/*
  * RTP parser for AC3 payload format (RFC 4184)
  * Copyright (c) 2015 Gilles Chanteperdrix <gch@xenomai.org>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "avformat.h"

 #include "avio_internal.h"

 #include "rtpdec_formats.h"
 
 #define RTP_AC3_PAYLOAD_HEADER_SIZE 2
 
 struct PayloadContext {
     unsigned nr_frames;
     unsigned last_frame;
     uint32_t timestamp;
     AVIOContext *fragment;
 };
 

 static void ac3_close_context(PayloadContext *data)

 {

     ffio_free_dyn_buf(&data->fragment);

 }
 
 static int ac3_handle_packet(AVFormatContext *ctx, PayloadContext *data,

                              AVStream *st, AVPacket *pkt, uint32_t *timestamp,
                              const uint8_t *buf, int len, uint16_t seq,
                              int flags)

 {
     unsigned frame_type;
     unsigned nr_frames;
     int err;
 
     if (len < RTP_AC3_PAYLOAD_HEADER_SIZE + 1) {
         av_log(ctx, AV_LOG_ERROR, "Invalid %d bytes packet\n", len);
         return AVERROR_INVALIDDATA;
     }
 
     frame_type = buf[0] & 0x3;
     nr_frames = buf[1];
     buf += RTP_AC3_PAYLOAD_HEADER_SIZE;
     len -= RTP_AC3_PAYLOAD_HEADER_SIZE;
 
     switch (frame_type) {
     case 0: /* One or more complete frames */
         if (!nr_frames) {
             av_log(ctx, AV_LOG_ERROR, "Invalid AC3 packet data\n");
             return AVERROR_INVALIDDATA;
         }
         if (av_new_packet(pkt, len)) {
             av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
             return AVERROR(ENOMEM);
         }
 
         pkt->stream_index = st->index;
         memcpy(pkt->data, buf, len);
         return 0;
 
     case 1:
     case 2: /* First fragment */

         ffio_free_dyn_buf(&data->fragment);

 
         data->last_frame = 1;
         data->nr_frames = nr_frames;
         err = avio_open_dyn_buf(&data->fragment);
         if (err < 0)
             return err;
 
         avio_write(data->fragment, buf, len);
         data->timestamp = *timestamp;
         return AVERROR(EAGAIN);
 
     case 3: /* Fragment other than first */
         if (!data->fragment) {
             av_log(ctx, AV_LOG_WARNING,
                    "Received packet without a start fragment; dropping.\n");
             return AVERROR(EAGAIN);
         }
         if (nr_frames != data->nr_frames ||
             data->timestamp != *timestamp) {

             ffio_free_dyn_buf(&data->fragment);

             av_log(ctx, AV_LOG_ERROR, "Invalid packet received\n");
             return AVERROR_INVALIDDATA;
         }
 
         avio_write(data->fragment, buf, len);
         data->last_frame++;
     }
 
     if (!(flags & RTP_FLAG_MARKER))
         return AVERROR(EAGAIN);
 
     if (data->last_frame != data->nr_frames) {

         ffio_free_dyn_buf(&data->fragment);

         av_log(ctx, AV_LOG_ERROR, "Missed %d packets\n",
                data->nr_frames - data->last_frame);
         return AVERROR_INVALIDDATA;
     }
 
     err = ff_rtp_finalize_packet(pkt, &data->fragment, st->index);
     if (err < 0) {
         av_log(ctx, AV_LOG_ERROR,

                "Error occurred when getting fragment buffer.\n");

         return err;
     }
 
     return 0;
 }
 
 RTPDynamicProtocolHandler ff_ac3_dynamic_handler = {
     .enc_name           = "ac3",
     .codec_type         = AVMEDIA_TYPE_AUDIO,
     .codec_id           = AV_CODEC_ID_AC3,

     .need_parsing       = AVSTREAM_PARSE_FULL,

     .priv_data_size     = sizeof(PayloadContext),

     .close              = ac3_close_context,

     .parse_packet       = ac3_handle_packet,
 };