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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 | ||
27 | static av_cold int h263_init(AVFormatContext *ctx, int st_index, | |
28 | PayloadContext *data) | |
29 | { | |
30 | if (st_index < 0) | |
31 | return 0; | |
32 | ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL; | |
33 | return 0; | |
34 | } | |
35 | ||
36 | int ff_h263_handle_packet(AVFormatContext *ctx, PayloadContext *data, | |
37 | AVStream *st, AVPacket *pkt, uint32_t *timestamp, | |
38 | const uint8_t *buf, int len, uint16_t seq, int flags) | |
39 | { | |
40 | uint8_t *ptr; | |
41 | uint16_t header; | |
42 | int startcode, vrc, picture_header; | |
43 | ||
44 | if (len < 2) { | |
45 | av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); | |
46 | return AVERROR_INVALIDDATA; | |
47 | } | |
48 | ||
49 | /* Decode the 16 bit H.263+ payload header, as described in section | |
50 | * 5.1 of RFC 4629. The fields of this header are: | |
51 | * - 5 reserved bits, should be ignored. | |
52 | * - One bit (P, startcode), indicating a picture start, picture segment | |
53 | * start or video sequence end. If set, two zero bytes should be | |
54 | * prepended to the payload. | |
55 | * - One bit (V, vrc), indicating the presence of an 8 bit Video | |
56 | * Redundancy Coding field after this 16 bit header. | |
57 | * - 6 bits (PLEN, picture_header), the length (in bytes) of an extra | |
58 | * picture header, following the VRC field. | |
59 | * - 3 bits (PEBIT), the number of bits to ignore of the last byte | |
60 | * of the extra picture header. (Not used at the moment.) | |
61 | */ | |
62 | header = AV_RB16(buf); | |
63 | startcode = (header & 0x0400) >> 9; | |
64 | vrc = header & 0x0200; | |
65 | picture_header = (header & 0x01f8) >> 3; | |
66 | buf += 2; | |
67 | len -= 2; | |
68 | ||
69 | if (vrc) { | |
70 | /* Skip VRC header if present, not used at the moment. */ | |
71 | buf += 1; | |
72 | len -= 1; | |
73 | } | |
74 | if (picture_header) { | |
75 | /* Skip extra picture header if present, not used at the moment. */ | |
76 | buf += picture_header; | |
77 | len -= picture_header; | |
78 | } | |
79 | ||
80 | if (len < 0) { | |
81 | av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet\n"); | |
82 | return AVERROR_INVALIDDATA; | |
83 | } | |
84 | ||
85 | if (av_new_packet(pkt, len + startcode)) { | |
86 | av_log(ctx, AV_LOG_ERROR, "Out of memory\n"); | |
87 | return AVERROR(ENOMEM); | |
88 | } | |
89 | pkt->stream_index = st->index; | |
90 | ptr = pkt->data; | |
91 | ||
92 | if (startcode) { | |
93 | *ptr++ = 0; | |
94 | *ptr++ = 0; | |
95 | } | |
96 | memcpy(ptr, buf, len); | |
97 | ||
98 | return 0; | |
99 | } | |
100 | ||
101 | RTPDynamicProtocolHandler ff_h263_1998_dynamic_handler = { | |
102 | .enc_name = "H263-1998", | |
103 | .codec_type = AVMEDIA_TYPE_VIDEO, | |
104 | .codec_id = AV_CODEC_ID_H263, | |
105 | .init = h263_init, | |
106 | .parse_packet = ff_h263_handle_packet, | |
107 | }; | |
108 | ||
109 | RTPDynamicProtocolHandler ff_h263_2000_dynamic_handler = { | |
110 | .enc_name = "H263-2000", | |
111 | .codec_type = AVMEDIA_TYPE_VIDEO, | |
112 | .codec_id = AV_CODEC_ID_H263, | |
113 | .init = h263_init, | |
114 | .parse_packet = ff_h263_handle_packet, | |
115 | }; |