rtmp之csid 乱谈

从标准中，我们可以看到，protocol control message的csid要设置成2，msid要设置成0

但是其他的message csid要设置多少，从srs中找到了一些蛛丝马迹

channel id 或 chunk stream id 定义
详细的英文描述见 srs/trunk/src/kernel/srs_kernel_flv.hpp
SRS是参考FMS定义的。


/**
 * the chunk stream id used for some under-layer message,
 * for example, the PC(protocol control) message.
 */
#define RTMP_CID_ProtocolControl 0x02
/**
 * the AMF0/AMF3 command message, invoke method and return the result, over NetConnection.
 * generally use 0x03.
 */
#define RTMP_CID_OverConnection 0x03
/**
 * the AMF0/AMF3 command message, invoke method and return the result, over NetConnection,
 * the midst state(we guess).
 * rarely used, e.g. onStatus(NetStream.Play.Reset).
 */
#define RTMP_CID_OverConnection2 0x04
/**
 * the stream message(amf0/amf3), over NetStream.
 * generally use 0x05.
 */
#define RTMP_CID_OverStream 0x05
/**
 * the stream message(amf0/amf3), over NetStream, the midst state(we guess).
 * rarely used, e.g. play("mp4:mystram.f4v")
 */
#define RTMP_CID_OverStream2 0x08
/**
 * the stream message(video), over NetStream
 * generally use 0x06.
 */
#define RTMP_CID_Video 0x06
/**
 * the stream message(audio), over NetStream.
 * generally use 0x07.
 */
#define RTMP_CID_Audio 0x07