GQUANT */

    put_bits(&s->pb, 1, 0);             /* no GEI */

    s->mb_skip_run = 0;

    s->c.last_mv[0][0][0] = 0;

    s->c.last_mv[0][0][1] = 0;

}

void ff_h261_reorder_mb_index(MPVEncContext *const s)

{

    const H261EncContext *const h = (H261EncContext*)s;

    int index = s->c.mb_x + s->c.mb_y * s->c.mb_width;

    if (index % 11 == 0) {

        if (index % 33 == 0)

            h261_encode_gob_header(s, 0);

        s->c.last_mv[0][0][0] = 0;

        s->c.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 (h->format == H261_CIF) {

        s->c.mb_x  = index % 11;

        index   /= 11;

        s->c.mb_y  = index % 3;

        index   /= 3;

        s->c.mb_x += 11 * (index % 2);

        index   /= 2;

        s->c.mb_y += 3 * index;

        ff_init_block_index(&s->c);

        ff_update_block_index(&s->c, 8, 0, 1);

    }

}

static void h261_encode_motion(PutBitContext *pb, int val)

{

    put_bits(pb, h261_mv_codes[MV_TAB_OFFSET + val][1],

                 h261_mv_codes[MV_TAB_OFFSET + val][0]);

}

static inline int get_cbp(const int block_last_index[6])

{

    int i, cbp;

    cbp = 0;

    for (i = 0; i < 6; i++)

        if (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)

{

    MPVEncContext *const s = &h->s.s;

    int level, run, i, j, last_index, last_non_zero;

    if (s->c.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->c.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->c.block_last_index[n];

    last_non_zero = i - 1;

    for (; i <= last_index; i++) {

        j     = s->c.intra_scantable.permutated[i];

        level = block[j];

        if (level) {

            run    = i - last_non_zero - 1;

            if (run <= H261_MAX_RUN &&

                (unsigned)(level + H261_MAX_LEVEL) <= 2 * H261_MAX_LEVEL &&

                vlc_lut[run][level + H261_MAX_LEVEL].len) {

                put_bits(&s->pb, vlc_lut[run][level + H261_MAX_LEVEL].len,

                         vlc_lut[run][level + H261_MAX_LEVEL].code);

            } else {

                /* Escape */

                put_bits(&s->pb, 6 + 6, (1 << 6) | run);

                av_assert1(level != 0);

                av_assert1(FFABS(level) <= 127);

                put_sbits(&s->pb, 8, level);

            }

            last_non_zero = i;

        }

    }

    if (last_index > -1)

        put_bits(&s->pb, 2, 0x2); // EOB

}

static void h261_encode_mb(MPVEncContext *const 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;

    int mvd, mv_diff_x, mv_diff_y, i, cbp;

    cbp = 63; // avoid warning

    mvd = 0;

    s->c.mtype = 0;

    if (!s->c.mb_intra) {

        /* compute cbp */

        cbp = get_cbp(s->c.block_last_index);

        /* mvd indicates if this block is motion compensated */

        mvd = motion_x | motion_y;

        if ((cbp | mvd) == 0) {

            /* skip macroblock */

            s->mb_skip_run++;

            s->c.last_mv[0][0][0] = 0;

            s->c.last_mv[0][0][1] = 0;

            s->c.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->c.mb_intra) {

        s->c.mtype++;

        if (mvd || s->loop_filter)

            s->c.mtype += 3;

        if (s->loop_filter)

            s->c.mtype += 3;

        if (cbp)

            s->c.mtype++;

        av_assert1(s->c.mtype > 1);

    }

    if (s->dquant && cbp) {

        s->c.mtype++;

    } else

        s->c.qscale -= s->dquant;

    put_bits(&s->pb,

             ff_h261_mtype_bits[s->c.mtype],

             ff_h261_mtype_code[s->c.mtype]);

    s->c.mtype = ff_h261_mtype_map[s->c.mtype];

    if (IS_QUANT(s->c.mtype)) {

        ff_set_qscale(&s->c, s->c.qscale + s->dquant);

        put_bits(&s->pb, 5, s->c.qscale);

    }

    if (IS_16X16(s->c.mtype)) {

        mv_diff_x       = (motion_x >> 1) - s->c.last_mv[0][0][0];

        mv_diff_y       = (motion_y >> 1) - s->c.last_mv[0][0][1];

        s->c.last_mv[0][0][0] = (motion_x >> 1);

        s->c.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(s->c.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(s->c.mtype)) {

        s->c.last_mv[0][0][0] = 0;

        s->c.last_mv[0][0][1] = 0;

    }

}

static av_cold void h261_encode_init_static(void)

{

    uint8_t (*const mv_codes)[2] = h261_mv_codes + MV_TAB_OFFSET;

    memset(uni_h261_rl_len,      H261_ESC_LEN, sizeof(uni_h261_rl_len));

    memset(uni_h261_rl_len_last, H261_ESC_LEN + 2 /* EOB */, sizeof(uni_h261_rl_len_last));

    // The following loop is over the ordinary elements, not EOB or escape.

    for (size_t i = 1; i < FF_ARRAY_ELEMS(ff_h261_tcoeff_vlc) - 1; i++) {

        unsigned run   = ff_h261_tcoeff_run[i];

        unsigned level = ff_h261_tcoeff_level[i];

        unsigned len   = ff_h261_tcoeff_vlc[i][1] + 1 /* sign */;

        unsigned code  = ff_h261_tcoeff_vlc[i][0];

        vlc_lut[run][H261_MAX_LEVEL + level] = (struct VLCLUT){ len, code << 1 };

        vlc_lut[run][H261_MAX_LEVEL - level] = (struct VLCLUT){ len, (code << 1) | 1 };

        uni_h261_rl_len     [UNI_AC_ENC_INDEX(run, 64 + level)] = len;

        uni_h261_rl_len     [UNI_AC_ENC_INDEX(run, 64 - level)] = len;

        uni_h261_rl_len_last[UNI_AC_ENC_INDEX(run, 64 + level)] = len + 2;

        uni_h261_rl_len_last[UNI_AC_ENC_INDEX(run, 64 - level)] = len + 2;

    }

    for (ptrdiff_t i = 1;; i++) {

        // sign-one MV codes; diff -16..-1, 16..31

        mv_codes[32 - i][0] = mv_codes[-i][0] = (ff_h261_mv_tab[i][0] << 1) | 1 /* sign */;

        mv_codes[32 - i][1] = mv_codes[-i][1] = ff_h261_mv_tab[i][1] + 1;

        if (i == 16)

            break;

        // sign-zero MV codes: diff -31..-17, 1..15

        mv_codes[i][0] = mv_codes[i - 32][0] = ff_h261_mv_tab[i][0] << 1;

        mv_codes[i][1] = mv_codes[i - 32][1] = ff_h261_mv_tab[i][1] + 1;

    }

    // MV code for difference zero; has no sign

    mv_codes[0][0] = 1;

    mv_codes[0][1] = 1;

}

static av_cold int h261_encode_init(AVCodecContext *avctx)

{

    static AVOnce init_static_once = AV_ONCE_INIT;

    H261EncContext *const h = avctx->priv_data;

    MPVEncContext *const s = &h->s.s;

    if (avctx->width == 176 && avctx->height == 144) {

        h->format = H261_QCIF;

    } else if (avctx->width == 352 && avctx->height == 288) {

        h->format = H261_CIF;

    } else {

        av_log(avctx, AV_LOG_ERROR,

                "The specified picture size of %dx%d is not valid for the "

                "H.261 codec.\nValid sizes are 176x144, 352x288\n",

               avctx->width, avctx->height);

        return AVERROR(EINVAL);

    }

    h->s.encode_picture_header = h261_encode_picture_header;

    s->encode_mb               = h261_encode_mb;

    s->min_qcoeff       = -127;

    s->max_qcoeff       = 127;

    s->ac_esc_length    = H261_ESC_LEN;

    s->me.mv_penalty = mv_penalty;

    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_last;

    ff_thread_once(&init_static_once, h261_encode_init_static);

    return ff_mpv_encode_init(avctx);

}

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,

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,

    .priv_data_size = sizeof(H261EncContext),

    .init           = h261_encode_init,

    FF_CODEC_ENCODE_CB(ff_mpv_encode_picture),

    .close          = ff_mpv_encode_end,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

    CODEC_PIXFMTS(AV_PIX_FMT_YUV420P),

    .color_ranges   = AVCOL_RANGE_MPEG,

};