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/*

 * RTP packetization for H.263 video

 * Copyright (c) 2012 Martin Storsjo

 *

 * 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

 */

#include "avformat.h"

#include "rtpenc.h"

#include "libavcodec/put_bits.h"

#include "libavcodec/get_bits.h"

struct H263Info {

    int src;

    int i;

    int u;

    int s;

    int a;

    int pb;

    int tr;

};

struct H263State {

    int gobn;

    int mba;

    int hmv1, vmv1, hmv2, vmv2;

    int quant;

};

static void send_mode_a(AVFormatContext *s1, const struct H263Info *info,

                        const uint8_t *buf, int len, int ebits, int m)

{

    RTPMuxContext *s = s1->priv_data;

    PutBitContext pb;

    init_put_bits(&pb, s->buf, 32);

    put_bits(&pb, 1, 0); /* F - 0, mode A */

    put_bits(&pb, 1, 0); /* P - 0, normal I/P */

    put_bits(&pb, 3, 0); /* SBIT - 0 bits */

    put_bits(&pb, 3, ebits); /* EBIT */

    put_bits(&pb, 3, info->src); /* SRC - source format */

    put_bits(&pb, 1, info->i); /* I - inter/intra */

    put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */

    put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */

    put_bits(&pb, 1, info->a); /* A - advanced prediction */

    put_bits(&pb, 4, 0); /* R - reserved */

    put_bits(&pb, 2, 0); /* DBQ - 0 */

    put_bits(&pb, 3, 0); /* TRB - 0 */

    put_bits(&pb, 8, info->tr); /* TR */

    flush_put_bits(&pb);

    memcpy(s->buf + 4, buf, len);

    ff_rtp_send_data(s1, s->buf, len + 4, m);

}

static void send_mode_b(AVFormatContext *s1, const struct H263Info *info,

                        const struct H263State *state, const uint8_t *buf,

                        int len, int sbits, int ebits, int m)

{

    RTPMuxContext *s = s1->priv_data;

    PutBitContext pb;

    init_put_bits(&pb, s->buf, 64);

    put_bits(&pb, 1, 1); /* F - 1, mode B */

    put_bits(&pb, 1, 0); /* P - 0, mode B */

    put_bits(&pb, 3, sbits); /* SBIT - 0 bits */

    put_bits(&pb, 3, ebits); /* EBIT - 0 bits */

    put_bits(&pb, 3, info->src); /* SRC - source format */

    put_bits(&pb, 5, state->quant); /* QUANT - quantizer for the first MB */

    put_bits(&pb, 5, state->gobn); /* GOBN - GOB number */

    put_bits(&pb, 9, state->mba); /* MBA - MB address */

    put_bits(&pb, 2, 0); /* R - reserved */

    put_bits(&pb, 1, info->i); /* I - inter/intra */

    put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */

    put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */

    put_bits(&pb, 1, info->a); /* A - advanced prediction */

    put_bits(&pb, 7, state->hmv1); /* HVM1 - horizontal motion vector 1 */

    put_bits(&pb, 7, state->vmv1); /* VMV1 - vertical motion vector 1 */

    put_bits(&pb, 7, state->hmv2); /* HVM2 - horizontal motion vector 2 */

    put_bits(&pb, 7, state->vmv2); /* VMV2 - vertical motion vector 2 */

    flush_put_bits(&pb);

    memcpy(s->buf + 8, buf, len);

    ff_rtp_send_data(s1, s->buf, len + 8, m);

}

void ff_rtp_send_h263_rfc2190(AVFormatContext *s1, const uint8_t *buf, int size,

                              const uint8_t *mb_info, int mb_info_size)

{

    RTPMuxContext *s = s1->priv_data;

    int len, sbits = 0, ebits = 0;

    GetBitContext gb;

    struct H263Info info = { 0 };

    struct H263State state = { 0 };

    int mb_info_pos = 0, mb_info_count = mb_info_size / 12;

    const uint8_t *buf_base = buf;

    s->timestamp = s->cur_timestamp;

    init_get_bits(&gb, buf, size*8);

    if (get_bits(&gb, 22) == 0x20) { /* Picture Start Code */

        info.tr  = get_bits(&gb, 8);

        skip_bits(&gb, 2); /* PTYPE start, H261 disambiguation */

        skip_bits(&gb, 3); /* Split screen, document camera, freeze picture release */

        info.src = get_bits(&gb, 3);

        info.i   = get_bits(&gb, 1);

        info.u   = get_bits(&gb, 1);

        info.s   = get_bits(&gb, 1);

        info.a   = get_bits(&gb, 1);

        info.pb  = get_bits(&gb, 1);

    }

    while (size > 0) {

        struct H263State packet_start_state = state;

        len = FFMIN(s->max_payload_size - 8, size);

        /* Look for a better place to split the frame into packets. */

        if (len < size) {

            const uint8_t *end = ff_h263_find_resync_marker_reverse(buf,

                                                                    buf + len);

            len = end - buf;

            if (len == s->max_payload_size - 8) {

                /* Skip mb info prior to the start of the current ptr */

                while (mb_info_pos < mb_info_count) {

                    uint32_t pos = AV_RL32(&mb_info[12*mb_info_pos])/8;

                    if (pos >= buf - buf_base)

                        break;

                    mb_info_pos++;

                }

                /* Find the first mb info past the end pointer */

                while (mb_info_pos + 1 < mb_info_count) {

                    uint32_t pos = AV_RL32(&mb_info[12*(mb_info_pos + 1)])/8;

                    if (pos >= end - buf_base)

                        break;

                    mb_info_pos++;

                }

                if (mb_info_pos < mb_info_count) {

                    const uint8_t *ptr = &mb_info[12*mb_info_pos];

                    uint32_t bit_pos = AV_RL32(ptr);

                    uint32_t pos = (bit_pos + 7)/8;

                    if (pos <= end - buf_base) {

                        state.quant = ptr[4];

                        state.gobn  = ptr[5];

                        state.mba   = AV_RL16(&ptr[6]);

                        state.hmv1  = (int8_t) ptr[8];

                        state.vmv1  = (int8_t) ptr[9];

                        state.hmv2  = (int8_t) ptr[10];

                        state.vmv2  = (int8_t) ptr[11];

                        ebits = 8 * pos - bit_pos;

                        len   = pos - (buf - buf_base);

                        mb_info_pos++;

                    } else {

                        av_log(s1, AV_LOG_ERROR,

                               "Unable to split H263 packet, use -mb_info %d "

                               "or lower.\n", s->max_payload_size - 8);

                    }

                } else {

                    av_log(s1, AV_LOG_ERROR, "Unable to split H263 packet, "

                           "use -mb_info %d or -ps 1.\n",

                           s->max_payload_size - 8);

                }

            }

        }

        if (size > 2 && !buf[0] && !buf[1])

            send_mode_a(s1, &info, buf, len, ebits, len == size);

        else

            send_mode_b(s1, &info, &packet_start_state, buf, len, sbits,

                        ebits, len == size);

        if (ebits) {

            sbits = 8 - ebits;

            len--;

        } else {

            sbits = 0;

        }

        buf  += len;

        size -= len;

        ebits = 0;

    }

}