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RTMPdump(libRTMP) 源代码分析系列文章:
RTMPdump 源代码分析 1: main()函数
RTMPDump (libRTMP) 源代码分析2:解析RTMP地址——RTMP_ParseURL()
RTMPdump (libRTMP) 源代码分析3: AMF编码
RTMPdump (libRTMP) 源代码分析4: 连接第一步——握手 (HandShake)
RTMPdump (libRTMP) 源代码分析5: 建立一个流媒体连接 (NetConnection部分)
RTMPdump (libRTMP) 源代码分析6: 建立一个流媒体连接 (NetStream部分 1)
RTMPdump (libRTMP) 源代码分析7: 建立一个流媒体连接 (NetStream部分 2)
RTMPdump (libRTMP) 源代码分析8: 发送消息 (Message)
RTMPdump (libRTMP) 源代码分析9: 接收消息 (Message) (接收视音频数据)
RTMPdump (libRTMP) 源代码分析10: 处理各种消息 (Message)
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函数调用结构图
RTMPDump (libRTMP)的整体的函数调用结构图如下图所示。
单击查看大图
详细分析
前文已经分析了 RTMPdump中建立一个NetConnection的过程:RTMPdump 源代码分析 5: 建立一个流媒体连接 (NetConnection部分)
多余的话不多说,下面先来看看RTMP_ConnectStream(),该函数主要用于在NetConnection基础上建立一个NetStream。
RTMP_ConnectStream()
-
- int
- RTMP_ConnectStream(RTMP *r, int seekTime)
- {
- RTMPPacket packet = { 0 };
-
-
-
-
- if (seekTime > 0)
- r->Link.seekTime = seekTime;
-
- r->m_mediaChannel = 0;
-
- while (!r->m_bPlaying && RTMP_IsConnected(r) && RTMP_ReadPacket(r, &packet))
- {
- if (RTMPPacket_IsReady(&packet))
- {
- if (!packet.m_nBodySize)
- continue;
- if ((packet.m_packetType == RTMP_PACKET_TYPE_AUDIO) ||
- (packet.m_packetType == RTMP_PACKET_TYPE_VIDEO) ||
- (packet.m_packetType == RTMP_PACKET_TYPE_INFO))
- {
- RTMP_Log(RTMP_LOGWARNING, "Received FLV packet before play()! Ignoring.");
- RTMPPacket_Free(&packet);
- continue;
- }
-
-
- r->dlg->AppendCInfo("建立网络流:处理收到的数据。开始处理收到的数据");
-
- RTMP_ClientPacket(r, &packet);
-
- r->dlg->AppendCInfo("建立网络流:处理收到的数据。处理完毕,清除数据。");
-
- RTMPPacket_Free(&packet);
- }
- }
-
- return r->m_bPlaying;
- }
乍一看,这个函数的代码量好像挺少的,实际上不然,其复杂度还是挺高的。我觉得比RTMP_Connect()要复杂不少。其关键就在于这个While()循环。首先,循环的三个条件都满足,就能进行循环。只有出错或者建立网络流(NetStream)的步骤完成后,才能跳出循环。
在这个函数中有两个函数尤为重要:
RTMP_ReadPacket()
RTMP_ClientPacket()
第一个函数的作用是读取通过Socket接收下来的消息(Message)包,但是不做任何处理。第二个函数则是处理消息(Message),并做出响应。这两个函数结合,就可以完成接收消息然后响应消息的步骤。
下面来开一下RTMP_ReadPacket():
-
- int
- RTMP_ReadPacket(RTMP *r, RTMPPacket *packet)
- {
-
-
- uint8_t hbuf[RTMP_MAX_HEADER_SIZE] = { 0 };
-
- char *header = (char *)hbuf;
- int nSize, hSize, nToRead, nChunk;
- int didAlloc = FALSE;
-
- RTMP_Log(RTMP_LOGDEBUG2, "%s: fd=%d", __FUNCTION__, r->m_sb.sb_socket);
-
- if (ReadN(r, (char *)hbuf, 1) == 0)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read RTMP packet header", __FUNCTION__);
- return FALSE;
- }
-
- packet->m_headerType = (hbuf[0] & 0xc0) >> 6;
-
- packet->m_nChannel = (hbuf[0] & 0x3f);
- header++;
-
- if (packet->m_nChannel == 0)
- {
- if (ReadN(r, (char *)&hbuf[1], 1) != 1)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read RTMP packet header 2nd byte",
- __FUNCTION__);
- return FALSE;
- }
-
- packet->m_nChannel = hbuf[1];
- packet->m_nChannel += 64;
- header++;
- }
-
- else if (packet->m_nChannel == 1)
- {
- int tmp;
- if (ReadN(r, (char *)&hbuf[1], 2) != 2)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read RTMP packet header 3nd byte",
- __FUNCTION__);
- return FALSE;
- }
- tmp = (hbuf[2] << 8) + hbuf[1];
-
- packet->m_nChannel = tmp + 64;
- RTMP_Log(RTMP_LOGDEBUG, "%s, m_nChannel: %0x", __FUNCTION__, packet->m_nChannel);
- header += 2;
- }
-
- nSize = packetSize[packet->m_headerType];
-
- if (nSize == RTMP_LARGE_HEADER_SIZE)
- packet->m_hasAbsTimestamp = TRUE;
-
- else if (nSize < RTMP_LARGE_HEADER_SIZE)
- {
- if (r->m_vecChannelsIn[packet->m_nChannel])
- memcpy(packet, r->m_vecChannelsIn[packet->m_nChannel],
- sizeof(RTMPPacket));
- }
-
- nSize--;
-
- if (nSize > 0 && ReadN(r, header, nSize) != nSize)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read RTMP packet header. type: %x",
- __FUNCTION__, (unsigned int)hbuf[0]);
- return FALSE;
- }
-
- hSize = nSize + (header - (char *)hbuf);
-
- if (nSize >= 3)
- {
-
- packet->m_nTimeStamp = AMF_DecodeInt24(header);
-
-
-
- if (nSize >= 6)
- {
- packet->m_nBodySize = AMF_DecodeInt24(header + 3);
- packet->m_nBytesRead = 0;
- RTMPPacket_Free(packet);
-
- if (nSize > 6)
- {
-
- packet->m_packetType = header[6];
-
- if (nSize == 11)
- packet->m_nInfoField2 = DecodeInt32LE(header + 7);
- }
- }
-
- if (packet->m_nTimeStamp == 0xffffff)
- {
- if (ReadN(r, header + nSize, 4) != 4)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read extended timestamp",
- __FUNCTION__);
- return FALSE;
- }
- packet->m_nTimeStamp = AMF_DecodeInt32(header + nSize);
- hSize += 4;
- }
- }
-
- RTMP_LogHexString(RTMP_LOGDEBUG2, (uint8_t *)hbuf, hSize);
-
- if (packet->m_nBodySize > 0 && packet->m_body == NULL)
- {
- if (!RTMPPacket_Alloc(packet, packet->m_nBodySize))
- {
- RTMP_Log(RTMP_LOGDEBUG, "%s, failed to allocate packet", __FUNCTION__);
- return FALSE;
- }
- didAlloc = TRUE;
- packet->m_headerType = (hbuf[0] & 0xc0) >> 6;
- }
-
- nToRead = packet->m_nBodySize - packet->m_nBytesRead;
- nChunk = r->m_inChunkSize;
- if (nToRead < nChunk)
- nChunk = nToRead;
-
-
- if (packet->m_chunk)
- {
- packet->m_chunk->c_headerSize = hSize;
- memcpy(packet->m_chunk->c_header, hbuf, hSize);
- packet->m_chunk->c_chunk = packet->m_body + packet->m_nBytesRead;
- packet->m_chunk->c_chunkSize = nChunk;
- }
-
- if (ReadN(r, packet->m_body + packet->m_nBytesRead, nChunk) != nChunk)
- {
- RTMP_Log(RTMP_LOGERROR, "%s, failed to read RTMP packet body. len: %lu",
- __FUNCTION__, packet->m_nBodySize);
- return FALSE;
- }
-
- RTMP_LogHexString(RTMP_LOGDEBUG2, (uint8_t *)packet->m_body + packet->m_nBytesRead, nChunk);
-
- packet->m_nBytesRead += nChunk;
-
-
- if (!r->m_vecChannelsIn[packet->m_nChannel])
- r->m_vecChannelsIn[packet->m_nChannel] = (RTMPPacket *) malloc(sizeof(RTMPPacket));
- memcpy(r->m_vecChannelsIn[packet->m_nChannel], packet, sizeof(RTMPPacket));
-
- if (RTMPPacket_IsReady(packet))
- {
-
- if (!packet->m_hasAbsTimestamp)
- packet->m_nTimeStamp += r->m_channelTimestamp[packet->m_nChannel];
-
- r->m_channelTimestamp[packet->m_nChannel] = packet->m_nTimeStamp;
-
-
-
- r->m_vecChannelsIn[packet->m_nChannel]->m_body = NULL;
- r->m_vecChannelsIn[packet->m_nChannel]->m_nBytesRead = 0;
- r->m_vecChannelsIn[packet->m_nChannel]->m_hasAbsTimestamp = FALSE;
- }
- else
- {
- packet->m_body = NULL;
- }
-
- return TRUE;
- }
在这里要注意的是,接收下来的实际上是块(Chunk)而不是消息(Message),因为消息(Message)在网络上传播的时候,实际上要分割成块(Chunk)。这里解析的就是块(Chunk)
可参考:RTMP规范简单分析
具体的解析代码我就不多说了,直接参考RTMP协议规范就可以了,一个字节一个字节的解析就OK了。
rtmpdump源代码(Linux):http://download.csdn.net/detail/leixiaohua1020/6376561
rtmpdump源代码(VC 2005 工程):http://download.csdn.net/detail/leixiaohua1020/6563163