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 Libav.
6  *
7  * Libav 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  * Libav 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 Libav; 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 "rtpdec_formats.h"
24 #include "libavutil/avstring.h"
25 
26 static const uint8_t frame_sizes_nb[16] = {
27  12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0
28 };
29 static const uint8_t frame_sizes_wb[16] = {
30  17, 23, 32, 36, 40, 46, 50, 58, 60, 5, 5, 0, 0, 0, 0, 0
31 };
32 
33 struct PayloadContext {
35  int crc;
37  int channels;
38 };
39 
41 {
43  if(!data) return data;
44  data->channels = 1;
45  return data;
46 }
47 
49 {
50  av_free(data);
51 }
52 
55  AVStream *st,
56  AVPacket * pkt,
57  uint32_t * timestamp,
58  const uint8_t * buf,
59  int len, int flags)
60 {
61  const uint8_t *frame_sizes = NULL;
62  int frames;
63  int i;
64  const uint8_t *speech_data;
65  uint8_t *ptr;
66 
67  if (st->codec->codec_id == CODEC_ID_AMR_NB) {
68  frame_sizes = frame_sizes_nb;
69  } else if (st->codec->codec_id == CODEC_ID_AMR_WB) {
70  frame_sizes = frame_sizes_wb;
71  } else {
72  av_log(ctx, AV_LOG_ERROR, "Bad codec ID\n");
73  return AVERROR_INVALIDDATA;
74  }
75 
76  if (st->codec->channels != 1) {
77  av_log(ctx, AV_LOG_ERROR, "Only mono AMR is supported\n");
78  return AVERROR_INVALIDDATA;
79  }
80 
81  /* The AMR RTP packet consists of one header byte, followed
82  * by one TOC byte for each AMR frame in the packet, followed
83  * by the speech data for all the AMR frames.
84  *
85  * The header byte contains only a codec mode request, for
86  * requesting what kind of AMR data the sender wants to
87  * receive. Not used at the moment.
88  */
89 
90  /* Count the number of frames in the packet. The highest bit
91  * is set in a TOC byte if there are more frames following.
92  */
93  for (frames = 1; frames < len && (buf[frames] & 0x80); frames++) ;
94 
95  if (1 + frames >= len) {
96  /* We hit the end of the packet while counting frames. */
97  av_log(ctx, AV_LOG_ERROR, "No speech data found\n");
98  return AVERROR_INVALIDDATA;
99  }
100 
101  speech_data = buf + 1 + frames;
102 
103  /* Everything except the codec mode request byte should be output. */
104  if (av_new_packet(pkt, len - 1)) {
105  av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
106  return AVERROR(ENOMEM);
107  }
108  pkt->stream_index = st->index;
109  ptr = pkt->data;
110 
111  for (i = 0; i < frames; i++) {
112  uint8_t toc = buf[1 + i];
113  int frame_size = frame_sizes[(toc >> 3) & 0x0f];
114 
115  if (speech_data + frame_size > buf + len) {
116  /* Too little speech data */
117  av_log(ctx, AV_LOG_WARNING, "Too little speech data in the RTP packet\n");
118  /* Set the unwritten part of the packet to zero. */
119  memset(ptr, 0, pkt->data + pkt->size - ptr);
120  pkt->size = ptr - pkt->data;
121  return 0;
122  }
123 
124  /* Extract the AMR frame mode from the TOC byte */
125  *ptr++ = toc & 0x7C;
126 
127  /* Copy the speech data */
128  memcpy(ptr, speech_data, frame_size);
129  speech_data += frame_size;
130  ptr += frame_size;
131  }
132 
133  if (speech_data < buf + len) {
134  av_log(ctx, AV_LOG_WARNING, "Too much speech data in the RTP packet?\n");
135  /* Set the unwritten part of the packet to zero. */
136  memset(ptr, 0, pkt->data + pkt->size - ptr);
137  pkt->size = ptr - pkt->data;
138  }
139 
140  return 0;
141 }
142 
144  char *attr, char *value)
145 {
146  /* Some AMR SDP configurations contain "octet-align", without
147  * the trailing =1. Therefore, if the value is empty,
148  * interpret it as "1".
149  */
150  if (!strcmp(value, "")) {
151  av_log(NULL, AV_LOG_WARNING, "AMR fmtp attribute %s had "
152  "nonstandard empty value\n", attr);
153  strcpy(value, "1");
154  }
155  if (!strcmp(attr, "octet-align"))
156  data->octet_align = atoi(value);
157  else if (!strcmp(attr, "crc"))
158  data->crc = atoi(value);
159  else if (!strcmp(attr, "interleaving"))
160  data->interleaving = atoi(value);
161  else if (!strcmp(attr, "channels"))
162  data->channels = atoi(value);
163  return 0;
164 }
165 
166 static int amr_parse_sdp_line(AVFormatContext *s, int st_index,
167  PayloadContext *data, const char *line)
168 {
169  const char *p;
170  int ret;
171 
172  /* Parse an fmtp line this one:
173  * a=fmtp:97 octet-align=1; interleaving=0
174  * That is, a normal fmtp: line followed by semicolon & space
175  * separated key/value pairs.
176  */
177  if (av_strstart(line, "fmtp:", &p)) {
178  ret = ff_parse_fmtp(s->streams[st_index], data, p, amr_parse_fmtp);
179  if (!data->octet_align || data->crc ||
180  data->interleaving || data->channels != 1) {
181  av_log(s, AV_LOG_ERROR, "Unsupported RTP/AMR configuration!\n");
182  return -1;
183  }
184  return ret;
185  }
186  return 0;
187 }
188 
190  .enc_name = "AMR",
191  .codec_type = AVMEDIA_TYPE_AUDIO,
192  .codec_id = CODEC_ID_AMR_NB,
193  .parse_sdp_a_line = amr_parse_sdp_line,
194  .alloc = amr_new_context,
195  .free = amr_free_context,
196  .parse_packet = amr_handle_packet,
197 };
198 
200  .enc_name = "AMR-WB",
201  .codec_type = AVMEDIA_TYPE_AUDIO,
202  .codec_id = CODEC_ID_AMR_WB,
203  .parse_sdp_a_line = amr_parse_sdp_line,
204  .alloc = amr_new_context,
205  .free = amr_free_context,
206  .parse_packet = amr_handle_packet,
207 };
208