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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 Libav.
12  *
13  * Libav 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  * Libav 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 Libav; 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 "rtpdec_formats.h"
30 #include "libavutil/attributes.h"
31 #include "libavutil/intreadwrite.h"
32 #include "libavcodec/get_bits.h"
33 
34 struct PayloadContext {
38  uint32_t timestamp;
39  int newformat;
40 };
41 
43 {
44  return av_mallocz(sizeof(PayloadContext));
45 }
46 
48 {
49  if (!data)
50  return;
51  if (data->buf) {
52  uint8_t *p;
53  avio_close_dyn_buf(data->buf, &p);
54  av_free(p);
55  }
56  av_free(data);
57 }
58 
59 static av_cold int h263_init(AVFormatContext *ctx, int st_index, PayloadContext *data)
60 {
61  if (st_index < 0)
62  return 0;
63  ctx->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL;
64  return 0;
65 }
66 
68  AVStream *st, AVPacket *pkt, uint32_t *timestamp,
69  const uint8_t *buf, int len, uint16_t seq,
70  int flags)
71 {
72  /* Corresponding to header fields in the RFC */
73  int f, p, i, sbit, ebit, src, r;
74  int header_size, ret;
75 
76  if (data->newformat)
77  return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf, len,
78  seq, flags);
79 
80  if (data->buf && data->timestamp != *timestamp) {
81  /* Dropping old buffered, unfinished data */
82  uint8_t *p;
83  avio_close_dyn_buf(data->buf, &p);
84  av_free(p);
85  data->buf = NULL;
86  }
87 
88  if (len < 4) {
89  av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet: %d\n", len);
90  return AVERROR_INVALIDDATA;
91  }
92 
93  f = buf[0] & 0x80;
94  p = buf[0] & 0x40;
95  if (!f) {
96  /* Mode A */
97  header_size = 4;
98  i = buf[1] & 0x10;
99  r = ((buf[1] & 0x01) << 3) | ((buf[2] & 0xe0) >> 5);
100  } else if (!p) {
101  /* Mode B */
102  header_size = 8;
103  if (len < header_size) {
104  av_log(ctx, AV_LOG_ERROR,
105  "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
106  len, header_size);
107  return AVERROR_INVALIDDATA;
108  }
109  r = buf[3] & 0x03;
110  i = buf[4] & 0x80;
111  } else {
112  /* Mode C */
113  header_size = 12;
114  if (len < header_size) {
115  av_log(ctx, AV_LOG_ERROR,
116  "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
117  len, header_size);
118  return AVERROR_INVALIDDATA;
119  }
120  r = buf[3] & 0x03;
121  i = buf[4] & 0x80;
122  }
123  sbit = (buf[0] >> 3) & 0x7;
124  ebit = buf[0] & 0x7;
125  src = (buf[1] & 0xe0) >> 5;
126  if (!(buf[0] & 0xf8)) { /* Reserved bits in RFC 2429/4629 are zero */
127  if ((src == 0 || src >= 6) && r) {
128  /* Invalid src for this format, and bits that should be zero
129  * according to RFC 2190 aren't zero. */
130  av_log(ctx, AV_LOG_WARNING,
131  "Interpreting H263 RTP data as RFC 2429/4629 even though "
132  "signalled with a static payload type.\n");
133  data->newformat = 1;
134  return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf,
135  len, seq, flags);
136  }
137  }
138 
139  buf += header_size;
140  len -= header_size;
141 
142  if (!data->buf) {
143  /* Check the picture start code, only start buffering a new frame
144  * if this is correct */
145  if (len > 4 && AV_RB32(buf) >> 10 == 0x20) {
146  ret = avio_open_dyn_buf(&data->buf);
147  if (ret < 0)
148  return ret;
149  data->timestamp = *timestamp;
150  } else {
151  /* Frame not started yet, skipping */
152  return AVERROR(EAGAIN);
153  }
154  }
155 
156  if (data->endbyte_bits || sbit) {
157  if (data->endbyte_bits == sbit) {
158  data->endbyte |= buf[0] & (0xff >> sbit);
159  data->endbyte_bits = 0;
160  buf++;
161  len--;
162  avio_w8(data->buf, data->endbyte);
163  } else {
164  /* Start/end skip bits not matching - missed packets? */
165  GetBitContext gb;
166  init_get_bits(&gb, buf, len*8 - ebit);
167  skip_bits(&gb, sbit);
168  if (data->endbyte_bits) {
169  data->endbyte |= get_bits(&gb, 8 - data->endbyte_bits);
170  avio_w8(data->buf, data->endbyte);
171  }
172  while (get_bits_left(&gb) >= 8)
173  avio_w8(data->buf, get_bits(&gb, 8));
174  data->endbyte_bits = get_bits_left(&gb);
175  if (data->endbyte_bits)
176  data->endbyte = get_bits(&gb, data->endbyte_bits) <<
177  (8 - data->endbyte_bits);
178  ebit = 0;
179  len = 0;
180  }
181  }
182  if (ebit) {
183  if (len > 0)
184  avio_write(data->buf, buf, len - 1);
185  data->endbyte_bits = 8 - ebit;
186  data->endbyte = buf[len - 1] & (0xff << ebit);
187  } else {
188  avio_write(data->buf, buf, len);
189  }
190 
191  if (!(flags & RTP_FLAG_MARKER))
192  return AVERROR(EAGAIN);
193 
194  if (data->endbyte_bits)
195  avio_w8(data->buf, data->endbyte);
196  data->endbyte_bits = 0;
197 
198  ret = ff_rtp_finalize_packet(pkt, &data->buf, st->index);
199  if (ret < 0)
200  return ret;
201  if (!i)
202  pkt->flags |= AV_PKT_FLAG_KEY;
203 
204  return 0;
205 }
206 
209  .codec_id = AV_CODEC_ID_H263,
210  .init = h263_init,
211  .parse_packet = h263_handle_packet,
212  .alloc = h263_new_context,
213  .free = h263_free_context,
214  .static_payload_id = 34,
215 };