1 /*
2 * RTP H.263 Depacketizer, RFC 4629
3 * Copyright (c) 2010 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 "rtpdec_formats.h"
24 #include "libavutil/attributes.h"
25 #include "libavutil/intreadwrite.h"
26
ff_h263_handle_packet(AVFormatContext * ctx,PayloadContext * data,AVStream * st,AVPacket * pkt,uint32_t * timestamp,const uint8_t * buf,int len,uint16_t seq,int flags)27 int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,
28 AVStream *st, AVPacket *pkt, uint32_t *timestamp,
29 const uint8_t *buf, int len, uint16_t seq, int flags)
30 {
31 uint8_t *ptr;
32 uint16_t header;
33 int startcode, vrc, picture_header, ret;
34
35 if (len < 2) {
36 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
37 return AVERROR_INVALIDDATA;
38 }
39
40 /* Decode the 16 bit H.263+ payload header, as described in section
41 * 5.1 of RFC 4629. The fields of this header are:
42 * - 5 reserved bits, should be ignored.
43 * - One bit (P, startcode), indicating a picture start, picture segment
44 * start or video sequence end. If set, two zero bytes should be
45 * prepended to the payload.
46 * - One bit (V, vrc), indicating the presence of an 8 bit Video
47 * Redundancy Coding field after this 16 bit header.
48 * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra
49 * picture header, following the VRC field.
50 * - 3 bits (PEBIT), the number of bits to ignore of the last byte
51 * of the extra picture header. (Not used at the moment.)
52 */
53 header = AV_RB16(buf);
54 startcode = (header & 0x0400) >> 9;
55 vrc = header & 0x0200;
56 picture_header = (header & 0x01f8) >> 3;
57 buf += 2;
58 len -= 2;
59
60 if (vrc) {
61 /* Skip VRC header if present, not used at the moment. */
62 buf += 1;
63 len -= 1;
64 }
65 if (picture_header) {
66 /* Skip extra picture header if present, not used at the moment. */
67 buf += picture_header;
68 len -= picture_header;
69 }
70
71 if (len < 0) {
72 av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n");
73 return AVERROR_INVALIDDATA;
74 }
75
76 if ((ret = av_new_packet(pkt, len + startcode)) < 0) {
77 av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
78 return ret;
79 }
80 pkt->stream_index = st->index;
81 ptr = pkt->data;
82
83 if (startcode) {
84 *ptr++ = 0;
85 *ptr++ = 0;
86 }
87 memcpy(ptr, buf, len);
88
89 return 0;
90 }
91
92 const RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = {
93 .enc_name = "H263-1998",
94 .codec_type = AVMEDIA_TYPE_VIDEO,
95 .codec_id = AV_CODEC_ID_H263,
96 .need_parsing = AVSTREAM_PARSE_FULL,
97 .parse_packet = ff_h263_handle_packet,
98 };
99
100 const RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = {
101 .enc_name = "H263-2000",
102 .codec_type = AVMEDIA_TYPE_VIDEO,
103 .codec_id = AV_CODEC_ID_H263,
104 .need_parsing = AVSTREAM_PARSE_FULL,
105 .parse_packet = ff_h263_handle_packet,
106 };
107