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
22#include "libavutil/channel_layout.h"
23#include "avformat.h"
24#include "rtpdec_formats.h"
25#include "libavutil/avstring.h"
26
27static 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};
30static 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
34struct PayloadContext {
35    int octet_align;
36    int crc;
37    int interleaving;
38    int channels;
39};
40
41static av_cold int amr_init(AVFormatContext *s, int st_index, PayloadContext *data)
42{
43    data->channels = 1;
44    return 0;
45}
46
47static int amr_handle_packet(AVFormatContext *ctx, PayloadContext *data,
48                             AVStream *st, AVPacket *pkt, uint32_t *timestamp,
49                             const uint8_t *buf, int len, uint16_t seq,
50                             int flags)
51{
52    const uint8_t *frame_sizes = NULL;
53    int frames;
54    int i, ret;
55    const uint8_t *speech_data;
56    uint8_t *ptr;
57
58    if (st->codecpar->codec_id == AV_CODEC_ID_AMR_NB) {
59        frame_sizes = frame_sizes_nb;
60    } else if (st->codecpar->codec_id == AV_CODEC_ID_AMR_WB) {
61        frame_sizes = frame_sizes_wb;
62    } else {
63        av_log(ctx, AV_LOG_ERROR, "Bad codec ID\n");
64        return AVERROR_INVALIDDATA;
65    }
66
67    if (st->codecpar->ch_layout.nb_channels != 1) {
68        av_log(ctx, AV_LOG_ERROR, "Only mono AMR is supported\n");
69        return AVERROR_INVALIDDATA;
70    }
71    av_channel_layout_default(&st->codecpar->ch_layout, 1);
72
73    /* The AMR RTP packet consists of one header byte, followed
74     * by one TOC byte for each AMR frame in the packet, followed
75     * by the speech data for all the AMR frames.
76     *
77     * The header byte contains only a codec mode request, for
78     * requesting what kind of AMR data the sender wants to
79     * receive. Not used at the moment.
80     */
81
82    /* Count the number of frames in the packet. The highest bit
83     * is set in a TOC byte if there are more frames following.
84     */
85    for (frames = 1; frames < len && (buf[frames] & 0x80); frames++) ;
86
87    if (1 + frames >= len) {
88        /* We hit the end of the packet while counting frames. */
89        av_log(ctx, AV_LOG_ERROR, "No speech data found\n");
90        return AVERROR_INVALIDDATA;
91    }
92
93    speech_data = buf + 1 + frames;
94
95    /* Everything except the codec mode request byte should be output. */
96    if ((ret = av_new_packet(pkt, len - 1)) < 0) {
97        av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
98        return ret;
99    }
100    pkt->stream_index = st->index;
101    ptr = pkt->data;
102
103    for (i = 0; i < frames; i++) {
104        uint8_t toc = buf[1 + i];
105        int frame_size = frame_sizes[(toc >> 3) & 0x0f];
106
107        if (speech_data + frame_size > buf + len) {
108            /* Too little speech data */
109            av_log(ctx, AV_LOG_WARNING, "Too little speech data in the RTP packet\n");
110            /* Set the unwritten part of the packet to zero. */
111            memset(ptr, 0, pkt->data + pkt->size - ptr);
112            pkt->size = ptr - pkt->data;
113            return 0;
114        }
115
116        /* Extract the AMR frame mode from the TOC byte */
117        *ptr++ = toc & 0x7C;
118
119        /* Copy the speech data */
120        memcpy(ptr, speech_data, frame_size);
121        speech_data += frame_size;
122        ptr += frame_size;
123    }
124
125    if (speech_data < buf + len) {
126        av_log(ctx, AV_LOG_WARNING, "Too much speech data in the RTP packet?\n");
127        /* Set the unwritten part of the packet to zero. */
128        memset(ptr, 0, pkt->data + pkt->size - ptr);
129        pkt->size = ptr - pkt->data;
130    }
131
132    return 0;
133}
134
135static int amr_parse_fmtp(AVFormatContext *s,
136                          AVStream *stream, PayloadContext *data,
137                          const char *attr, const char *value)
138{
139    /* Some AMR SDP configurations contain "octet-align", without
140     * the trailing =1. Therefore, if the value is empty,
141     * interpret it as "1".
142     */
143    if (!strcmp(value, "")) {
144        av_log(s, AV_LOG_WARNING, "AMR fmtp attribute %s had "
145                                  "nonstandard empty value\n", attr);
146        value = "1";
147    }
148    if (!strcmp(attr, "octet-align"))
149        data->octet_align = atoi(value);
150    else if (!strcmp(attr, "crc"))
151        data->crc = atoi(value);
152    else if (!strcmp(attr, "interleaving"))
153        data->interleaving = atoi(value);
154    else if (!strcmp(attr, "channels"))
155        data->channels = atoi(value);
156    return 0;
157}
158
159static int amr_parse_sdp_line(AVFormatContext *s, int st_index,
160                              PayloadContext *data, const char *line)
161{
162    const char *p;
163    int ret;
164
165    if (st_index < 0)
166        return 0;
167
168    /* Parse an fmtp line this one:
169     * a=fmtp:97 octet-align=1; interleaving=0
170     * That is, a normal fmtp: line followed by semicolon & space
171     * separated key/value pairs.
172     */
173    if (av_strstart(line, "fmtp:", &p)) {
174        ret = ff_parse_fmtp(s, s->streams[st_index], data, p, amr_parse_fmtp);
175        if (!data->octet_align || data->crc ||
176            data->interleaving || data->channels != 1) {
177            av_log(s, AV_LOG_ERROR, "Unsupported RTP/AMR configuration!\n");
178            return -1;
179        }
180        return ret;
181    }
182    return 0;
183}
184
185const RTPDynamicProtocolHandler ff_amr_nb_dynamic_handler = {
186    .enc_name         = "AMR",
187    .codec_type       = AVMEDIA_TYPE_AUDIO,
188    .codec_id         = AV_CODEC_ID_AMR_NB,
189    .priv_data_size   = sizeof(PayloadContext),
190    .init             = amr_init,
191    .parse_sdp_a_line = amr_parse_sdp_line,
192    .parse_packet     = amr_handle_packet,
193};
194
195const RTPDynamicProtocolHandler ff_amr_wb_dynamic_handler = {
196    .enc_name         = "AMR-WB",
197    .codec_type       = AVMEDIA_TYPE_AUDIO,
198    .codec_id         = AV_CODEC_ID_AMR_WB,
199    .priv_data_size   = sizeof(PayloadContext),
200    .init             = amr_init,
201    .parse_sdp_a_line = amr_parse_sdp_line,
202    .parse_packet     = amr_handle_packet,
203};
204