1/*
2 * RTP packetization for H.263 video
3 * Copyright (c) 2012 Martin Storsjo
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22#include "avformat.h"
23#include "rtpenc.h"
24#include "libavcodec/put_bits.h"
25#include "libavcodec/get_bits.h"
26
27struct H263Info {
28    int src;
29    int i;
30    int u;
31    int s;
32    int a;
33    int pb;
34    int tr;
35};
36
37struct H263State {
38    int gobn;
39    int mba;
40    int hmv1, vmv1, hmv2, vmv2;
41    int quant;
42};
43
44static void send_mode_a(AVFormatContext *s1, const struct H263Info *info,
45                        const uint8_t *buf, int len, int ebits, int m)
46{
47    RTPMuxContext *s = s1->priv_data;
48    PutBitContext pb;
49
50    init_put_bits(&pb, s->buf, 32);
51    put_bits(&pb, 1, 0); /* F - 0, mode A */
52    put_bits(&pb, 1, 0); /* P - 0, normal I/P */
53    put_bits(&pb, 3, 0); /* SBIT - 0 bits */
54    put_bits(&pb, 3, ebits); /* EBIT */
55    put_bits(&pb, 3, info->src); /* SRC - source format */
56    put_bits(&pb, 1, info->i); /* I - inter/intra */
57    put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */
58    put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */
59    put_bits(&pb, 1, info->a); /* A - advanced prediction */
60    put_bits(&pb, 4, 0); /* R - reserved */
61    put_bits(&pb, 2, 0); /* DBQ - 0 */
62    put_bits(&pb, 3, 0); /* TRB - 0 */
63    put_bits(&pb, 8, info->tr); /* TR */
64    flush_put_bits(&pb);
65    memcpy(s->buf + 4, buf, len);
66
67    ff_rtp_send_data(s1, s->buf, len + 4, m);
68}
69
70static void send_mode_b(AVFormatContext *s1, const struct H263Info *info,
71                        const struct H263State *state, const uint8_t *buf,
72                        int len, int sbits, int ebits, int m)
73{
74    RTPMuxContext *s = s1->priv_data;
75    PutBitContext pb;
76
77    init_put_bits(&pb, s->buf, 64);
78    put_bits(&pb, 1, 1); /* F - 1, mode B */
79    put_bits(&pb, 1, 0); /* P - 0, mode B */
80    put_bits(&pb, 3, sbits); /* SBIT - 0 bits */
81    put_bits(&pb, 3, ebits); /* EBIT - 0 bits */
82    put_bits(&pb, 3, info->src); /* SRC - source format */
83    put_bits(&pb, 5, state->quant); /* QUANT - quantizer for the first MB */
84    put_bits(&pb, 5, state->gobn); /* GOBN - GOB number */
85    put_bits(&pb, 9, state->mba); /* MBA - MB address */
86    put_bits(&pb, 2, 0); /* R - reserved */
87    put_bits(&pb, 1, info->i); /* I - inter/intra */
88    put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */
89    put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */
90    put_bits(&pb, 1, info->a); /* A - advanced prediction */
91    put_bits(&pb, 7, state->hmv1); /* HVM1 - horizontal motion vector 1 */
92    put_bits(&pb, 7, state->vmv1); /* VMV1 - vertical motion vector 1 */
93    put_bits(&pb, 7, state->hmv2); /* HVM2 - horizontal motion vector 2 */
94    put_bits(&pb, 7, state->vmv2); /* VMV2 - vertical motion vector 2 */
95    flush_put_bits(&pb);
96    memcpy(s->buf + 8, buf, len);
97
98    ff_rtp_send_data(s1, s->buf, len + 8, m);
99}
100
101void ff_rtp_send_h263_rfc2190(AVFormatContext *s1, const uint8_t *buf, int size,
102                              const uint8_t *mb_info, int mb_info_size)
103{
104    RTPMuxContext *s = s1->priv_data;
105    int len, sbits = 0, ebits = 0;
106    GetBitContext gb;
107    struct H263Info info = { 0 };
108    struct H263State state = { 0 };
109    int mb_info_pos = 0, mb_info_count = mb_info_size / 12;
110    const uint8_t *buf_base = buf;
111
112    s->timestamp = s->cur_timestamp;
113
114    init_get_bits(&gb, buf, size*8);
115    if (get_bits(&gb, 22) == 0x20) { /* Picture Start Code */
116        info.tr  = get_bits(&gb, 8);
117        skip_bits(&gb, 2); /* PTYPE start, H261 disambiguation */
118        skip_bits(&gb, 3); /* Split screen, document camera, freeze picture release */
119        info.src = get_bits(&gb, 3);
120        info.i   = get_bits(&gb, 1);
121        info.u   = get_bits(&gb, 1);
122        info.s   = get_bits(&gb, 1);
123        info.a   = get_bits(&gb, 1);
124        info.pb  = get_bits(&gb, 1);
125    }
126
127    while (size > 0) {
128        struct H263State packet_start_state = state;
129        len = FFMIN(s->max_payload_size - 8, size);
130
131        /* Look for a better place to split the frame into packets. */
132        if (len < size) {
133            const uint8_t *end = ff_h263_find_resync_marker_reverse(buf,
134                                                                    buf + len);
135            len = end - buf;
136            if (len == s->max_payload_size - 8) {
137                /* Skip mb info prior to the start of the current ptr */
138                while (mb_info_pos < mb_info_count) {
139                    uint32_t pos = AV_RL32(&mb_info[12*mb_info_pos])/8;
140                    if (pos >= buf - buf_base)
141                        break;
142                    mb_info_pos++;
143                }
144                /* Find the first mb info past the end pointer */
145                while (mb_info_pos + 1 < mb_info_count) {
146                    uint32_t pos = AV_RL32(&mb_info[12*(mb_info_pos + 1)])/8;
147                    if (pos >= end - buf_base)
148                        break;
149                    mb_info_pos++;
150                }
151                if (mb_info_pos < mb_info_count) {
152                    const uint8_t *ptr = &mb_info[12*mb_info_pos];
153                    uint32_t bit_pos = AV_RL32(ptr);
154                    uint32_t pos = (bit_pos + 7)/8;
155                    if (pos <= end - buf_base) {
156                        state.quant = ptr[4];
157                        state.gobn  = ptr[5];
158                        state.mba   = AV_RL16(&ptr[6]);
159                        state.hmv1  = (int8_t) ptr[8];
160                        state.vmv1  = (int8_t) ptr[9];
161                        state.hmv2  = (int8_t) ptr[10];
162                        state.vmv2  = (int8_t) ptr[11];
163                        ebits = 8 * pos - bit_pos;
164                        len   = pos - (buf - buf_base);
165                        mb_info_pos++;
166                    } else {
167                        av_log(s1, AV_LOG_ERROR,
168                               "Unable to split H263 packet, use -mb_info %d "
169                               "or lower.\n", s->max_payload_size - 8);
170                    }
171                } else {
172                    av_log(s1, AV_LOG_ERROR, "Unable to split H263 packet, "
173                           "use -mb_info %d or -ps 1.\n",
174                           s->max_payload_size - 8);
175                }
176            }
177        }
178
179        if (size > 2 && !buf[0] && !buf[1])
180            send_mode_a(s1, &info, buf, len, ebits, len == size);
181        else
182            send_mode_b(s1, &info, &packet_start_state, buf, len, sbits,
183                        ebits, len == size);
184
185        if (ebits) {
186            sbits = 8 - ebits;
187            len--;
188        } else {
189            sbits = 0;
190        }
191        buf  += len;
192        size -= len;
193        ebits = 0;
194    }
195}
196