I am trying to build my own client RTMP library for an app that I am working on. So far everything has gone pretty successfully in that I am able to connect to the RTMP server negotiate the handshake and then send all the necessary packets (FCPublish Publish ETC) then from the server i get the onStatus message of NetStream.Publish.Start which means that I have successfully got the server to allow me to start publishing my live video broadcast. Wireshark also confirms that the information (/Data packetizing) is correct as it shows up correctly there also.
Now for where I am having some trouble is RTMP Chunking, going off the Adobe RTMP Specification on page 17 & 18 shows an example of how a message is chunked. From this example I can see that it is broken down based on the chunk size (128 bytes). For me the chunk size gets negotiated in the initial connect and exchange which is always 4096 bytes. So for when I am exchanging video data that is larger than 4096 bytes I need to chunk the message down sending the RTMP packetHeader combined with the first 4096 bytes of data then sending a small RTMP header which is 0xc4 (0xc0 | packetHeaderType (0x04)) combined with 4096 bytes of video data until the full packet specified by the header has been sent. Then a new frame comes in and the same process is repeated.
By checking other RTMP client example written in different languages this seems to be what they are all doing. Unfortunately the ingest server that I am trying to stream to is not picking up the broadcast video data, they dont close the connection on my they just never show video or any sign that the video is right. Wireshark shows that after the video atom packet is sent most packets sent are Unknown (0x0) for a little bit and then they will switch into Video Data and will sort of flip flop between showing Unknown (0x0) and Video Data. However if I restrict my payload max size to 20000 bytes Wireshark shows everything as Video Data. Obviously the ingest server will not show video in this situation as i am removing chunks of data for it to be only 20k bytes.
Trying to figure out what is going wrong I started another xcode project that allows me to spoof a RTMP server on my Lan so that I can see what the data looks like from libRTMP IOS as it comes into the server. Also with libRTMP I can make it log the packets it sends and they seem to inject the byte 0xc4 even 128 bytes even tho I have sent the Change Chunk size message as the server. When I try to replicate this in my RTMP client Library by just using a 128 chunk size even tho it has been set to 4096 bytes the server will close my connection on me. However if change libRTMP to try to go to the live RTMP server it still prints out within LibRTMP that it is sending packets in a chunk size of 128. And the server seems to be accepting it as video is showing up. When I do look at the data coming in on my RTMP server I can see that it is all their.
Anyone have any idea what could be going on?
While I haven't worked specifically with RTMP, I have worked with RTSP/RTP/RTCP pretty extensively, so, based on that experience and the bruises I picked up along the way, here are some random, possibly-applicable tips that might help/things to look for that might be causing an issue: