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
26static 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};
29static 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
33struct PayloadContext {
34    int octet_align;
35    int crc;
36    int interleaving;
37    int channels;
38};
39
40static PayloadContext *amr_new_context(void)
41{
42    PayloadContext *data = av_mallocz(sizeof(PayloadContext));
43    if(!data) return data;
44    data->channels = 1;
45    return data;
46}
47
48static void amr_free_context(PayloadContext *data)
49{
50    av_free(data);
51}
52
53static int amr_handle_packet(AVFormatContext *ctx,
54                             PayloadContext *data,
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
143static int amr_parse_fmtp(AVStream *stream, PayloadContext *data,
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
166static 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
189RTPDynamicProtocolHandler ff_amr_nb_dynamic_handler = {
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
199RTPDynamicProtocolHandler ff_amr_wb_dynamic_handler = {
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
209