text: /*
   * RTP VP8 Depacketizer
   * Copyright (c) 2010 Josh Allmann
   * Copyright (c) 2012 Martin Storsjo
   *
   * 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
   */
  
  /**
   * @file
   * @brief RTP support for the VP8 payload
   * @author Josh Allmann <joshua.allmann@gmail.com>
   * @see http://tools.ietf.org/html/draft-ietf-payload-vp8-05
   */
  
  #include "libavcodec/bytestream.h"
  
  #include "avio_internal.h"
  #include "rtpdec_formats.h"
  
  struct PayloadContext {
      AVIOContext *data;
      uint32_t     timestamp;
      int          is_keyframe;
      /* If sequence_ok is set, we keep returning data (even if we might have
       * lost some data, but we haven't lost any too critical data that would
       * cause the decoder to desynchronize and output random garbage).
       */
      int          sequence_ok;
      int          first_part_size;
      uint16_t     prev_seq;
      int          prev_pictureid;
      int          broken_frame;
      /* If sequence_dirty is set, we have lost some data (critical or
       * non-critical) and decoding will have some sort of artefacts, and
       * we thus should request a new keyframe.
       */
      int          sequence_dirty;
      int          got_keyframe;
  };
  
  static int vp8_broken_sequence(AVFormatContext *ctx, PayloadContext *vp8,
                                 const char *msg)
  {
      vp8->sequence_ok = 0;
      av_log(ctx, AV_LOG_WARNING, "%s", msg);
      ffio_free_dyn_buf(&vp8->data);
      return AVERROR(EAGAIN);
  }
  
  static int vp8_handle_packet(AVFormatContext *ctx, PayloadContext *vp8,
                               AVStream *st, AVPacket *pkt, uint32_t *timestamp,
                               const uint8_t *buf, int len, uint16_t seq,
                               int flags)
  {
      int start_partition, end_packet;
      int extended_bits, part_id;
      int pictureid_present = 0, tl0picidx_present = 0, tid_present = 0,
          keyidx_present = 0;
      int pictureid = -1, pictureid_mask = 0;
      int returned_old_frame = 0;
      uint32_t old_timestamp = 0;
  
      if (!buf) {
          if (vp8->data) {
              int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
              if (ret < 0)
                  return ret;
              *timestamp = vp8->timestamp;
              if (vp8->sequence_dirty)
                  pkt->flags |= AV_PKT_FLAG_CORRUPT;
              return 0;
          }
          return AVERROR(EAGAIN);
      }
  
      if (len < 1)
          return AVERROR_INVALIDDATA;
  
      extended_bits   = buf[0] & 0x80;
      start_partition = buf[0] & 0x10;
      part_id         = buf[0] & 0x0f;
      end_packet      = flags & RTP_FLAG_MARKER;
      buf++;
      len--;
      if (extended_bits) {
          if (len < 1)
              return AVERROR_INVALIDDATA;
          pictureid_present = buf[0] & 0x80;
          tl0picidx_present = buf[0] & 0x40;
          tid_present       = buf[0] & 0x20;
          keyidx_present    = buf[0] & 0x10;
          buf++;
          len--;
      }
      if (pictureid_present) {
          if (len < 1)
              return AVERROR_INVALIDDATA;
          if (buf[0] & 0x80) {
              if (len < 2)
                  return AVERROR_INVALIDDATA;
              pictureid = AV_RB16(buf) & 0x7fff;
              pictureid_mask = 0x7fff;
              buf += 2;
              len -= 2;
          } else {
              pictureid = buf[0] & 0x7f;
              pictureid_mask = 0x7f;
              buf++;
              len--;
          }
      }
      if (tl0picidx_present) {
          // Ignoring temporal level zero index
          buf++;
          len--;
      }
      if (tid_present || keyidx_present) {
          // Ignoring temporal layer index, layer sync bit and keyframe index
          buf++;
          len--;
      }
      if (len < 1)
          return AVERROR_INVALIDDATA;
  
      if (start_partition && part_id == 0 && len >= 3) {
          int res;
          int non_key = buf[0] & 0x01;
          if (!non_key) {
              ffio_free_dyn_buf(&vp8->data);
              // Keyframe, decoding ok again
              vp8->sequence_ok = 1;
              vp8->sequence_dirty = 0;
              vp8->got_keyframe = 1;
          } else {
              int can_continue = vp8->data && !vp8->is_keyframe &&
                                 avio_tell(vp8->data) >= vp8->first_part_size;
              if (!vp8->sequence_ok)
                  return AVERROR(EAGAIN);
              if (!vp8->got_keyframe)
                  return vp8_broken_sequence(ctx, vp8, "Keyframe missing\n");
              if (pictureid >= 0) {
                  if (pictureid != ((vp8->prev_pictureid + 1) & pictureid_mask)) {
                      return vp8_broken_sequence(ctx, vp8,
                                                 "Missed a picture, sequence broken\n");
                  } else {
                      if (vp8->data && !can_continue)
                          return vp8_broken_sequence(ctx, vp8,
                                                     "Missed a picture, sequence broken\n");
                  }
              } else {
                  uint16_t expected_seq = vp8->prev_seq + 1;
                  int16_t diff = seq - expected_seq;
                  if (vp8->data) {
                      // No picture id, so we can't know if missed packets
                      // contained any new frames. If diff == 0, we did get
                      // later packets from the same frame (matching timestamp),
                      // so we know we didn't miss any frame. If diff == 1 and
                      // we still have data (not flushed by the end of frame
                      // marker), the single missed packet must have been part
                      // of the same frame.
                      if ((diff == 0 || diff == 1) && can_continue) {
                          // Proceed with what we have
                      } else {
                          return vp8_broken_sequence(ctx, vp8,
                                                     "Missed too much, sequence broken\n");
                      }
                  } else {
                      if (diff != 0)
                          return vp8_broken_sequence(ctx, vp8,
                                                     "Missed unknown data, sequence broken\n");
                  }
              }
              if (vp8->data) {
                  vp8->sequence_dirty = 1;
                  if (avio_tell(vp8->data) >= vp8->first_part_size) {
                      int ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
                      if (ret < 0)
                          return ret;
                      pkt->flags |= AV_PKT_FLAG_CORRUPT;
                      returned_old_frame = 1;
                      old_timestamp = vp8->timestamp;
                  } else {
                      // Shouldn't happen
                      ffio_free_dyn_buf(&vp8->data);
                  }
              }
          }
          vp8->first_part_size = (AV_RL16(&buf[1]) << 3 | buf[0] >> 5) + 3;
          if ((res = avio_open_dyn_buf(&vp8->data)) < 0)
              return res;
          vp8->timestamp = *timestamp;
          vp8->broken_frame = 0;
          vp8->prev_pictureid = pictureid;
          vp8->is_keyframe = !non_key;
      } else {
          uint16_t expected_seq = vp8->prev_seq + 1;
  
          if (!vp8->sequence_ok)
              return AVERROR(EAGAIN);
  
          if (vp8->timestamp != *timestamp) {
              // Missed the start of the new frame, sequence broken
              return vp8_broken_sequence(ctx, vp8,
                                         "Received no start marker; dropping frame\n");
          }
  
          if (seq != expected_seq) {
              if (vp8->is_keyframe) {
                  return vp8_broken_sequence(ctx, vp8,
                                             "Missed part of a keyframe, sequence broken\n");
              } else if (vp8->data && avio_tell(vp8->data) >= vp8->first_part_size) {
                  vp8->broken_frame = 1;
                  vp8->sequence_dirty = 1;
              } else {
                  return vp8_broken_sequence(ctx, vp8,
                                             "Missed part of the first partition, sequence broken\n");
              }
          }
      }
  
      if (!vp8->data)
          return vp8_broken_sequence(ctx, vp8, "Received no start marker\n");
  
      vp8->prev_seq = seq;
      if (!vp8->broken_frame)
          avio_write(vp8->data, buf, len);
  
      if (returned_old_frame) {
          *timestamp = old_timestamp;
          return end_packet ? 1 : 0;
      }
  
      if (end_packet) {
          int ret;
          ret = ff_rtp_finalize_packet(pkt, &vp8->data, st->index);
          if (ret < 0)
              return ret;
          if (vp8->sequence_dirty)
              pkt->flags |= AV_PKT_FLAG_CORRUPT;
          if (vp8->is_keyframe)
              pkt->flags |= AV_PKT_FLAG_KEY;
          return 0;
      }
  
      return AVERROR(EAGAIN);
  }
  
  static av_cold int vp8_init(AVFormatContext *s, int st_index, PayloadContext *vp8)
  {
      vp8->sequence_ok = 1;
      return 0;
  }
  
  static void vp8_close_context(PayloadContext *vp8)
  {
      ffio_free_dyn_buf(&vp8->data);
  }
  
  static int vp8_need_keyframe(PayloadContext *vp8)
  {
      return vp8->sequence_dirty || !vp8->sequence_ok;
  }
  
  RTPDynamicProtocolHandler ff_vp8_dynamic_handler = {
      .enc_name       = "VP8",
      .codec_type     = AVMEDIA_TYPE_VIDEO,
      .codec_id       = AV_CODEC_ID_VP8,
      .priv_data_size = sizeof(PayloadContext),
      .init           = vp8_init,
      .close          = vp8_close_context,
      .parse_packet   = vp8_handle_packet,
      .need_keyframe  = vp8_need_keyframe,
  };
  