/*
  * 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) {
         /* 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
 };