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538 lines
16 KiB
538 lines
16 KiB
/**
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* @file session.c
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* @brief RTP session handling
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*/
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/*****************************************************************************
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* Copyright © 2008 Rémi Denis-Courmont
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 2.1
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* of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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****************************************************************************/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <stdlib.h>
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#include <assert.h>
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#include <errno.h>
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#include <vlc_common.h>
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#include <vlc_demux.h>
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#include "rtp.h"
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typedef struct rtp_source_t rtp_source_t;
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/** State for a RTP session: */
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struct rtp_session_t
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{
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rtp_source_t **srcv;
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unsigned srcc;
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uint8_t ptc;
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rtp_pt_t **ptv;
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/* params */
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vlc_tick_t timeout;
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uint16_t max_dropout; /**< Max packet forward misordering */
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uint16_t max_misorder; /**< Max packet backward misordering */
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uint8_t max_src; /**< Max simultaneous RTP sources */
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};
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static rtp_source_t *
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rtp_source_create (struct vlc_logger *, const rtp_session_t *, uint32_t, uint16_t);
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static void rtp_source_destroy(struct vlc_logger *, rtp_source_t *);
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static void rtp_decode (struct vlc_logger *, const rtp_session_t *, rtp_source_t *);
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/**
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* Creates a new RTP session.
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*/
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rtp_session_t *
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rtp_session_create_custom (uint16_t max_dropout, uint16_t max_misorder,
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uint8_t max_src, vlc_tick_t timeout)
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{
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rtp_session_t *session = malloc (sizeof (*session));
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if (session == NULL)
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return NULL;
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/* fixed parameters */
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session->max_dropout = max_dropout;
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session->max_misorder = -1 * max_misorder;
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session->max_src = max_src;
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session->timeout = timeout;
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/* state variables */
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session->srcv = NULL;
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session->srcc = 0;
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session->ptc = 0;
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session->ptv = NULL;
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return session;
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}
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rtp_session_t *
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rtp_session_create (void)
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{
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return rtp_session_create_custom(RTP_MAX_DROPOUT_DEFAULT,
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RTP_MAX_MISORDER_DEFAULT,
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RTP_MAX_SRC_DEFAULT,
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RTP_MAX_TIMEOUT_DEFAULT);
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}
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/**
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* Destroys an RTP session.
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*/
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void rtp_session_destroy (struct vlc_logger *logger, rtp_session_t *session)
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{
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for (unsigned i = 0; i < session->srcc; i++)
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rtp_source_destroy(logger, session->srcv[i]);
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for (uint_fast8_t i = 0; i < session->ptc; i++)
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vlc_rtp_pt_release(session->ptv[i]);
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free (session->srcv);
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free (session->ptv);
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free (session);
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}
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/**
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* Adds a payload type to an RTP session.
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*/
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int rtp_add_type(rtp_session_t *ses, rtp_pt_t *pt)
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{
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assert(pt->frequency > 0); /* SIGFPE! */
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if (ses->srcc > 0)
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return EBUSY;
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rtp_pt_t **ppt = realloc(ses->ptv, (ses->ptc + 1) * sizeof (pt));
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if (ppt == NULL)
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return ENOMEM;
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ses->ptv = ppt;
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ses->ptv[ses->ptc++] = pt;
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return 0;
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}
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/** State for an RTP source */
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struct rtp_source_t
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{
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uint32_t ssrc;
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uint32_t jitter; /* interarrival delay jitter estimate */
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vlc_tick_t last_rx; /* last received packet local timestamp */
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uint32_t last_ts; /* last received packet RTP timestamp */
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uint32_t ref_rtp; /* sender RTP timestamp reference */
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vlc_tick_t ref_ntp; /* sender NTP timestamp reference */
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uint16_t bad_seq; /* tentatively next expected sequence for resync */
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uint16_t max_seq; /* next expected sequence */
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uint16_t last_seq; /* sequence of the next dequeued packet */
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block_t *blocks; /* re-ordered blocks queue */
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struct {
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struct vlc_rtp_pt *instance; /* Per-source current payload format */
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void *opaque; /* Per-source payload format private data */
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} pt;
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};
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/**
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* Initializes a new RTP source within an RTP session.
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*/
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static rtp_source_t *
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rtp_source_create (struct vlc_logger *logger, const rtp_session_t *session,
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uint32_t ssrc, uint16_t init_seq)
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{
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rtp_source_t *source;
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source = malloc (sizeof (*source) + (sizeof (void *) * session->ptc));
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if (source == NULL)
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return NULL;
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source->ssrc = ssrc;
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source->jitter = 0;
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source->ref_rtp = 0;
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source->ref_ntp = UINT64_C (1) << 51;
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source->max_seq = source->bad_seq = init_seq;
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source->last_seq = init_seq - 1;
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source->blocks = NULL;
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source->pt.instance = NULL;
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vlc_debug (logger, "added RTP source (%08x)", ssrc);
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return source;
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}
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/**
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* Destroys an RTP source and its associated streams.
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*/
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static void rtp_source_destroy(struct vlc_logger *logger, rtp_source_t *source)
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{
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vlc_debug (logger, "removing RTP source (%08x)", source->ssrc);
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if (source->pt.instance != NULL)
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vlc_rtp_pt_end(source->pt.instance, source->pt.opaque);
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block_ChainRelease (source->blocks);
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free (source);
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}
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static inline uint16_t rtp_seq (const block_t *block)
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{
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assert (block->i_buffer >= 4);
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return GetWBE (block->p_buffer + 2);
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}
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static inline uint32_t rtp_timestamp (const block_t *block)
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{
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assert (block->i_buffer >= 12);
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return GetDWBE (block->p_buffer + 4);
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}
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static struct vlc_rtp_pt *rtp_find_ptype(const rtp_session_t *session,
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const block_t *block)
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{
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uint8_t ptype = rtp_ptype (block);
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for (unsigned i = 0; i < session->ptc; i++)
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{
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struct vlc_rtp_pt *pt = session->ptv[i];
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if (pt->number == ptype)
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return pt;
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}
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return NULL;
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}
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/**
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* Receives an RTP packet and queues it. Not a cancellation point.
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*
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* @param logger VLC logger handle
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* @param session RTP session receiving the packet
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* @param block RTP packet including the RTP header
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*/
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void
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rtp_queue (struct vlc_logger *logger, rtp_session_t *session, block_t *block)
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{
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/* RTP header sanity checks (see RFC 3550) */
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if (block->i_buffer < 12)
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goto drop;
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if ((block->p_buffer[0] >> 6 ) != 2) /* RTP version number */
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goto drop;
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/* Remove padding if present */
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if (block->p_buffer[0] & 0x20)
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{
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uint8_t padding = block->p_buffer[block->i_buffer - 1];
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if ((padding == 0) || (block->i_buffer < (12u + padding)))
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goto drop; /* illegal value */
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block->i_buffer -= padding;
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}
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vlc_tick_t now = vlc_tick_now ();
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rtp_source_t *src = NULL;
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const uint16_t seq = rtp_seq (block);
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const uint32_t ssrc = GetDWBE (block->p_buffer + 8);
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/* In most case, we know this source already */
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for (unsigned i = 0, max = session->srcc; i < max; i++)
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{
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rtp_source_t *tmp = session->srcv[i];
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if (tmp->ssrc == ssrc)
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{
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src = tmp;
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break;
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}
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/* RTP source garbage collection */
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if ((tmp->last_rx + session->timeout) < now)
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{
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rtp_source_destroy(logger, tmp);
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if (--session->srcc > 0)
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session->srcv[i] = session->srcv[session->srcc - 1];
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}
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}
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if (src == NULL)
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{
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/* New source */
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if (session->srcc >= session->max_src)
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{
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vlc_warning (logger, "too many RTP sessions");
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goto drop;
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}
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rtp_source_t **tab;
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tab = realloc (session->srcv, (session->srcc + 1) * sizeof (*tab));
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if (tab == NULL)
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goto drop;
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session->srcv = tab;
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src = rtp_source_create (logger, session, ssrc, seq);
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if (src == NULL)
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goto drop;
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tab[session->srcc++] = src;
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/* Cannot compute jitter yet */
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}
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else
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{
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const rtp_pt_t *pt = rtp_find_ptype(session, block);
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if (pt != NULL)
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{
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/* Recompute jitter estimate.
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* That is computed from the RTP timestamps and the system clock.
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* It is independent of RTP sequence. */
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uint32_t freq = pt->frequency;
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int64_t ts = rtp_timestamp (block);
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int64_t d = samples_from_vlc_tick(now - src->last_rx, freq);
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d -= ts - src->last_ts;
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if (d < 0) d = -d;
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src->jitter += ((d - src->jitter) + 8) >> 4;
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}
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}
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src->last_rx = now;
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block->i_pts = now; /* store reception time until dequeued */
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src->last_ts = rtp_timestamp (block);
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/* Check sequence number */
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/* NOTE: the sequence number is per-source,
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* but is independent from the payload type. */
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union {
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uint16_t u;
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int16_t s;
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} delta_seq = { .u = seq - src->max_seq };
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if ((delta_seq.s >= 0) ? (delta_seq.u > session->max_dropout)
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: (delta_seq.u < session->max_misorder))
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{
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vlc_debug (logger, "sequence discontinuity"
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" (got: %"PRIu16", expected: %"PRIu16")", seq, src->max_seq);
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if (seq == src->bad_seq)
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{
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src->max_seq = src->bad_seq = seq + 1;
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src->last_seq = seq - 0x7fffe; /* hack for rtp_decode() */
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vlc_warning (logger, "sequence resynchronized");
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block_ChainRelease (src->blocks);
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src->blocks = NULL;
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}
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else
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{
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src->bad_seq = seq + 1;
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goto drop;
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}
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}
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else
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if (delta_seq.s >= 0)
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src->max_seq = seq + 1;
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/* Queues the block in sequence order,
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* hence there is a single queue for all payload types. */
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block_t **pp = &src->blocks;
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for (block_t *prev = *pp; prev != NULL; prev = *pp)
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{
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delta_seq.u = seq - rtp_seq (prev);
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if (delta_seq.s < 0)
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break;
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if (delta_seq.s == 0)
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{
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vlc_debug (logger, "duplicate packet (sequence: %"PRIu16")", seq);
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goto drop; /* duplicate */
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}
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pp = &prev->p_next;
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}
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block->p_next = *pp;
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*pp = block;
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/*rtp_decode (demux, session, src);*/
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return;
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drop:
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block_Release (block);
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}
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/**
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* Dequeues RTP packets and pass them to decoder. Not cancellation-safe(?).
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* A packet is decoded if it is the next in sequence order, or if we have
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* given up waiting on the missing packets (time out) from the last one
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* already decoded.
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*
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* @param logger pointer to VLC logger
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* @param session RTP session receiving the packet
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* @param now monotonic clock reference for packets timing (ex: vlc_tick_now())
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* @param deadlinep pointer to deadline to call rtp_dequeue() again
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* @return true if the buffer is not empty, false otherwise.
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* In the later case, *deadlinep is undefined.
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*/
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bool rtp_dequeue (struct vlc_logger *logger, const rtp_session_t *session,
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vlc_tick_t now, vlc_tick_t *restrict deadlinep)
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{
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bool pending = false;
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*deadlinep = VLC_TICK_MAX;
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for (unsigned i = 0, max = session->srcc; i < max; i++)
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{
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rtp_source_t *src = session->srcv[i];
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block_t *block;
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/* Because of IP packet delay variation (IPDV), we need to guesstimate
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* how long to wait for a missing packet in the RTP sequence
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* (see RFC3393 for background on IPDV).
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*
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* This situation occurs if a packet got lost, or if the network has
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* re-ordered packets. Unfortunately, the MSL is 2 minutes, orders of
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* magnitude too long for multimedia. We need a trade-off.
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* If we underestimated IPDV, we may have to discard valid but late
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* packets. If we overestimate it, we will either cause too much
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* delay, or worse, underflow our downstream buffers, as we wait for
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* definitely a lost packets.
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*
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* The rest of the "de-jitter buffer" work is done by the internal
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* LibVLC E/S-out clock synchronization. Here, we need to bother about
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* re-ordering packets, as decoders can't cope with mis-ordered data.
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*/
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while (((block = src->blocks)) != NULL)
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{
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if ((int16_t)(rtp_seq (block) - (src->last_seq + 1)) <= 0)
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{ /* Next (or earlier) block ready, no need to wait */
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rtp_decode (logger, session, src);
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continue;
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}
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/* Wait for 3 times the inter-arrival delay variance (about 99.7%
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* match for random gaussian jitter).
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*/
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vlc_tick_t deadline;
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const rtp_pt_t *pt = rtp_find_ptype(session, block);
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if (pt)
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deadline = vlc_tick_from_samples(3 * src->jitter, pt->frequency);
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else
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deadline = 0; /* no jitter estimate with no frequency :( */
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/* Make sure we wait at least for 25 msec */
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if (deadline < VLC_TICK_FROM_MS(25))
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deadline = VLC_TICK_FROM_MS(25);
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/* Additionally, we implicitly wait for the packetization time
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* multiplied by the number of missing packets. block is the first
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* non-missing packet (lowest sequence number). We have no better
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* estimated time of arrival, as we do not know the RTP timestamp
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* of not yet received packets. */
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deadline += block->i_pts;
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if (now >= deadline)
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{
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rtp_decode (logger, session, src);
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continue;
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}
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if (*deadlinep > deadline)
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*deadlinep = deadline;
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pending = true; /* packet pending in buffer */
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break;
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}
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}
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return pending;
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}
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/**
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* Decodes one RTP packet.
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*/
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static void
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rtp_decode (struct vlc_logger *logger, const rtp_session_t *session, rtp_source_t *src)
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{
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block_t *block = src->blocks;
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assert (block);
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src->blocks = block->p_next;
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block->p_next = NULL;
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/* Discontinuity detection */
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uint16_t delta_seq = rtp_seq (block) - (src->last_seq + 1);
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if (delta_seq != 0)
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{
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if (delta_seq >= 0x8000)
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{ /* Trash too late packets (and PIM Assert duplicates) */
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vlc_debug (logger, "ignoring late packet (sequence: %"PRIu16")",
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rtp_seq (block));
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goto drop;
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}
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vlc_warning (logger, "%"PRIu16" packet(s) lost", delta_seq);
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block->i_flags |= BLOCK_FLAG_DISCONTINUITY;
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}
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src->last_seq = rtp_seq (block);
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/* Match the payload type */
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struct vlc_rtp_pt *pt = rtp_find_ptype(session, block);
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if (pt == NULL)
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{
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vlc_debug (logger, "unknown payload (%"PRIu8")",
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rtp_ptype (block));
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goto drop;
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}
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if (src->pt.instance != pt) {
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/* Change the active payload type for this source. */
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if (src->pt.instance != NULL)
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vlc_rtp_pt_end(src->pt.instance, src->pt.opaque);
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src->pt.instance = pt;
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src->pt.opaque = vlc_rtp_pt_begin(pt);
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}
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/* Computes the PTS from the RTP timestamp and payload RTP frequency.
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* DTS is unknown. Also, while the clock frequency depends on the payload
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* format, a single source MUST only use payloads of a chosen frequency.
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* Otherwise it would be impossible to compute consistent timestamps. */
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const uint32_t timestamp = rtp_timestamp (block);
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union {
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uint32_t u;
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int32_t s;
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} ts_delta = { .u = timestamp - src->ref_rtp };
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vlc_tick_t ticks = vlc_tick_from_samples(ts_delta.s, pt->frequency);
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block->i_pts = src->ref_ntp + ticks;
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/* TODO: proper inter-medias/sessions sync (using RTCP-SR) */
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src->ref_ntp = block->i_pts;
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src->ref_rtp = timestamp;
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|
|
/* CSRC count */
|
|
size_t skip = 12u + (block->p_buffer[0] & 0x0F) * 4;
|
|
|
|
/* Extension header (ignored for now) */
|
|
if (block->p_buffer[0] & 0x10)
|
|
{
|
|
skip += 4;
|
|
if (block->i_buffer < skip)
|
|
goto drop;
|
|
|
|
skip += 4 * GetWBE (block->p_buffer + skip - 2);
|
|
}
|
|
|
|
if (block->i_buffer < skip)
|
|
goto drop;
|
|
|
|
struct vlc_rtp_pktinfo pktinfo = {
|
|
.m = block->p_buffer[1] >> 7,
|
|
/* TODO: extension headers (e.g. AV-1 deps) */
|
|
};
|
|
|
|
block->p_buffer += skip;
|
|
block->i_buffer -= skip;
|
|
|
|
vlc_rtp_pt_decode(pt, src->pt.opaque, block, &pktinfo);
|
|
return;
|
|
|
|
drop:
|
|
block_Release (block);
|
|
}
|
|
|