/*------------------------------------------------------------------------- * rtpupdate.c - rtpupdate, rtpinitseq, rtpupdateseq *------------------------------------------------------------------------- */#include "hust_rtp.h"#include "hust_util.h"#include "hust_event.h"#include "hust_linux.h"#include "hust_hash.h"///#include <time.h>#define DEBUG(x) x/*------------------------------------------------------------------------ * rtpupdate - update statistics with each RTP packet received.  *------------------------------------------------------------------------ */intrtpupdate(struct session *psn, struct stream *pstm, struct rtp *header){	u32_t		now;	s32_t		delta;	s32_t		D;	////if (pthread_mutex_lock(&pstm->stm_mutex) != 0)	///	return ERROR;	if (rtpupdateseq(psn, pstm, header->rtp_seq) == ERROR) {		////pthread_mutex_unlock(&pstm->stm_mutex);		return ERROR;	}	now=timer_get_ticks();	/*	 * Check for encoding change.	 * Post event if detected.	 */	if (pstm->stm_payload != header->rtp_payload) {		pstm->stm_payload = header->rtp_payload;		rtppostevent(psn, EVENT_PARTICIPANT_ENCODING, pstm->stm_ssrc, NULL, 0);	}  ////檢查編碼(載荷類型payload)的變化，并發出事件通知	/*	 * If not first packet, update jitter.	 */	if (pstm->stm_packets != 0) {		if (pstm->stm_clkrt != 0) {			delta = timeflatten(timesub(now, pstm->stm_lastrec), pstm->stm_clkrt);			D = delta - (header->rtp_time - pstm->stm_lastts);			D = (D < 0 ? -D : D);			pstm->stm_jitter += ((double) D - pstm->stm_jitter) / (double) 16;		}	}	///刷新時間抖動  	pstm->stm_packets++;	pstm->stm_inactive = 0;	pstm->stm_lastts = header->rtp_time;	pstm->stm_lastrec = now;	////pthread_mutex_unlock(&pstm->stm_mutex);	return OK;}////收到一個包后刷新統計信息/*------------------------------------------------------------------------ * rtpinitseq - initialize variables related to sequence numbers * Adapted from RFC 1889. *------------------------------------------------------------------------ */voidrtpinitseq(struct stream *pstm, seq_t seq){	pstm->stm_firstseq = seq;	pstm->stm_hiseq = seq;	pstm->stm_roll = 0;	pstm->stm_packets = 0;	pstm->stm_recprior = 0;	pstm->stm_expprior = 0;  }/*------------------------------------------------------------------------ * rtpupdateseq - check sequence number of incoming packet and update * appropriate counters. Adapted from RFC 1889. *------------------------------------------------------------------------ */intrtpupdateseq(struct session *psn, struct stream *pstm, seq_t seq)////sep是接收到的rtp包的sequence////pstm是根據接收的rtp包的源標識位查詢或創建的stream的指針{	seq_t udelta;	udelta = seq - pstm->stm_hiseq;////計算接收到的包的序列號與所收到的包的最大的序列號的差  	if (pstm->stm_probation) {		/////如果還在檢查期(由stm_probation標識)		if (seq == pstm->stm_hiseq + 1) {			////如果收到序列號連續的包			pstm->stm_probation--;////檢查期標識減一						pstm->stm_hiseq = seq;///刷新流中的最高序列號記錄						if (pstm->stm_probation == 0) {				///過了檢查期則為這個流初始化queue				rtpinitseq(pstm, seq);				return OK;			}		} else {			pstm->stm_probation = RTP_MINSEQUENTIAL - 1;			pstm->stm_hiseq = seq;			////連續的包中斷，重新設置檢查期長度，并把這個包設的序列號			////設置成隊列中最大的		}		return ERROR;	} 	else if (udelta < RTP_MAXDROPOUT) {			////限制seq的跳躍不超過RTP_MAXDROPOUT			if (seq < pstm->stm_hiseq)				pstm->stm_roll++;			////表明進入了下一個周期			pstm->stm_hiseq = seq;			///刷新stm_hiseq		}	else if (udelta <= RTP_SEQMOD - RTP_MAXMISORDER) {				////如果跳躍太大，要根據stm_badseq來確定是否需要重新				////初始化隊列				if (seq == pstm->stm_badseq) {					rtpinitseq(pstm, seq);					rtppostevent(psn, EVENT_PARTICIPANT_SEQGAP,						     pstm->stm_ssrc, NULL, 0);				}			}	else {				pstm->stm_badseq = (seq + 1) & (RTP_SEQMOD - 1);				////跳躍超出范圍，存當前的seq為stm_badseq				return ERROR;			}					return OK;}////通過seq來確定是否讓一個stream度過檢查期，并解決序列號前////后跳躍過大的情況。