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rtpdec_h263_rfc2190.c
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1 /*
2  * RTP H.263 Depacketizer, RFC 2190
3  * Copyright (c) 2012 Martin Storsjo
4  * Based on the GStreamer H.263 Depayloder:
5  * Copyright 2005 Wim Taymans
6  * Copyright 2007 Edward Hervey
7  * Copyright 2007 Nokia Corporation
8  * Copyright 2007 Collabora Ltd, Philippe Kalaf
9  * Copyright 2010 Mark Nauwelaerts
10  *
11  * This file is part of FFmpeg.
12  *
13  * FFmpeg is free software; you can redistribute it and/or
14  * modify it under the terms of the GNU Lesser General Public
15  * License as published by the Free Software Foundation; either
16  * version 2.1 of the License, or (at your option) any later version.
17  *
18  * FFmpeg is distributed in the hope that it will be useful,
19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21  * Lesser General Public License for more details.
22  *
23  * You should have received a copy of the GNU Lesser General Public
24  * License along with FFmpeg; if not, write to the Free Software
25  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26  */
27 
28 #include "avformat.h"
29 #include "avio_internal.h"
30 #include "rtpdec_formats.h"
31 #include "libavutil/attributes.h"
32 #include "libavutil/intreadwrite.h"
33 #include "libavcodec/get_bits.h"
34 
35 struct PayloadContext {
38  int endbyte_bits;
39  uint32_t timestamp;
40  int newformat;
41 };
42 
44 {
45  ffio_free_dyn_buf(&data->buf);
46 }
47 
49  AVStream *st, AVPacket *pkt, uint32_t *timestamp,
50  const uint8_t *buf, int len, uint16_t seq,
51  int flags)
52 {
53  /* Corresponding to header fields in the RFC */
54  int f, p, i, sbit, ebit, src, r;
55  int header_size, ret;
56 
57  if (data->newformat)
58  return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf, len,
59  seq, flags);
60 
61  if (data->buf && data->timestamp != *timestamp) {
62  /* Dropping old buffered, unfinished data */
63  ffio_free_dyn_buf(&data->buf);
64  data->endbyte_bits = 0;
65  }
66 
67  if (len < 4) {
68  av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet: %d\n", len);
69  return AVERROR_INVALIDDATA;
70  }
71 
72  f = buf[0] & 0x80;
73  p = buf[0] & 0x40;
74  if (!f) {
75  /* Mode A */
76  header_size = 4;
77  i = buf[1] & 0x10;
78  r = ((buf[1] & 0x01) << 3) | ((buf[2] & 0xe0) >> 5);
79  } else if (!p) {
80  /* Mode B */
81  header_size = 8;
82  if (len < header_size) {
83  av_log(ctx, AV_LOG_ERROR,
84  "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
85  len, header_size);
86  return AVERROR_INVALIDDATA;
87  }
88  r = buf[3] & 0x03;
89  i = buf[4] & 0x80;
90  } else {
91  /* Mode C */
92  header_size = 12;
93  if (len < header_size) {
94  av_log(ctx, AV_LOG_ERROR,
95  "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
96  len, header_size);
97  return AVERROR_INVALIDDATA;
98  }
99  r = buf[3] & 0x03;
100  i = buf[4] & 0x80;
101  }
102  sbit = (buf[0] >> 3) & 0x7;
103  ebit = buf[0] & 0x7;
104  src = (buf[1] & 0xe0) >> 5;
105  if (!(buf[0] & 0xf8)) { /* Reserved bits in RFC 2429/4629 are zero */
106  if ((src == 0 || src >= 6) && r) {
107  /* Invalid src for this format, and bits that should be zero
108  * according to RFC 2190 aren't zero. */
109  av_log(ctx, AV_LOG_WARNING,
110  "Interpreting H263 RTP data as RFC 2429/4629 even though "
111  "signalled with a static payload type.\n");
112  data->newformat = 1;
113  return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf,
114  len, seq, flags);
115  }
116  }
117 
118  buf += header_size;
119  len -= header_size;
120 
121  if (!data->buf) {
122  /* Check the picture start code, only start buffering a new frame
123  * if this is correct */
124  if (len > 4 && AV_RB32(buf) >> 10 == 0x20) {
125  ret = avio_open_dyn_buf(&data->buf);
126  if (ret < 0)
127  return ret;
128  data->timestamp = *timestamp;
129  } else {
130  /* Frame not started yet, skipping */
131  return AVERROR(EAGAIN);
132  }
133  }
134 
135  if (data->endbyte_bits || sbit) {
136  if (data->endbyte_bits == sbit) {
137  data->endbyte |= buf[0] & (0xff >> sbit);
138  data->endbyte_bits = 0;
139  buf++;
140  len--;
141  avio_w8(data->buf, data->endbyte);
142  } else {
143  /* Start/end skip bits not matching - missed packets? */
144  GetBitContext gb;
145  init_get_bits(&gb, buf, len*8 - ebit);
146  skip_bits(&gb, sbit);
147  if (data->endbyte_bits) {
148  data->endbyte |= get_bits(&gb, 8 - data->endbyte_bits);
149  avio_w8(data->buf, data->endbyte);
150  }
151  while (get_bits_left(&gb) >= 8)
152  avio_w8(data->buf, get_bits(&gb, 8));
153  data->endbyte_bits = get_bits_left(&gb);
154  if (data->endbyte_bits)
155  data->endbyte = get_bits(&gb, data->endbyte_bits) <<
156  (8 - data->endbyte_bits);
157  ebit = 0;
158  len = 0;
159  }
160  }
161  if (ebit) {
162  if (len > 0)
163  avio_write(data->buf, buf, len - 1);
164  data->endbyte_bits = 8 - ebit;
165  data->endbyte = buf[len - 1] & (0xff << ebit);
166  } else {
167  avio_write(data->buf, buf, len);
168  }
169 
170  if (!(flags & RTP_FLAG_MARKER))
171  return AVERROR(EAGAIN);
172 
173  if (data->endbyte_bits)
174  avio_w8(data->buf, data->endbyte);
175  data->endbyte_bits = 0;
176 
177  ret = ff_rtp_finalize_packet(pkt, &data->buf, st->index);
178  if (ret < 0)
179  return ret;
180  if (!i)
181  pkt->flags |= AV_PKT_FLAG_KEY;
182 
183  return 0;
184 }
185 
188  .codec_id = AV_CODEC_ID_H263,
189  .need_parsing = AVSTREAM_PARSE_FULL,
190  .parse_packet = h263_handle_packet,
191  .priv_data_size = sizeof(PayloadContext),
192  .close = h263_close_context,
193  .static_payload_id = 34,
194 };