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rtpdec_vp8.c
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1 /*
2  * RTP VP8 Depacketizer
3  * Copyright (c) 2010 Josh Allmann
4  * Copyright (c) 2012 Martin Storsjo
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * @brief RTP support for the VP8 payload
26  * @author Josh Allmann <joshua.allmann@gmail.com>
27  * @see http://tools.ietf.org/html/draft-ietf-payload-vp8-05
28  */
29 
30 #include "libavcodec/bytestream.h"
31 
32 #include "rtpdec_formats.h"
33 
34 struct PayloadContext {
36  uint32_t timestamp;
38  /* If sequence_ok is set, we keep returning data (even if we might have
39  * lost some data, but we haven't lost any too critical data that would
40  * cause the decoder to desynchronize and output random garbage).
41  */
44  uint16_t prev_seq;
47  /* If sequence_dirty is set, we have lost some data (critical or
48  * non-critical) and decoding will have some sort of artefacts, and
49  * we thus should request a new keyframe.
50  */
53 };
54 
56 {
57  uint8_t *tmp;
58  if (!vp8->data)
59  return;
60  avio_close_dyn_buf(vp8->data, &tmp);
61  av_free(tmp);
62  vp8->data = NULL;
63 }
64 
66  const char *msg)
67 {
68  vp8->sequence_ok = 0;
69  av_log(ctx, AV_LOG_WARNING, "%s", msg);
70  vp8_free_buffer(vp8);
71  return AVERROR(EAGAIN);
72 }
73 
75  AVStream *st, AVPacket *pkt, uint32_t *timestamp,
76  const uint8_t *buf, int len, uint16_t seq,
77  int flags)
78 {
79  int start_partition, end_packet;
80  int extended_bits, part_id;
81  int pictureid_present = 0, tl0picidx_present = 0, tid_present = 0,
82  keyidx_present = 0;
83  int pictureid = -1, pictureid_mask = 0;
84  int returned_old_frame = 0;
85  uint32_t old_timestamp = 0;
86 
87  if (!buf) {
88  if (vp8->data) {
89  int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
90  if (ret < 0)
91  return ret;
92  *timestamp = vp8->timestamp;
93  if (vp8->sequence_dirty)
94  pkt->flags |= AV_PKT_FLAG_CORRUPT;
95  return 0;
96  }
97  return AVERROR(EAGAIN);
98  }
99 
100  if (len < 1)
101  return AVERROR_INVALIDDATA;
102 
103  extended_bits = buf[0] & 0x80;
104  start_partition = buf[0] & 0x10;
105  part_id = buf[0] & 0x0f;
106  end_packet = flags & RTP_FLAG_MARKER;
107  buf++;
108  len--;
109  if (extended_bits) {
110  if (len < 1)
111  return AVERROR_INVALIDDATA;
112  pictureid_present = buf[0] & 0x80;
113  tl0picidx_present = buf[0] & 0x40;
114  tid_present = buf[0] & 0x20;
115  keyidx_present = buf[0] & 0x10;
116  buf++;
117  len--;
118  }
119  if (pictureid_present) {
120  if (len < 1)
121  return AVERROR_INVALIDDATA;
122  if (buf[0] & 0x80) {
123  if (len < 2)
124  return AVERROR_INVALIDDATA;
125  pictureid = AV_RB16(buf) & 0x7fff;
126  pictureid_mask = 0x7fff;
127  buf += 2;
128  len -= 2;
129  } else {
130  pictureid = buf[0] & 0x7f;
131  pictureid_mask = 0x7f;
132  buf++;
133  len--;
134  }
135  }
136  if (tl0picidx_present) {
137  // Ignoring temporal level zero index
138  buf++;
139  len--;
140  }
141  if (tid_present || keyidx_present) {
142  // Ignoring temporal layer index, layer sync bit and keyframe index
143  buf++;
144  len--;
145  }
146  if (len < 1)
147  return AVERROR_INVALIDDATA;
148 
149  if (start_partition && part_id == 0 && len >= 3) {
150  int res;
151  int non_key = buf[0] & 0x01;
152  if (!non_key) {
153  vp8_free_buffer(vp8);
154  // Keyframe, decoding ok again
155  vp8->sequence_ok = 1;
156  vp8->sequence_dirty = 0;
157  vp8->got_keyframe = 1;
158  } else {
159  int can_continue = vp8->data && !vp8->is_keyframe &&
160  avio_tell(vp8->data) >= vp8->first_part_size;
161  if (!vp8->sequence_ok)
162  return AVERROR(EAGAIN);
163  if (!vp8->got_keyframe)
164  return vp8_broken_sequence(ctx, vp8, "Keyframe missing\n");
165  if (pictureid >= 0) {
166  if (pictureid != ((vp8->prev_pictureid + 1) & pictureid_mask)) {
167  return vp8_broken_sequence(ctx, vp8,
168  "Missed a picture, sequence broken\n");
169  } else {
170  if (vp8->data && !can_continue)
171  return vp8_broken_sequence(ctx, vp8,
172  "Missed a picture, sequence broken\n");
173  }
174  } else {
175  uint16_t expected_seq = vp8->prev_seq + 1;
176  int16_t diff = seq - expected_seq;
177  if (vp8->data) {
178  // No picture id, so we can't know if missed packets
179  // contained any new frames. If diff == 0, we did get
180  // later packets from the same frame (matching timestamp),
181  // so we know we didn't miss any frame. If diff == 1 and
182  // we still have data (not flushed by the end of frame
183  // marker), the single missed packet must have been part
184  // of the same frame.
185  if ((diff == 0 || diff == 1) && can_continue) {
186  // Proceed with what we have
187  } else {
188  return vp8_broken_sequence(ctx, vp8,
189  "Missed too much, sequence broken\n");
190  }
191  } else {
192  if (diff != 0)
193  return vp8_broken_sequence(ctx, vp8,
194  "Missed unknown data, sequence broken\n");
195  }
196  }
197  if (vp8->data) {
198  vp8->sequence_dirty = 1;
199  if (avio_tell(vp8->data) >= vp8->first_part_size) {
200  int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
201  if (ret < 0)
202  return ret;
203  pkt->flags |= AV_PKT_FLAG_CORRUPT;
204  returned_old_frame = 1;
205  old_timestamp = vp8->timestamp;
206  } else {
207  // Shouldn't happen
208  vp8_free_buffer(vp8);
209  }
210  }
211  }
212  vp8->first_part_size = (AV_RL16(&buf[1]) << 3 | buf[0] >> 5) + 3;
213  if ((res = avio_open_dyn_buf(&vp8->data)) < 0)
214  return res;
215  vp8->timestamp = *timestamp;
216  vp8->broken_frame = 0;
217  vp8->prev_pictureid = pictureid;
218  vp8->is_keyframe = !non_key;
219  } else {
220  uint16_t expected_seq = vp8->prev_seq + 1;
221 
222  if (!vp8->sequence_ok)
223  return AVERROR(EAGAIN);
224 
225  if (vp8->timestamp != *timestamp) {
226  // Missed the start of the new frame, sequence broken
227  return vp8_broken_sequence(ctx, vp8,
228  "Received no start marker; dropping frame\n");
229  }
230 
231  if (seq != expected_seq) {
232  if (vp8->is_keyframe) {
233  return vp8_broken_sequence(ctx, vp8,
234  "Missed part of a keyframe, sequence broken\n");
235  } else if (vp8->data && avio_tell(vp8->data) >= vp8->first_part_size) {
236  vp8->broken_frame = 1;
237  vp8->sequence_dirty = 1;
238  } else {
239  return vp8_broken_sequence(ctx, vp8,
240  "Missed part of the first partition, sequence broken\n");
241  }
242  }
243  }
244 
245  if (!vp8->data)
246  return vp8_broken_sequence(ctx, vp8, "Received no start marker\n");
247 
248  vp8->prev_seq = seq;
249  if (!vp8->broken_frame)
250  avio_write(vp8->data, buf, len);
251 
252  if (returned_old_frame) {
253  *timestamp = old_timestamp;
254  return end_packet ? 1 : 0;
255  }
256 
257  if (end_packet) {
258  int ret;
259  ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
260  if (ret < 0)
261  return ret;
262  if (vp8->sequence_dirty)
263  pkt->flags |= AV_PKT_FLAG_CORRUPT;
264  return 0;
265  }
266 
267  return AVERROR(EAGAIN);
268 }
269 
271 {
272  PayloadContext *vp8 = av_mallocz(sizeof(PayloadContext));
273  if (!vp8)
274  return NULL;
275  vp8->sequence_ok = 1;
276  return vp8;
277 }
278 
280 {
281  vp8_free_buffer(vp8);
282  av_free(vp8);
283 }
284 
286 {
287  return vp8->sequence_dirty || !vp8->sequence_ok;
288 }
289 
291  .enc_name = "VP8",
292  .codec_type = AVMEDIA_TYPE_VIDEO,
293  .codec_id = AV_CODEC_ID_VP8,
294  .alloc = vp8_new_context,
295  .free = vp8_free_context,
296  .parse_packet = vp8_handle_packet,
297  .need_keyframe = vp8_need_keyframe,
298 };