/*
  * RTP input format

  * Copyright (c) 2002 Fabrice Bellard

  *
  * 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/mathematics.h"

 #include "libavutil/avstring.h"

 #include "libavutil/time.h"

 #include "libavcodec/get_bits.h"

 #include "avformat.h"
 #include "network.h"

 #include "srtp.h"

 #include "url.h"

 #include "rtpdec.h"

 #include "rtpdec_formats.h"

 #define MIN_FEEDBACK_INTERVAL 200000 /* 200 ms in us */
 

 static RTPDynamicProtocolHandler gsm_dynamic_handler = {
     .enc_name   = "GSM",
     .codec_type = AVMEDIA_TYPE_AUDIO,
     .codec_id   = AV_CODEC_ID_GSM,
 };
 

 static RTPDynamicProtocolHandler realmedia_mp3_dynamic_handler = {

     .enc_name   = "X-MP3-draft-00",
     .codec_type = AVMEDIA_TYPE_AUDIO,
     .codec_id   = AV_CODEC_ID_MP3ADU,

 };
 

 static RTPDynamicProtocolHandler speex_dynamic_handler = {

     .enc_name   = "speex",
     .codec_type = AVMEDIA_TYPE_AUDIO,
     .codec_id   = AV_CODEC_ID_SPEEX,

 };
 

 static RTPDynamicProtocolHandler opus_dynamic_handler = {

     .enc_name   = "opus",
     .codec_type = AVMEDIA_TYPE_AUDIO,
     .codec_id   = AV_CODEC_ID_OPUS,

 };
 

 static RTPDynamicProtocolHandler *rtp_first_dynamic_payload_handler = NULL;

 void ff_register_dynamic_payload_handler(RTPDynamicProtocolHandler *handler)

 {

     handler->next = rtp_first_dynamic_payload_handler;
     rtp_first_dynamic_payload_handler = handler;

 }
 

 void ff_register_rtp_dynamic_payload_handlers(void)

 {

     ff_register_dynamic_payload_handler(&ff_amr_nb_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_amr_wb_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_g726_16_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_g726_24_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_g726_32_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_g726_40_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_h263_1998_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_h263_2000_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_h263_rfc2190_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_h264_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_ilbc_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_jpeg_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_mp4a_latm_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_mp4v_es_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_mpeg_audio_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_mpeg_video_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_mpeg4_generic_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_mpegts_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_ms_rtp_asf_pfa_handler);

     ff_register_dynamic_payload_handler(&ff_ms_rtp_asf_pfv_handler);

     ff_register_dynamic_payload_handler(&ff_qcelp_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_qdm2_dynamic_handler);

     ff_register_dynamic_payload_handler(&ff_qt_rtp_aud_handler);
     ff_register_dynamic_payload_handler(&ff_qt_rtp_vid_handler);
     ff_register_dynamic_payload_handler(&ff_quicktime_rtp_aud_handler);
     ff_register_dynamic_payload_handler(&ff_quicktime_rtp_vid_handler);

     ff_register_dynamic_payload_handler(&ff_svq3_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_theora_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_vorbis_dynamic_handler);
     ff_register_dynamic_payload_handler(&ff_vp8_dynamic_handler);

     ff_register_dynamic_payload_handler(&gsm_dynamic_handler);

     ff_register_dynamic_payload_handler(&opus_dynamic_handler);
     ff_register_dynamic_payload_handler(&realmedia_mp3_dynamic_handler);
     ff_register_dynamic_payload_handler(&speex_dynamic_handler);

 }
 

 RTPDynamicProtocolHandler *ff_rtp_handler_find_by_name(const char *name,

                                                        enum AVMediaType codec_type)

 {
     RTPDynamicProtocolHandler *handler;

     for (handler = rtp_first_dynamic_payload_handler;

          handler; handler = handler->next)

         if (!av_strcasecmp(name, handler->enc_name) &&

             codec_type == handler->codec_type)
             return handler;
     return NULL;
 }
 
 RTPDynamicProtocolHandler *ff_rtp_handler_find_by_id(int id,

                                                      enum AVMediaType codec_type)

 {
     RTPDynamicProtocolHandler *handler;

     for (handler = rtp_first_dynamic_payload_handler;

          handler; handler = handler->next)
         if (handler->static_payload_id && handler->static_payload_id == id &&
             codec_type == handler->codec_type)
             return handler;
     return NULL;
 }
 

 static int rtcp_parse_packet(RTPDemuxContext *s, const unsigned char *buf,
                              int len)

 {

     int payload_len;

     while (len >= 4) {
         payload_len = FFMIN(len, (AV_RB16(buf + 2) + 1) * 4);
 

         switch (buf[1]) {
         case RTCP_SR:

             if (payload_len < 20) {

                 av_log(NULL, AV_LOG_ERROR,
                        "Invalid length for RTCP SR packet\n");

                 return AVERROR_INVALIDDATA;
             }
 

             s->last_rtcp_reception_time = av_gettime();

             s->last_rtcp_ntp_time  = AV_RB64(buf + 8);

             s->last_rtcp_timestamp = AV_RB32(buf + 16);

             if (s->first_rtcp_ntp_time == AV_NOPTS_VALUE) {
                 s->first_rtcp_ntp_time = s->last_rtcp_ntp_time;
                 if (!s->base_timestamp)
                     s->base_timestamp = s->last_rtcp_timestamp;
                 s->rtcp_ts_offset = s->last_rtcp_timestamp - s->base_timestamp;
             }

 
             break;

         case RTCP_BYE:
             return -RTCP_BYE;

         }

 
         buf += payload_len;
         len -= payload_len;

     }

     return -1;

 }
 

 #define RTP_SEQ_MOD (1 << 16)

 static void rtp_init_statistics(RTPStatistics *s, uint16_t base_sequence)

 {
     memset(s, 0, sizeof(RTPStatistics));

     s->max_seq   = base_sequence;
     s->probation = 1;

 }
 

 /*

  * Called whenever there is a large jump in sequence numbers,
  * or when they get out of probation...
  */

 static void rtp_init_sequence(RTPStatistics *s, uint16_t seq)
 {

     s->max_seq        = seq;
     s->cycles         = 0;
     s->base_seq       = seq - 1;
     s->bad_seq        = RTP_SEQ_MOD + 1;
     s->received       = 0;
     s->expected_prior = 0;
     s->received_prior = 0;
     s->jitter         = 0;
     s->transit        = 0;

 }
 

 /* Returns 1 if we should handle this packet. */

 static int rtp_valid_packet_in_sequence(RTPStatistics *s, uint16_t seq)
 {

     uint16_t udelta = seq - s->max_seq;
     const int MAX_DROPOUT    = 3000;
     const int MAX_MISORDER   = 100;

     const int MIN_SEQUENTIAL = 2;
 

     /* source not valid until MIN_SEQUENTIAL packets with sequence
      * seq. numbers have been received */

     if (s->probation) {
         if (seq == s->max_seq + 1) {

             s->probation--;

             s->max_seq = seq;
             if (s->probation == 0) {

                 rtp_init_sequence(s, seq);
                 s->received++;
                 return 1;
             }
         } else {

             s->probation = MIN_SEQUENTIAL - 1;

             s->max_seq   = seq;

         }
     } else if (udelta < MAX_DROPOUT) {
         // in order, with permissible gap

         if (seq < s->max_seq) {
             // sequence number wrapped; count another 64k cycles

             s->cycles += RTP_SEQ_MOD;
         }

         s->max_seq = seq;

     } else if (udelta <= RTP_SEQ_MOD - MAX_MISORDER) {
         // sequence made a large jump...

         if (seq == s->bad_seq) {

             /* two sequential packets -- assume that the other side
              * restarted without telling us; just resync. */

             rtp_init_sequence(s, seq);
         } else {

             s->bad_seq = (seq + 1) & (RTP_SEQ_MOD - 1);

             return 0;
         }
     } else {
         // duplicate or reordered packet...
     }
     s->received++;
     return 1;
 }
 

 static void rtcp_update_jitter(RTPStatistics *s, uint32_t sent_timestamp,
                                uint32_t arrival_timestamp)
 {
     // Most of this is pretty straight from RFC 3550 appendix A.8
     uint32_t transit = arrival_timestamp - sent_timestamp;
     uint32_t prev_transit = s->transit;
     int32_t d = transit - prev_transit;
     // Doing the FFABS() call directly on the "transit - prev_transit"
     // expression doesn't work, since it's an unsigned expression. Doing the
     // transit calculation in unsigned is desired though, since it most
     // probably will need to wrap around.
     d = FFABS(d);
     s->transit = transit;
     if (!prev_transit)
         return;
     s->jitter += d - (int32_t) ((s->jitter + 8) >> 4);
 }
 

 int ff_rtp_check_and_send_back_rr(RTPDemuxContext *s, URLContext *fd,
                                   AVIOContext *avio, int count)

 {

     AVIOContext *pb;

     uint8_t *buf;
     int len;
     int rtcp_bytes;

     RTPStatistics *stats = &s->statistics;

     uint32_t lost;
     uint32_t extended_max;
     uint32_t expected_interval;
     uint32_t received_interval;

     int32_t  lost_interval;

     uint32_t expected;
     uint32_t fraction;
 

     if ((!fd && !avio) || (count < 1))

         return -1;
 
     /* TODO: I think this is way too often; RFC 1889 has algorithm for this */

     /* XXX: MPEG pts hardcoded. RTCP send every 0.5 seconds */

     s->octet_count += count;
     rtcp_bytes = ((s->octet_count - s->last_octet_count) * RTCP_TX_RATIO_NUM) /
         RTCP_TX_RATIO_DEN;
     rtcp_bytes /= 50; // mmu_man: that's enough for me... VLC sends much less btw !?
     if (rtcp_bytes < 28)
         return -1;
     s->last_octet_count = s->octet_count;
 

     if (!fd)
         pb = avio;
     else if (avio_open_dyn_buf(&pb) < 0)

         return -1;
 
     // Receiver Report

     avio_w8(pb, (RTP_VERSION << 6) + 1); /* 1 report block */
     avio_w8(pb, RTCP_RR);
     avio_wb16(pb, 7); /* length in words - 1 */

     // our own SSRC: we use the server's SSRC + 1 to avoid conflicts

     avio_wb32(pb, s->ssrc + 1);
     avio_wb32(pb, s->ssrc); // server SSRC

     // some placeholders we should really fill...
     // RFC 1889/p64

     extended_max          = stats->cycles + stats->max_seq;

     expected              = extended_max - stats->base_seq;

     lost                  = expected - stats->received;
     lost                  = FFMIN(lost, 0xffffff); // clamp it since it's only 24 bits...
     expected_interval     = expected - stats->expected_prior;

     stats->expected_prior = expected;

     received_interval     = stats->received - stats->received_prior;

     stats->received_prior = stats->received;

     lost_interval         = expected_interval - received_interval;

     if (expected_interval == 0 || lost_interval <= 0)
         fraction = 0;
     else
         fraction = (lost_interval << 8) / expected_interval;
 
     fraction = (fraction << 24) | lost;

     avio_wb32(pb, fraction); /* 8 bits of fraction, 24 bits of total packets lost */
     avio_wb32(pb, extended_max); /* max sequence received */

     avio_wb32(pb, stats->jitter >> 4); /* jitter */

     if (s->last_rtcp_ntp_time == AV_NOPTS_VALUE) {

         avio_wb32(pb, 0); /* last SR timestamp */
         avio_wb32(pb, 0); /* delay since last SR */

     } else {

         uint32_t middle_32_bits   = s->last_rtcp_ntp_time >> 16; // this is valid, right? do we need to handle 64 bit values special?

         uint32_t delay_since_last = av_rescale(av_gettime() - s->last_rtcp_reception_time,
                                                65536, AV_TIME_BASE);

         avio_wb32(pb, middle_32_bits); /* last SR timestamp */
         avio_wb32(pb, delay_since_last); /* delay since last SR */

     }
 
     // CNAME

     avio_w8(pb, (RTP_VERSION << 6) + 1); /* 1 report block */
     avio_w8(pb, RTCP_SDES);

     len = strlen(s->hostname);

     avio_wb16(pb, (7 + len + 3) / 4); /* length in words - 1 */

     avio_wb32(pb, s->ssrc + 1);

     avio_w8(pb, 0x01);
     avio_w8(pb, len);
     avio_write(pb, s->hostname, len);

     avio_w8(pb, 0); /* END */

     // padding

     for (len = (7 + len) % 4; len % 4; len++)

         avio_w8(pb, 0);

     avio_flush(pb);

     if (!fd)
         return 0;

     len = avio_close_dyn_buf(pb, &buf);

     if ((len > 0) && buf) {

         int av_unused result;

         av_dlog(s->ic, "sending %d bytes of RR\n", len);

         result = ffurl_write(fd, buf, len);

         av_dlog(s->ic, "result from ffurl_write: %d\n", result);

         av_free(buf);
     }
     return 0;
 }
 

 void ff_rtp_send_punch_packets(URLContext *rtp_handle)

 {

     AVIOContext *pb;

     uint8_t *buf;
     int len;
 
     /* Send a small RTP packet */

     if (avio_open_dyn_buf(&pb) < 0)

         return;
 

     avio_w8(pb, (RTP_VERSION << 6));
     avio_w8(pb, 0); /* Payload type */
     avio_wb16(pb, 0); /* Seq */
     avio_wb32(pb, 0); /* Timestamp */
     avio_wb32(pb, 0); /* SSRC */

     avio_flush(pb);

     len = avio_close_dyn_buf(pb, &buf);

     if ((len > 0) && buf)

         ffurl_write(rtp_handle, buf, len);

     av_free(buf);
 
     /* Send a minimal RTCP RR */

     if (avio_open_dyn_buf(&pb) < 0)

         return;
 

     avio_w8(pb, (RTP_VERSION << 6));
     avio_w8(pb, RTCP_RR); /* receiver report */
     avio_wb16(pb, 1); /* length in words - 1 */
     avio_wb32(pb, 0); /* our own SSRC */

     avio_flush(pb);

     len = avio_close_dyn_buf(pb, &buf);

     if ((len > 0) && buf)

         ffurl_write(rtp_handle, buf, len);

     av_free(buf);
 }
 

 static int find_missing_packets(RTPDemuxContext *s, uint16_t *first_missing,
                                 uint16_t *missing_mask)
 {
     int i;
     uint16_t next_seq = s->seq + 1;
     RTPPacket *pkt = s->queue;
 
     if (!pkt || pkt->seq == next_seq)
         return 0;
 
     *missing_mask = 0;
     for (i = 1; i <= 16; i++) {
         uint16_t missing_seq = next_seq + i;
         while (pkt) {
             int16_t diff = pkt->seq - missing_seq;
             if (diff >= 0)
                 break;
             pkt = pkt->next;
         }
         if (!pkt)
             break;
         if (pkt->seq == missing_seq)
             continue;
         *missing_mask |= 1 << (i - 1);
     }
 
     *first_missing = next_seq;
     return 1;
 }
 
 int ff_rtp_send_rtcp_feedback(RTPDemuxContext *s, URLContext *fd,
                               AVIOContext *avio)
 {
     int len, need_keyframe, missing_packets;
     AVIOContext *pb;
     uint8_t *buf;
     int64_t now;

     uint16_t first_missing = 0, missing_mask = 0;

 
     if (!fd && !avio)
         return -1;
 
     need_keyframe = s->handler && s->handler->need_keyframe &&
                     s->handler->need_keyframe(s->dynamic_protocol_context);
     missing_packets = find_missing_packets(s, &first_missing, &missing_mask);
 
     if (!need_keyframe && !missing_packets)
         return 0;
 
     /* Send new feedback if enough time has elapsed since the last
      * feedback packet. */
 
     now = av_gettime();
     if (s->last_feedback_time &&
         (now - s->last_feedback_time) < MIN_FEEDBACK_INTERVAL)
         return 0;
     s->last_feedback_time = now;
 
     if (!fd)
         pb = avio;
     else if (avio_open_dyn_buf(&pb) < 0)
         return -1;
 
     if (need_keyframe) {
         avio_w8(pb, (RTP_VERSION << 6) | 1); /* PLI */
         avio_w8(pb, RTCP_PSFB);
         avio_wb16(pb, 2); /* length in words - 1 */
         // our own SSRC: we use the server's SSRC + 1 to avoid conflicts
         avio_wb32(pb, s->ssrc + 1);
         avio_wb32(pb, s->ssrc); // server SSRC
     }
 
     if (missing_packets) {
         avio_w8(pb, (RTP_VERSION << 6) | 1); /* NACK */
         avio_w8(pb, RTCP_RTPFB);
         avio_wb16(pb, 3); /* length in words - 1 */
         avio_wb32(pb, s->ssrc + 1);
         avio_wb32(pb, s->ssrc); // server SSRC
 
         avio_wb16(pb, first_missing);
         avio_wb16(pb, missing_mask);
     }
 
     avio_flush(pb);
     if (!fd)
         return 0;
     len = avio_close_dyn_buf(pb, &buf);
     if (len > 0 && buf) {
         ffurl_write(fd, buf, len);
         av_free(buf);
     }
     return 0;
 }
 

 /**
  * open a new RTP parse context for stream 'st'. 'st' can be NULL for

  * MPEG2-TS streams.

  */

 RTPDemuxContext *ff_rtp_parse_open(AVFormatContext *s1, AVStream *st,

                                    int payload_type, int queue_size)

 {
     RTPDemuxContext *s;
 
     s = av_mallocz(sizeof(RTPDemuxContext));
     if (!s)
         return NULL;

     s->payload_type        = payload_type;
     s->last_rtcp_ntp_time  = AV_NOPTS_VALUE;

     s->first_rtcp_ntp_time = AV_NOPTS_VALUE;

     s->ic                  = s1;
     s->st                  = st;
     s->queue_size          = queue_size;

     rtp_init_statistics(&s->statistics, 0);

     if (st) {

         switch (st->codec->codec_id) {

         case AV_CODEC_ID_ADPCM_G722:

             /* According to RFC 3551, the stream clock rate is 8000
              * even if the sample rate is 16000. */
             if (st->codec->sample_rate == 8000)
                 st->codec->sample_rate = 16000;
             break;

         default:
             break;
         }
     }
     // needed to send back RTCP RR in RTSP sessions
     gethostname(s->hostname, sizeof(s->hostname));
     return s;
 }
 

 void ff_rtp_parse_set_dynamic_protocol(RTPDemuxContext *s, PayloadContext *ctx,
                                        RTPDynamicProtocolHandler *handler)

 {
     s->dynamic_protocol_context = ctx;

     s->handler                  = handler;

 }
 

 void ff_rtp_parse_set_crypto(RTPDemuxContext *s, const char *suite,
                              const char *params)
 {
     if (!ff_srtp_set_crypto(&s->srtp, suite, params))
         s->srtp_enabled = 1;
 }
 

 /**

  * This was the second switch in rtp_parse packet.
  * Normalizes time, if required, sets stream_index, etc.

  */
 static void finalize_packet(RTPDemuxContext *s, AVPacket *pkt, uint32_t timestamp)
 {

     if (pkt->pts != AV_NOPTS_VALUE || pkt->dts != AV_NOPTS_VALUE)
         return; /* Timestamp already set by depacketizer */

     if (timestamp == RTP_NOTS_VALUE)
         return;
 

     if (s->last_rtcp_ntp_time != AV_NOPTS_VALUE && s->ic->nb_streams > 1) {

         int64_t addend;
         int delta_timestamp;
 
         /* compute pts from timestamp with received ntp_time */
         delta_timestamp = timestamp - s->last_rtcp_timestamp;
         /* convert to the PTS timebase */

         addend = av_rescale(s->last_rtcp_ntp_time - s->first_rtcp_ntp_time,
                             s->st->time_base.den,
                             (uint64_t) s->st->time_base.num << 32);

         pkt->pts = s->range_start_offset + s->rtcp_ts_offset + addend +
                    delta_timestamp;
         return;

     }

     if (!s->base_timestamp)
         s->base_timestamp = timestamp;

     /* assume that the difference is INT32_MIN < x < INT32_MAX,
      * but allow the first timestamp to exceed INT32_MAX */

     if (!s->timestamp)
         s->unwrapped_timestamp += timestamp;
     else
         s->unwrapped_timestamp += (int32_t)(timestamp - s->timestamp);
     s->timestamp = timestamp;

     pkt->pts     = s->unwrapped_timestamp + s->range_start_offset -
                    s->base_timestamp;

 }
 

 static int rtp_parse_packet_internal(RTPDemuxContext *s, AVPacket *pkt,
                                      const uint8_t *buf, int len)

 {

     unsigned int ssrc;

     int payload_type, seq, flags = 0;

     int ext, csrc;

     AVStream *st;
     uint32_t timestamp;

     int rv = 0;

     csrc         = buf[0] & 0x0f;

     ext          = buf[0] & 0x10;

     payload_type = buf[1] & 0x7f;

     if (buf[1] & 0x80)
         flags |= RTP_FLAG_MARKER;

     seq       = AV_RB16(buf + 2);

     timestamp = AV_RB32(buf + 4);

     ssrc      = AV_RB32(buf + 8);

     /* store the ssrc in the RTPDemuxContext */
     s->ssrc = ssrc;
 
     /* NOTE: we can handle only one payload type */
     if (s->payload_type != payload_type)
         return -1;
 
     st = s->st;
     // only do something with this if all the rtp checks pass...

     if (!rtp_valid_packet_in_sequence(&s->statistics, seq)) {
         av_log(st ? st->codec : NULL, AV_LOG_ERROR,
                "RTP: PT=%02x: bad cseq %04x expected=%04x\n",

                payload_type, seq, ((s->seq + 1) & 0xffff));
         return -1;
     }
 

     if (buf[0] & 0x20) {
         int padding = buf[len - 1];
         if (len >= 12 + padding)
             len -= padding;
     }
 

     s->seq = seq;

     len   -= 12;
     buf   += 12;

     len   -= 4 * csrc;
     buf   += 4 * csrc;
     if (len < 0)
         return AVERROR_INVALIDDATA;
 

     /* RFC 3550 Section 5.3.1 RTP Header Extension handling */
     if (ext) {
         if (len < 4)
             return -1;
         /* calculate the header extension length (stored as number
          * of 32-bit words) */
         ext = (AV_RB16(buf + 2) + 1) << 2;
 
         if (len < ext)
             return -1;
         // skip past RTP header extension
         len -= ext;
         buf += ext;
     }
 

     if (s->handler && s->handler->parse_packet) {

         rv = s->handler->parse_packet(s->ic, s->dynamic_protocol_context,
                                       s->st, pkt, &timestamp, buf, len, seq,
                                       flags);

     } else if (st) {

         if ((rv = av_new_packet(pkt, len)) < 0)
             return rv;

         memcpy(pkt->data, buf, len);

         pkt->stream_index = st->index;

     } else {
         return AVERROR(EINVAL);

     }

     // now perform timestamp things....
     finalize_packet(s, pkt, timestamp);

     return rv;
 }
 

 void ff_rtp_reset_packet_queue(RTPDemuxContext *s)
 {
     while (s->queue) {
         RTPPacket *next = s->queue->next;
         av_free(s->queue->buf);
         av_free(s->queue);
         s->queue = next;
     }
     s->seq       = 0;
     s->queue_len = 0;
     s->prev_ret  = 0;
 }
 
 static void enqueue_packet(RTPDemuxContext *s, uint8_t *buf, int len)
 {

     uint16_t seq   = AV_RB16(buf + 2);

     RTPPacket **cur = &s->queue, *packet;

 
     /* Find the correct place in the queue to insert the packet */

     while (*cur) {
         int16_t diff = seq - (*cur)->seq;

         if (diff < 0)
             break;

         cur = &(*cur)->next;

     }
 
     packet = av_mallocz(sizeof(*packet));
     if (!packet)
         return;
     packet->recvtime = av_gettime();

     packet->seq      = seq;
     packet->len      = len;
     packet->buf      = buf;

     packet->next     = *cur;
     *cur = packet;

     s->queue_len++;
 }
 
 static int has_next_packet(RTPDemuxContext *s)
 {

     return s->queue && s->queue->seq == (uint16_t) (s->seq + 1);

 }
 
 int64_t ff_rtp_queued_packet_time(RTPDemuxContext *s)
 {
     return s->queue ? s->queue->recvtime : 0;
 }
 
 static int rtp_parse_queued_packet(RTPDemuxContext *s, AVPacket *pkt)
 {
     int rv;
     RTPPacket *next;
 
     if (s->queue_len <= 0)
         return -1;
 
     if (!has_next_packet(s))
         av_log(s->st ? s->st->codec : NULL, AV_LOG_WARNING,
                "RTP: missed %d packets\n", s->queue->seq - s->seq - 1);
 
     /* Parse the first packet in the queue, and dequeue it */

     rv   = rtp_parse_packet_internal(s, pkt, s->queue->buf, s->queue->len);

     next = s->queue->next;
     av_free(s->queue->buf);
     av_free(s->queue);
     s->queue = next;
     s->queue_len--;

     return rv;

 }
 

 static int rtp_parse_one_packet(RTPDemuxContext *s, AVPacket *pkt,

                                 uint8_t **bufptr, int len)

 {

     uint8_t *buf = bufptr ? *bufptr : NULL;

     int flags = 0;

     uint32_t timestamp;

     int rv = 0;

 
     if (!buf) {

         /* If parsing of the previous packet actually returned 0 or an error,
          * there's nothing more to be parsed from that packet, but we may have

          * indicated that we can return the next enqueued packet. */

         if (s->prev_ret <= 0)

             return rtp_parse_queued_packet(s, pkt);

         /* return the next packets, if any */

         if (s->handler && s->handler->parse_packet) {

             /* timestamp should be overwritten by parse_packet, if not,
              * the packet is left with pts == AV_NOPTS_VALUE */
             timestamp = RTP_NOTS_VALUE;

             rv        = s->handler->parse_packet(s->ic, s->dynamic_protocol_context,
                                                  s->st, pkt, &timestamp, NULL, 0, 0,
                                                  flags);

             finalize_packet(s, pkt, timestamp);

             return rv;

         }
     }
 
     if (len < 12)
         return -1;
 
     if ((buf[0] & 0xc0) != (RTP_VERSION << 6))
         return -1;

     if (RTP_PT_IS_RTCP(buf[1])) {

         return rtcp_parse_packet(s, buf, len);
     }
 

     if (s->st) {
         int64_t received = av_gettime();
         uint32_t arrival_ts = av_rescale_q(received, AV_TIME_BASE_Q,
                                            s->st->time_base);
         timestamp = AV_RB32(buf + 4);
         // Calculate the jitter immediately, before queueing the packet
         // into the reordering queue.
         rtcp_update_jitter(&s->statistics, timestamp, arrival_ts);
     }
 

     if ((s->seq == 0 && !s->queue) || s->queue_size <= 1) {

         /* First packet, or no reordering */
         return rtp_parse_packet_internal(s, pkt, buf, len);
     } else {
         uint16_t seq = AV_RB16(buf + 2);
         int16_t diff = seq - s->seq;
         if (diff < 0) {
             /* Packet older than the previously emitted one, drop */
             av_log(s->st ? s->st->codec : NULL, AV_LOG_WARNING,
                    "RTP: dropping old packet received too late\n");
             return -1;
         } else if (diff <= 1) {
             /* Correct packet */
             rv = rtp_parse_packet_internal(s, pkt, buf, len);

             return rv;

         } else {
             /* Still missing some packet, enqueue this one. */
             enqueue_packet(s, buf, len);
             *bufptr = NULL;
             /* Return the first enqueued packet if the queue is full,
              * even if we're missing something */
             if (s->queue_len >= s->queue_size)
                 return rtp_parse_queued_packet(s, pkt);
             return -1;
         }
     }

 }
 

 /**
  * Parse an RTP or RTCP packet directly sent as a buffer.
  * @param s RTP parse context.
  * @param pkt returned packet
  * @param bufptr pointer to the input buffer or NULL to read the next packets
  * @param len buffer len
  * @return 0 if a packet is returned, 1 if a packet is returned and more can follow
  * (use buf as NULL to read the next). -1 if no packet (error or no more packet).
  */

 int ff_rtp_parse_packet(RTPDemuxContext *s, AVPacket *pkt,
                         uint8_t **bufptr, int len)

 {

     int rv;
     if (s->srtp_enabled && bufptr && ff_srtp_decrypt(&s->srtp, *bufptr, &len) < 0)
         return -1;
     rv = rtp_parse_one_packet(s, pkt, bufptr, len);

     s->prev_ret = rv;

     while (rv == AVERROR(EAGAIN) && has_next_packet(s))
         rv = rtp_parse_queued_packet(s, pkt);

     return rv ? rv : has_next_packet(s);
 }
 

 void ff_rtp_parse_close(RTPDemuxContext *s)

 {

     ff_rtp_reset_packet_queue(s);

     ff_srtp_free(&s->srtp);

     av_free(s);
 }

 
 int ff_parse_fmtp(AVStream *stream, PayloadContext *data, const char *p,
                   int (*parse_fmtp)(AVStream *stream,
                                     PayloadContext *data,
                                     char *attr, char *value))
 {
     char attr[256];

     char *value;

     int res;

     int value_size = strlen(p) + 1;
 
     if (!(value = av_malloc(value_size))) {

         av_log(NULL, AV_LOG_ERROR, "Failed to allocate data for FMTP.\n");

         return AVERROR(ENOMEM);
     }

 
     // remove protocol identifier

     while (*p && *p == ' ')
         p++;                     // strip spaces
     while (*p && *p != ' ')
         p++;                     // eat protocol identifier
     while (*p && *p == ' ')
         p++;                     // strip trailing spaces

 
     while (ff_rtsp_next_attr_and_value(&p,
                                        attr, sizeof(attr),

                                        value, value_size)) {

         res = parse_fmtp(stream, data, attr, value);

         if (res < 0 && res != AVERROR_PATCHWELCOME) {
             av_free(value);

             return res;

         }

     }

     av_free(value);

     return 0;
 }

 
 int ff_rtp_finalize_packet(AVPacket *pkt, AVIOContext **dyn_buf, int stream_idx)
 {

     int ret;

     av_init_packet(pkt);
 

     pkt->size         = avio_close_dyn_buf(*dyn_buf, &pkt->data);

     pkt->stream_index = stream_idx;

     *dyn_buf = NULL;
     if ((ret = av_packet_from_data(pkt, pkt->data, pkt->size)) < 0) {
         av_freep(&pkt->data);
         return ret;
     }

     return pkt->size;
 }