a lot of minor-mss packets in tcpdump

I have a situation where I am running Vine on Mac and client is Flashlight running on Ubuntu 12.04. The latency is about 500ms and the performance was not so good so I took a tcpdump to see what is going on.
I see that there are a lot of minor-mss packets in the stream. Why would this happen? The tcp window is always significantly more than the data that is being sent by the server. Is there some sort of optimization or or anything that is being done at the server level because of which this is happening?

There aren’t any specific TCP optimizations that I am aware of but all the source for Vine Server is available on SourceForge:

There is a buffering mechanism in the frame buffer data transfer, perhaps that’s what you are seeing.