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rtpdec_ac3.c
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1 /*
2  * RTP parser for AC3 payload format (RFC 4184)
3  * Copyright (c) 2015 Gilles Chanteperdrix <gch@xenomai.org>
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 "avio_internal.h"
24 #include "rtpdec_formats.h"
25 
26 #define RTP_AC3_PAYLOAD_HEADER_SIZE 2
27 
28 struct PayloadContext {
29  unsigned nr_frames;
30  unsigned last_frame;
31  uint32_t timestamp;
33 };
34 
36 {
38 }
39 
41  AVStream *st, AVPacket *pkt, uint32_t *timestamp,
42  const uint8_t *buf, int len, uint16_t seq,
43  int flags)
44 {
45  unsigned frame_type;
46  unsigned nr_frames;
47  int err;
48 
49  if (len < RTP_AC3_PAYLOAD_HEADER_SIZE + 1) {
50  av_log(ctx, AV_LOG_ERROR, "Invalid %d bytes packet\n", len);
51  return AVERROR_INVALIDDATA;
52  }
53 
54  frame_type = buf[0] & 0x3;
55  nr_frames = buf[1];
58 
59  switch (frame_type) {
60  case 0: /* One or more complete frames */
61  if (!nr_frames) {
62  av_log(ctx, AV_LOG_ERROR, "Invalid AC3 packet data\n");
63  return AVERROR_INVALIDDATA;
64  }
65  if (av_new_packet(pkt, len)) {
66  av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
67  return AVERROR(ENOMEM);
68  }
69 
70  pkt->stream_index = st->index;
71  memcpy(pkt->data, buf, len);
72  return 0;
73 
74  case 1:
75  case 2: /* First fragment */
77 
78  data->last_frame = 1;
79  data->nr_frames = nr_frames;
80  err = avio_open_dyn_buf(&data->fragment);
81  if (err < 0)
82  return err;
83 
84  avio_write(data->fragment, buf, len);
85  data->timestamp = *timestamp;
86  return AVERROR(EAGAIN);
87 
88  case 3: /* Fragment other than first */
89  if (!data->fragment) {
91  "Received packet without a start fragment; dropping.\n");
92  return AVERROR(EAGAIN);
93  }
94  if (nr_frames != data->nr_frames ||
95  data->timestamp != *timestamp) {
97  av_log(ctx, AV_LOG_ERROR, "Invalid packet received\n");
98  return AVERROR_INVALIDDATA;
99  }
100 
101  avio_write(data->fragment, buf, len);
102  data->last_frame++;
103  }
104 
105  if (!(flags & RTP_FLAG_MARKER))
106  return AVERROR(EAGAIN);
107 
108  if (data->last_frame != data->nr_frames) {
109  ffio_free_dyn_buf(&data->fragment);
110  av_log(ctx, AV_LOG_ERROR, "Missed %d packets\n",
111  data->nr_frames - data->last_frame);
112  return AVERROR_INVALIDDATA;
113  }
114 
115  err = ff_rtp_finalize_packet(pkt, &data->fragment, st->index);
116  if (err < 0) {
117  av_log(ctx, AV_LOG_ERROR,
118  "Error occurred when getting fragment buffer.\n");
119  return err;
120  }
121 
122  return 0;
123 }
124 
126  .enc_name = "ac3",
127  .codec_type = AVMEDIA_TYPE_AUDIO,
128  .codec_id = AV_CODEC_ID_AC3,
129  .need_parsing = AVSTREAM_PARSE_FULL,
130  .priv_data_size = sizeof(PayloadContext),
131  .close = ac3_close_context,
133 };