libavformat/rtpdec_ac3.c

   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
  28 struct PayloadContext {
  29     unsigned nr_frames;
  30     unsigned last_frame;
  31     uint32_t timestamp;
  32     AVIOContext *fragment;
  33 };
  34
  35 static void ac3_close_context(PayloadContext *data)
  36 {
  37     ffio_free_dyn_buf(&data->fragment);
  38 }
  39
  40 static 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
 125 const 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 };