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
28struct PayloadContext {
29    unsigned nr_frames;
30    unsigned last_frame;
31    uint32_t timestamp;
32    AVIOContext *fragment;
33};
34
35static void ac3_close_context(PayloadContext *data)
36{
37    ffio_free_dyn_buf(&data->fragment);
38}
39
40static int ac3_handle_packet(AVFormatContext *ctx, PayloadContext *data,
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];
56    buf += RTP_AC3_PAYLOAD_HEADER_SIZE;
57    len -= RTP_AC3_PAYLOAD_HEADER_SIZE;
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 ((err = av_new_packet(pkt, len)) < 0) {
66            av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
67            return err;
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 */
76        ffio_free_dyn_buf(&data->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) {
90            av_log(ctx, AV_LOG_WARNING,
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) {
96            ffio_free_dyn_buf(&data->fragment);
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
125const RTPDynamicProtocolHandler ff_ac3_dynamic_handler = {
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,
132    .parse_packet       = ac3_handle_packet,
133};
134