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rtpdec_amr.c
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1 /*
2  * RTP AMR Depacketizer, RFC 3267
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 
23 #include "avformat.h"
24 #include "rtpdec_formats.h"
25 #include "libavutil/avstring.h"
26 
27 static const uint8_t frame_sizes_nb[16] = {
28  12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0
29 };
30 static const uint8_t frame_sizes_wb[16] = {
31  17, 23, 32, 36, 40, 46, 50, 58, 60, 5, 5, 0, 0, 0, 0, 0
32 };
33 
34 struct PayloadContext {
36  int crc;
38  int channels;
39 };
40 
42 {
44  if(!data) return data;
45  data->channels = 1;
46  return data;
47 }
48 
50 {
51  av_free(data);
52 }
53 
55  AVStream *st, AVPacket *pkt, uint32_t *timestamp,
56  const uint8_t *buf, int len, uint16_t seq,
57  int flags)
58 {
59  const uint8_t *frame_sizes = NULL;
60  int frames;
61  int i;
62  const uint8_t *speech_data;
63  uint8_t *ptr;
64 
65  if (st->codec->codec_id == AV_CODEC_ID_AMR_NB) {
66  frame_sizes = frame_sizes_nb;
67  } else if (st->codec->codec_id == AV_CODEC_ID_AMR_WB) {
68  frame_sizes = frame_sizes_wb;
69  } else {
70  av_log(ctx, AV_LOG_ERROR, "Bad codec ID\n");
71  return AVERROR_INVALIDDATA;
72  }
73 
74  if (st->codec->channels != 1) {
75  av_log(ctx, AV_LOG_ERROR, "Only mono AMR is supported\n");
76  return AVERROR_INVALIDDATA;
77  }
79 
80  /* The AMR RTP packet consists of one header byte, followed
81  * by one TOC byte for each AMR frame in the packet, followed
82  * by the speech data for all the AMR frames.
83  *
84  * The header byte contains only a codec mode request, for
85  * requesting what kind of AMR data the sender wants to
86  * receive. Not used at the moment.
87  */
88 
89  /* Count the number of frames in the packet. The highest bit
90  * is set in a TOC byte if there are more frames following.
91  */
92  for (frames = 1; frames < len && (buf[frames] & 0x80); frames++) ;
93 
94  if (1 + frames >= len) {
95  /* We hit the end of the packet while counting frames. */
96  av_log(ctx, AV_LOG_ERROR, "No speech data found\n");
97  return AVERROR_INVALIDDATA;
98  }
99 
100  speech_data = buf + 1 + frames;
101 
102  /* Everything except the codec mode request byte should be output. */
103  if (av_new_packet(pkt, len - 1)) {
104  av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
105  return AVERROR(ENOMEM);
106  }
107  pkt->stream_index = st->index;
108  ptr = pkt->data;
109 
110  for (i = 0; i < frames; i++) {
111  uint8_t toc = buf[1 + i];
112  int frame_size = frame_sizes[(toc >> 3) & 0x0f];
113 
114  if (speech_data + frame_size > buf + len) {
115  /* Too little speech data */
116  av_log(ctx, AV_LOG_WARNING, "Too little speech data in the RTP packet\n");
117  /* Set the unwritten part of the packet to zero. */
118  memset(ptr, 0, pkt->data + pkt->size - ptr);
119  pkt->size = ptr - pkt->data;
120  return 0;
121  }
122 
123  /* Extract the AMR frame mode from the TOC byte */
124  *ptr++ = toc & 0x7C;
125 
126  /* Copy the speech data */
127  memcpy(ptr, speech_data, frame_size);
128  speech_data += frame_size;
129  ptr += frame_size;
130  }
131 
132  if (speech_data < buf + len) {
133  av_log(ctx, AV_LOG_WARNING, "Too much speech data in the RTP packet?\n");
134  /* Set the unwritten part of the packet to zero. */
135  memset(ptr, 0, pkt->data + pkt->size - ptr);
136  pkt->size = ptr - pkt->data;
137  }
138 
139  return 0;
140 }
141 
143  char *attr, char *value)
144 {
145  /* Some AMR SDP configurations contain "octet-align", without
146  * the trailing =1. Therefore, if the value is empty,
147  * interpret it as "1".
148  */
149  if (!strcmp(value, "")) {
150  av_log(NULL, AV_LOG_WARNING, "AMR fmtp attribute %s had "
151  "nonstandard empty value\n", attr);
152  strcpy(value, "1");
153  }
154  if (!strcmp(attr, "octet-align"))
155  data->octet_align = atoi(value);
156  else if (!strcmp(attr, "crc"))
157  data->crc = atoi(value);
158  else if (!strcmp(attr, "interleaving"))
159  data->interleaving = atoi(value);
160  else if (!strcmp(attr, "channels"))
161  data->channels = atoi(value);
162  return 0;
163 }
164 
165 static int amr_parse_sdp_line(AVFormatContext *s, int st_index,
166  PayloadContext *data, const char *line)
167 {
168  const char *p;
169  int ret;
170 
171  if (st_index < 0)
172  return 0;
173 
174  /* Parse an fmtp line this one:
175  * a=fmtp:97 octet-align=1; interleaving=0
176  * That is, a normal fmtp: line followed by semicolon & space
177  * separated key/value pairs.
178  */
179  if (av_strstart(line, "fmtp:", &p)) {
180  ret = ff_parse_fmtp(s->streams[st_index], data, p, amr_parse_fmtp);
181  if (!data->octet_align || data->crc ||
182  data->interleaving || data->channels != 1) {
183  av_log(s, AV_LOG_ERROR, "Unsupported RTP/AMR configuration!\n");
184  return -1;
185  }
186  return ret;
187  }
188  return 0;
189 }
190 
192  .enc_name = "AMR",
193  .codec_type = AVMEDIA_TYPE_AUDIO,
194  .codec_id = AV_CODEC_ID_AMR_NB,
195  .parse_sdp_a_line = amr_parse_sdp_line,
196  .alloc = amr_new_context,
197  .free = amr_free_context,
198  .parse_packet = amr_handle_packet,
199 };
200 
202  .enc_name = "AMR-WB",
203  .codec_type = AVMEDIA_TYPE_AUDIO,
204  .codec_id = AV_CODEC_ID_AMR_WB,
205  .parse_sdp_a_line = amr_parse_sdp_line,
206  .alloc = amr_new_context,
207  .free = amr_free_context,
208  .parse_packet = amr_handle_packet,
209 };