请求播放

流连接建立之后，就可以请求播放了。

先看一下请求播放的流程是怎么样的，具体操作如下：

    1、客户端发送命令“播放”给服务器    2、服务器接收到命令之后，发送消息“设置块大小”给客户端    3、服务器发送“stream begin”给客户端，告诉客户端 流的id    4、播放命令成功的话，服务器发送“响应状态”给客户端，告诉客户端播放成功    5、服务器发送音视频数据给客户端

关键的代码同样在HandleInvoke函数中

/*** 处理命令消息** 这些命令消息是使用AMF0格式进行编码的** 下面的代码是精简过的*/static intHandleInvoke(RTMP *r, const char *body, unsigned int nBodySize){	AMFObject obj;	AVal method;	double txn;	int ret = 0, nRes;	char pbuf[256], *pend = pbuf + sizeof(pbuf), *enc, **params = NULL;	char *host = r->Link.hostname.av_len ? r->Link.hostname.av_val : "";	char *pageUrl = r->Link.pageUrl.av_len ? r->Link.pageUrl.av_val : "";	int param_count;	AVal av_Command, av_Response;	if (body[0] != 0x02)		/* make sure it is a string method name we start with */	{		RTMP_Log(RTMP_LOGWARNING, "%s, Sanity failed. no string method in invoke packet",			__FUNCTION__);		return 0;	}	nRes = AMF_Decode(&obj, body, nBodySize, FALSE);	if (nRes < 0)	{		RTMP_Log(RTMP_LOGERROR, "%s, error decoding invoke packet", __FUNCTION__);		return 0;	}	AMF_Dump(&obj);	AMFPRop_GetString(AMF_GetProp(&obj, NULL, 0), &method);	txn = AMFProp_GetNumber(AMF_GetProp(&obj, NULL, 1));	RTMP_Log(RTMP_LOGDEBUG, "%s, server invoking <%s>", __FUNCTION__, method.av_val);	// 处理”result“	if (AVMATCH(&method, &av__result))	{		AVal methodInvoked = { 0 };		int i;		for (i = 0; i < r->m_numCalls; i++) {			if (r->m_methodCalls[i].num == (int)txn) {				methodInvoked = r->m_methodCalls[i].name;				AV_erase(r->m_methodCalls, &r->m_numCalls, i, FALSE);				break;			}		}		if (!methodInvoked.av_val) {			RTMP_Log(RTMP_LOGDEBUG, "%s, received result id %f without matching request",				__FUNCTION__, txn);			goto leave;		}		RTMP_Log(RTMP_LOGDEBUG, "%s, received result for method call <%s>", __FUNCTION__,			methodInvoked.av_val);		// ”connect“命令完成		if (AVMATCH(&methodInvoked, &av_connect))		{			if (r->Link.token.av_len)			{				AMFObjectProperty p;				if (RTMP_FindFirstMatchingProperty(&obj, &av_secureToken, &p))				{					DecodeTEA(&r->Link.token, &p.p_vu.p_aval);					SendSecureTokenResponse(r, &p.p_vu.p_aval);				}			}			if (r->Link.protocol & RTMP_FEATURE_WRITE)			{				SendReleaseStream(r);				SendFCPublish(r);			}			else			{				// 向服务器发送”确认窗口大小“				RTMP_SendServerBW(r);				RTMP_SendCtrl(r, 3, 0, 300);			}						// 删除无关代码***						// 创建流			RTMP_SendCreateStream(r);		}		// 删除无关代码***				// ”创建流“命令成功		else if (AVMATCH(&methodInvoked, &av_createStream))		{			r->m_stream_id = (int)AMFProp_GetNumber(AMF_GetProp(&obj, NULL, 3));			// 删除无关代码***			if (r->Link.protocol & RTMP_FEATURE_WRITE)			{				SendPublish(r);			}			else			{				if (r->Link.lFlags & RTMP_LF_PLST)					SendPlaylist(r);								// 发送播放命令				SendPlay(r);				RTMP_SendCtrl(r, 3, r->m_stream_id, r->m_nBufferMS);			}		}		else if (AVMATCH(&methodInvoked, &av_play) ||			AVMATCH(&methodInvoked, &av_publish))		{			r->m_bPlaying = TRUE;		}		free(methodInvoked.av_val);	}	else if (AVMATCH(&method, &av_onBWDone))	{		if (!r->m_nBWCheckCounter)			SendCheckBW(r);	}	// 删除其他代码***	// ***	// 删除其他代码***leave:	AMF_Reset(&obj);	return ret;}可以看到，创建流完成之后，即else if (AVMATCH(&methodInvoked, &av_createStream))条件判断里面，调用了SendPlay函数，用来发送播放命令。
客户端发送播放命令
static intSendPlay(RTMP *r){	RTMPPacket packet;	char pbuf[1024], *pend = pbuf + sizeof(pbuf);	char *enc;	packet.m_nChannel = 0x08;	/* we make 8 our stream channel */	packet.m_headerType = RTMP_PACKET_SIZE_LARGE;	packet.m_packetType = RTMP_PACKET_TYPE_INVOKE;	packet.m_nTimeStamp = 0;	packet.m_nInfoField2 = r->m_stream_id;	/*0x01000000; */	packet.m_hasAbsTimestamp = 0;	packet.m_body = pbuf + RTMP_MAX_HEADER_SIZE;	enc = packet.m_body;	// 播放命令	enc = AMF_EncodeString(enc, pend, &av_play);	enc = AMF_EncodeNumber(enc, pend, ++r->m_numInvokes);	*enc++ = AMF_NULL;	RTMP_Log(RTMP_LOGDEBUG, "%s, seekTime=%d, stopTime=%d, sending play: %s",		__FUNCTION__, r->Link.seekTime, r->Link.stopTime,		r->Link.playpath.av_val);	enc = AMF_EncodeString(enc, pend, &r->Link.playpath);	if (!enc)		return FALSE;	/* Optional parameters start and len.	 *	 * start: -2, -1, 0, positive number	 *  -2: looks for a live stream, then a recorded stream,	 *      if not found any open a live stream	 *  -1: plays a live stream	 * >=0: plays a recorded streams from 'start' milliseconds	 */	if (r->Link.lFlags & RTMP_LF_LIVE)		enc = AMF_EncodeNumber(enc, pend, -1000.0);	else	{		if (r->Link.seekTime > 0.0 || r->Link.stopTime)			enc = AMF_EncodeNumber(enc, pend, r->Link.seekTime); /* resume from here */	}	if (!enc)		return FALSE;	/* len: -1, 0, positive number	 *  -1: plays live or recorded stream to the end (default)	 *   0: plays a frame 'start' ms away from the beginning	 *  >0: plays a live or recoded stream for 'len' milliseconds	 */	/*enc += EncodeNumber(enc, -1.0); */ /* len */	if (r->Link.stopTime)	{		enc = AMF_EncodeNumber(enc, pend, r->Link.stopTime - r->Link.seekTime);		if (!enc)			return FALSE;	}	packet.m_nBodySize = enc - packet.m_body;	// 发送数据包	return RTMP_SendPacket(r, &packet, TRUE);}
服务器发送“设置块大小”命令
服务器接收到“播放”命令之后，就向客户端回应“设置块大小”命令，处理这个命令的函数是HandleChangeChunkSize
static voidHandleChangeChunkSize(RTMP *r, const RTMPPacket *packet){	if (packet->m_nBodySize >= 4)	{		r->m_inChunkSize = AMF_DecodeInt32(packet->m_body);		RTMP_Log(RTMP_LOGDEBUG, "%s, received: chunk size change to %d", __FUNCTION__,			r->m_inChunkSize);	}}
服务器发送“stream begin”命令
服务器发送完“设置块大小”命令之后，还会继续发送“stream begin”命令，这个命令由HandleCtrl函数处理
/*** 处理用户控制消息，主要用于控制流的各种状态*/static voidHandleCtrl(RTMP *r, const RTMPPacket *packet){	short nType = -1;	unsigned int tmp;	if (packet->m_body && packet->m_nBodySize >= 2)		nType = AMF_DecodeInt16(packet->m_body);	RTMP_Log(RTMP_LOGDEBUG, "%s, received ctrl, type: %d, len: %d", __FUNCTION__, nType,		packet->m_nBodySize);	/*RTMP_LogHex(packet.m_body, packet.m_nBodySize); */	if (packet->m_nBodySize >= 6)	{		switch (nType)		{			// 流开始		case 0:			tmp = AMF_DecodeInt32(packet->m_body + 2);			RTMP_Log(RTMP_LOGDEBUG, "%s, Stream Begin %d", __FUNCTION__, tmp);			break;					// 删除无关代码***		}	}	// 删除无关代码***}
服务器发送“响应状态”信息
服务器发送完“stream begin”之后，根据播放是否成功发送“响应状态”信息给客户端，处理这个消息的函数是HandleInvoke
/*** 处理命令消息** 这些命令消息是使用AMF0格式进行编码的*/static intHandleInvoke(RTMP *r, const char *body, unsigned int nBodySize){	AMFObject obj;	AVal method;	double txn;	int ret = 0, nRes;	char pbuf[256], *pend = pbuf + sizeof(pbuf), *enc, **params = NULL;	char *host = r->Link.hostname.av_len ? r->Link.hostname.av_val : "";	char *pageUrl = r->Link.pageUrl.av_len ? r->Link.pageUrl.av_val : "";	int param_count;	AVal av_Command, av_Response;	if (body[0] != 0x02)		/* make sure it is a string method name we start with */	{		RTMP_Log(RTMP_LOGWARNING, "%s, Sanity failed. no string method in invoke packet",			__FUNCTION__);		return 0;	}	nRes = AMF_Decode(&obj, body, nBodySize, FALSE);	if (nRes < 0)	{		RTMP_Log(RTMP_LOGERROR, "%s, error decoding invoke packet", __FUNCTION__);		return 0;	}	AMF_Dump(&obj);	AMFProp_GetString(AMF_GetProp(&obj, NULL, 0), &method);	txn = AMFProp_GetNumber(AMF_GetProp(&obj, NULL, 1));	RTMP_Log(RTMP_LOGDEBUG, "%s, server invoking <%s>", __FUNCTION__, method.av_val);	if (AVMATCH(&method, &av__result))	{		AVal methodInvoked = { 0 };		int i;		for (i = 0; i < r->m_numCalls; i++) {			if (r->m_methodCalls[i].num == (int)txn) {				methodInvoked = r->m_methodCalls[i].name;				AV_erase(r->m_methodCalls, &r->m_numCalls, i, FALSE);				break;			}		}		if (!methodInvoked.av_val) {			RTMP_Log(RTMP_LOGDEBUG, "%s, received result id %f without matching request",				__FUNCTION__, txn);			goto leave;		}		RTMP_Log(RTMP_LOGDEBUG, "%s, received result for method call <%s>", __FUNCTION__,			methodInvoked.av_val);			// 设置播放成功		if (AVMATCH(&methodInvoked, &av_play) ||			AVMATCH(&methodInvoked, &av_publish))		{			r->m_bPlaying = TRUE;		}		free(methodInvoked.av_val);	}	// 删除无关代码***	// 处理响应状态 	else if (AVMATCH(&method, &av_onStatus))	{		AMFObject obj2;		AVal code, level;		AMFProp_GetObject(AMF_GetProp(&obj, NULL, 3), &obj2);		AMFProp_GetString(AMF_GetProp(&obj2, &av_code, -1), &code);		AMFProp_GetString(AMF_GetProp(&obj2, &av_level, -1), &level);		RTMP_Log(RTMP_LOGDEBUG, "%s, onStatus: %s", __FUNCTION__, code.av_val);						if (AVMATCH(&code, &av_NetStream_Failed)			|| AVMATCH(&code, &av_NetStream_Play_Failed)			|| AVMATCH(&code, &av_NetStream_Play_StreamNotFound)			|| AVMATCH(&code, &av_NetConnection_Connect_InvalidApp))		{			r->m_stream_id = -1;			RTMP_Close(r);			RTMP_Log(RTMP_LOGERROR, "Closing connection: %s", code.av_val);		}		// 判断播放是否成功		else if (AVMATCH(&code, &av_NetStream_Play_Start)			|| AVMATCH(&code, &av_NetStream_Play_PublishNotify))		{			int i;			r->m_bPlaying = TRUE;			for (i = 0; i < r->m_numCalls; i++)			{				if (AVMATCH(&r->m_methodCalls[i].name, &av_play))				{					AV_erase(r->m_methodCalls, &r->m_numCalls, i, TRUE);					break;				}			}		}		else if (AVMATCH(&code, &av_NetStream_Publish_Start))		{			int i;			r->m_bPlaying = TRUE;			for (i = 0; i < r->m_numCalls; i++)			{				if (AVMATCH(&r->m_methodCalls[i].name, &av_publish))				{					AV_erase(r->m_methodCalls, &r->m_numCalls, i, TRUE);					break;				}			}		}		/* Return 1 if this is a Play.Complete or Play.Stop */		else if (AVMATCH(&code, &av_NetStream_Play_Complete)			|| AVMATCH(&code, &av_NetStream_Play_Stop)			|| AVMATCH(&code, &av_NetStream_Play_UnpublishNotify))		{			RTMP_Close(r);			ret = 1;		}		else if (AVMATCH(&code, &av_NetStream_Seek_Notify))		{			r->m_read.flags &= ~RTMP_READ_SEEKING;		}		else if (AVMATCH(&code, &av_NetStream_Pause_Notify))		{			if (r->m_pausing == 1 || r->m_pausing == 2)			{				RTMP_SendPause(r, FALSE, r->m_pauseStamp);				r->m_pausing = 3;			}		}	}	// 删除无关代码***leave:	AMF_Reset(&obj);	return ret;}处理完上面的步骤之后，播放就可以开始了！