/*
  * RTP H.263 Depacketizer, RFC 2190
  * Copyright (c) 2012 Martin Storsjo
  * Based on the GStreamer H.263 Depayloder:
  * Copyright 2005 Wim Taymans
  * Copyright 2007 Edward Hervey
  * Copyright 2007 Nokia Corporation
  * Copyright 2007 Collabora Ltd, Philippe Kalaf
  * Copyright 2010 Mark Nauwelaerts
  *

  * 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"

 #include "libavutil/attributes.h"

 #include "libavutil/intreadwrite.h"
 #include "libavcodec/get_bits.h"
 
 struct PayloadContext {
     AVIOContext *buf;
     uint8_t      endbyte;
     int          endbyte_bits;
     uint32_t     timestamp;

     int          newformat;

 };
 

 static void h263_close_context(PayloadContext *data)

 {

     ffio_free_dyn_buf(&data->buf);

 }
 
 static int h263_handle_packet(AVFormatContext *ctx, PayloadContext *data,
                               AVStream *st, AVPacket *pkt, uint32_t *timestamp,

                               const uint8_t *buf, int len, uint16_t seq,
                               int flags)

 {

     /* Corresponding to header fields in the RFC */
     int f, p, i, sbit, ebit, src, r;

     int header_size, ret;

     if (data->newformat)
         return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf, len,

                                      seq, flags);

     if (data->buf && data->timestamp != *timestamp) {
         /* Dropping old buffered, unfinished data */

         ffio_free_dyn_buf(&data->buf);

         data->endbyte_bits = 0;

     }
 
     if (len < 4) {
         av_log(ctx, AV_LOG_ERROR, "Too short H.263 RTP packet: %d\n", len);
         return AVERROR_INVALIDDATA;
     }
 
     f = buf[0] & 0x80;
     p = buf[0] & 0x40;
     if (!f) {
         /* Mode A */
         header_size = 4;
         i = buf[1] & 0x10;

         r = ((buf[1] & 0x01) << 3) | ((buf[2] & 0xe0) >> 5);

     } else if (!p) {
         /* Mode B */
         header_size = 8;
         if (len < header_size) {
             av_log(ctx, AV_LOG_ERROR,
                    "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
                    len, header_size);
             return AVERROR_INVALIDDATA;
         }

         r = buf[3] & 0x03;

         i = buf[4] & 0x80;
     } else {
         /* Mode C */
         header_size = 12;
         if (len < header_size) {
             av_log(ctx, AV_LOG_ERROR,
                    "Too short H.263 RTP packet: %d bytes, %d header bytes\n",
                    len, header_size);
             return AVERROR_INVALIDDATA;
         }

         r = buf[3] & 0x03;

         i = buf[4] & 0x80;
     }
     sbit = (buf[0] >> 3) & 0x7;
     ebit =  buf[0]       & 0x7;

     src  = (buf[1] & 0xe0) >> 5;
     if (!(buf[0] & 0xf8)) { /* Reserved bits in RFC 2429/4629 are zero */
         if ((src == 0 || src >= 6) && r) {
             /* Invalid src for this format, and bits that should be zero
              * according to RFC 2190 aren't zero. */
             av_log(ctx, AV_LOG_WARNING,
                    "Interpreting H263 RTP data as RFC 2429/4629 even though "
                    "signalled with a static payload type.\n");
             data->newformat = 1;
             return ff_h263_handle_packet(ctx, data, st, pkt, timestamp, buf,

                                          len, seq, flags);

         }
     }

 
     buf += header_size;
     len -= header_size;
 
     if (!data->buf) {
         /* Check the picture start code, only start buffering a new frame
          * if this is correct */

         if (len > 4 && AV_RB32(buf) >> 10 == 0x20) {

             ret = avio_open_dyn_buf(&data->buf);

             if (ret < 0)
                 return ret;
             data->timestamp = *timestamp;
         } else {
             /* Frame not started yet, skipping */
             return AVERROR(EAGAIN);
         }
     }
 
     if (data->endbyte_bits || sbit) {
         if (data->endbyte_bits == sbit) {
             data->endbyte |= buf[0] & (0xff >> sbit);
             data->endbyte_bits = 0;
             buf++;
             len--;
             avio_w8(data->buf, data->endbyte);
         } else {
             /* Start/end skip bits not matching - missed packets? */
             GetBitContext gb;
             init_get_bits(&gb, buf, len*8 - ebit);
             skip_bits(&gb, sbit);
             if (data->endbyte_bits) {
                 data->endbyte |= get_bits(&gb, 8 - data->endbyte_bits);
                 avio_w8(data->buf, data->endbyte);
             }
             while (get_bits_left(&gb) >= 8)
                 avio_w8(data->buf, get_bits(&gb, 8));
             data->endbyte_bits = get_bits_left(&gb);
             if (data->endbyte_bits)
                 data->endbyte = get_bits(&gb, data->endbyte_bits) <<
                                 (8 - data->endbyte_bits);
             ebit = 0;
             len = 0;
         }
     }
     if (ebit) {
         if (len > 0)
             avio_write(data->buf, buf, len - 1);
         data->endbyte_bits = 8 - ebit;
         data->endbyte = buf[len - 1] & (0xff << ebit);
     } else {
         avio_write(data->buf, buf, len);
     }
 
     if (!(flags & RTP_FLAG_MARKER))
         return AVERROR(EAGAIN);
 
     if (data->endbyte_bits)
         avio_w8(data->buf, data->endbyte);
     data->endbyte_bits = 0;
 

     ret = ff_rtp_finalize_packet(pkt, &data->buf, st->index);
     if (ret < 0)
         return ret;

     if (!i)
         pkt->flags   |= AV_PKT_FLAG_KEY;
 
     return 0;
 }
 
 RTPDynamicProtocolHandler ff_h263_rfc2190_dynamic_handler = {
     .codec_type        = AVMEDIA_TYPE_VIDEO,

     .codec_id          = AV_CODEC_ID_H263,

     .need_parsing      = AVSTREAM_PARSE_FULL,

     .parse_packet      = h263_handle_packet,

     .priv_data_size    = sizeof(PayloadContext),

     .close             = h263_close_context,

     .static_payload_id = 34,
 };