[Live-devel] Video quality at the client

[Ross Finlayson]

> I have the RTSP server stood up and working pretty well, my only issue now is that the video that is being received by the client is pixelated pretty badly.  It is worse when using RTSP over UDP, but it is still bad over TCP.  I am using VLC as a client and when the server and client are run locally this issue does not seem to exist.

Because of this, the problem is probably due to insufficient network bandwidth between your server and client.


>   I thought that switching to TCP (for more reliable delivery) this issue would be resolved

TCP gives you reliable delivery between the server's OS and the client's OS.  However, the server *application* - i.e. the thing that is generating the video stream - is generating data at a certain rate.  If this rate exceeds the capacity of the network, then you will still get data loss - at the point where the server application feeds the server OS.  I.e., you will get data loss because the server's TCP buffer(s) will fill up, and then the server application's socket writes will start failing.  This is how live media streaming differs from downloading a file (e.g., from a web server).  When you're downloading a file, the file transfer takes place at the underlying speed of the network.  That's not the case for live media streaming.

In other words: It's important to understand that streaming RTP-over-TCP is not a panacea.  If your media stream exceeds the capacity of the network, then you *will* get data loss, no matter what.  Streaming RTP-over-TCP just moves that data loss from the network back to the server.


>   Any suggestions on fixing this issue?

You either need a faster network, or else you need to reduce the bandwidth of your video stream (by reducing the frame rate, and/or the video resolution).


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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