text: /*
   * RTP parser for VP9 payload format (draft version 0) - experimental
   * Copyright (c) 2015 Thomas Volkert <thomas@homer-conferencing.com>
   *
   * 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 "libavutil/intreadwrite.h"
  
  #include "avio_internal.h"
  #include "rtpdec_formats.h"
  
  #define RTP_VP9_DESC_REQUIRED_SIZE 1
  
  struct PayloadContext {
      AVIOContext *buf;
      uint32_t     timestamp;
  };
  
  static av_cold int vp9_init(AVFormatContext *ctx, int st_index,
                              PayloadContext *data)
  {
      av_log(ctx, AV_LOG_WARNING,
             "RTP/VP9 support is still experimental\n");
  
      return 0;
  }
  
  static int vp9_handle_packet(AVFormatContext *ctx, PayloadContext *rtp_vp9_ctx,
                               AVStream *st, AVPacket *pkt, uint32_t *timestamp,
                               const uint8_t *buf, int len, uint16_t seq,
                               int flags)
  {
      int has_pic_id, has_layer_idc, has_ref_idc, has_ss_data, has_su_data;
      av_unused int pic_id = 0, non_key_frame = 0;
      av_unused int layer_temporal = -1, layer_spatial = -1, layer_quality = -1;
      int ref_fields = 0, has_ref_field_ext_pic_id = 0;
      int first_fragment, last_fragment;
      int rtp_m;
      int res = 0;
  
      /* drop data of previous packets in case of non-continuous (lossy) packet stream */
      if (rtp_vp9_ctx->buf && rtp_vp9_ctx->timestamp != *timestamp)
          ffio_free_dyn_buf(&rtp_vp9_ctx->buf);
  
      /* sanity check for size of input packet: 1 byte payload at least */
      if (len < RTP_VP9_DESC_REQUIRED_SIZE + 1) {
          av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet, got %d bytes\n", len);
          return AVERROR_INVALIDDATA;
      }
  
      /*
       *     decode the required VP9 payload descriptor according to section 4.2 of the spec.:
       *
       *      0 1 2 3 4 5 6 7
       *     +-+-+-+-+-+-+-+-+
       *     |I|L|F|B|E|V|U|-| (REQUIRED)
       *     +-+-+-+-+-+-+-+-+
       *
       *     I: PictureID present
       *     L: Layer indices present
       *     F: Reference indices present
       *     B: Start of VP9 frame
       *     E: End of picture
       *     V: Scalability Structure (SS) present
       *     U: Scalability Structure Update (SU) present
       */
      has_pic_id     = !!(buf[0] & 0x80);
      has_layer_idc  = !!(buf[0] & 0x40);
      has_ref_idc    = !!(buf[0] & 0x20);
      first_fragment = !!(buf[0] & 0x10);
      last_fragment  = !!(buf[0] & 0x08);
      has_ss_data    = !!(buf[0] & 0x04);
      has_su_data    = !!(buf[0] & 0x02);
  
      rtp_m = !!(flags & RTP_FLAG_MARKER);
  
      /* sanity check for markers: B should always be equal to the RTP M marker */
      if (last_fragment != rtp_m) {
          av_log(ctx, AV_LOG_ERROR, "Invalid combination of B and M marker (%d != %d)\n", last_fragment, rtp_m);
          return AVERROR_INVALIDDATA;
      }
  
      /* pass the extensions field */
      buf += RTP_VP9_DESC_REQUIRED_SIZE;
      len -= RTP_VP9_DESC_REQUIRED_SIZE;
  
      /*
       *         decode the 1-byte/2-byte picture ID:
       *
       *          0 1 2 3 4 5 6 7
       *         +-+-+-+-+-+-+-+-+
       *   I:    |M|PICTURE ID   | (RECOMMENDED)
       *         +-+-+-+-+-+-+-+-+
       *   M:    | EXTENDED PID  | (RECOMMENDED)
       *         +-+-+-+-+-+-+-+-+
       *
       *   M: The most significant bit of the first octet is an extension flag.
       *   PictureID:  8 or 16 bits including the M bit.
       */
      if (has_pic_id) {
          if (len < 1) {
              av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
              return AVERROR_INVALIDDATA;
          }
  
          /* check for 1-byte or 2-byte picture index */
          if (buf[0] & 0x80) {
              if (len < 2) {
                  av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
                  return AVERROR_INVALIDDATA;
              }
              pic_id = AV_RB16(buf) & 0x7fff;
              buf += 2;
              len -= 2;
          } else {
              pic_id = buf[0] & 0x7f;
              buf++;
              len--;
          }
      }
  
      /*
       *         decode layer indices
       *
       *          0 1 2 3 4 5 6 7
       *         +-+-+-+-+-+-+-+-+
       *   L:    | T | S | Q | R | (CONDITIONALLY RECOMMENDED)
       *         +-+-+-+-+-+-+-+-+
       *
       *   T, S and Q are 2-bit indices for temporal, spatial, and quality layers.
       *   If "F" is set in the initial octet, R is 2 bits representing the number
       *   of reference fields this frame refers to.
       */
      if (has_layer_idc) {
          if (len < 1) {
              av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
              return AVERROR_INVALIDDATA;
          }
          layer_temporal = buf[0] & 0xC0;
          layer_spatial  = buf[0] & 0x30;
          layer_quality  = buf[0] & 0x0C;
          if (has_ref_idc) {
              ref_fields = buf[0] & 0x03;
              if (ref_fields)
                  non_key_frame = 1;
          }
          buf++;
          len--;
      }
  
      /*
       *         decode the reference fields
       *
       *          0 1 2 3 4 5 6 7
       *         +-+-+-+-+-+-+-+-+              -\
       *   F:    | PID |X| RS| RQ| (OPTIONAL)    .
       *         +-+-+-+-+-+-+-+-+               . - R times
       *   X:    | EXTENDED PID  | (OPTIONAL)    .
       *         +-+-+-+-+-+-+-+-+              -/
       *
       *   PID:  The relative Picture ID referred to by this frame.
       *   RS and RQ:  The spatial and quality layer IDs.
       *   X: 1 if this layer index has an extended relative Picture ID.
       */
      if (has_ref_idc) {
          while (ref_fields) {
              if (len < 1) {
                  av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
                  return AVERROR_INVALIDDATA;
              }
  
              has_ref_field_ext_pic_id = buf[0] & 0x10;
  
              /* pass ref. field */
              if (has_ref_field_ext_pic_id) {
                  if (len < 2) {
                      av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
                      return AVERROR_INVALIDDATA;
                  }
  
                  /* ignore ref. data */
  
                  buf += 2;
                  len -= 2;
              } else {
  
                  /* ignore ref. data */
  
                  buf++;
                  len--;
              }
              ref_fields--;
          }
      }
  
      /*
       *         decode the scalability structure (SS)
       *
       *          0 1 2 3 4 5 6 7
       *         +-+-+-+-+-+-+-+-+
       *   V:    | PATTERN LENGTH|
       *         +-+-+-+-+-+-+-+-+                           -\
       *         | T | S | Q | R | (OPTIONAL)                 .
       *         +-+-+-+-+-+-+-+-+              -\            .
       *         | PID |X| RS| RQ| (OPTIONAL)    .            . - PAT. LEN. times
       *         +-+-+-+-+-+-+-+-+               . - R times  .
       *   X:    | EXTENDED PID  | (OPTIONAL)    .            .
       *         +-+-+-+-+-+-+-+-+              -/           -/
       *
       *   PID:  The relative Picture ID referred to by this frame.
       *   RS and RQ:  The spatial and quality layer IDs.
       *   X: 1 if this layer index has an extended relative Picture ID.
       */
      if (has_ss_data) {
          avpriv_report_missing_feature(ctx, "VP9 scalability structure data");
          return AVERROR(ENOSYS);
      }
  
      /*
       * decode the scalability update structure (SU)
       *
       *  spec. is tbd
       */
      if (has_su_data) {
          avpriv_report_missing_feature(ctx, "VP9 scalability update structure data");
          return AVERROR(ENOSYS);
      }
  
      /*
       * decode the VP9 payload header
       *
       *  spec. is tbd
       */
      //XXX: implement when specified
  
      /* sanity check: 1 byte payload as minimum */
      if (len < 1) {
          av_log(ctx, AV_LOG_ERROR, "Too short RTP/VP9 packet\n");
          return AVERROR_INVALIDDATA;
      }
  
      /* start frame buffering with new dynamic buffer */
      if (!rtp_vp9_ctx->buf) {
          /* sanity check: a new frame should have started */
          if (first_fragment) {
              res = avio_open_dyn_buf(&rtp_vp9_ctx->buf);
              if (res < 0)
                  return res;
              /* update the timestamp in the frame packet with the one from the RTP packet */
              rtp_vp9_ctx->timestamp = *timestamp;
          } else {
              /* frame not started yet, need more packets */
              return AVERROR(EAGAIN);
          }
      }
  
      /* write the fragment to the dyn. buffer */
      avio_write(rtp_vp9_ctx->buf, buf, len);
  
      /* do we need more fragments? */
      if (!last_fragment)
          return AVERROR(EAGAIN);
  
      /* close frame buffering and create resulting A/V packet */
      res = ff_rtp_finalize_packet(pkt, &rtp_vp9_ctx->buf, st->index);
      if (res < 0)
          return res;
  
      return 0;
  }
  
  RTPDynamicProtocolHandler ff_vp9_dynamic_handler = {
      .enc_name         = "VP9",
      .codec_type       = AVMEDIA_TYPE_VIDEO,
      .codec_id         = AV_CODEC_ID_VP9,
      .priv_data_size   = sizeof(PayloadContext),
      .init             = vp9_init,
      .parse_packet     = vp9_handle_packet
  };
  