I have now a proof for my theory of a workaround.
In my setup, no matter how I configure the buffer size, the FTP would always be much faster than the decoding on the TV, so in the end there is buffer underrun and decoding finishes too early.
My theory of a workaround was to limit the FTP transfer rate.
My solution is to limit the FTP transfer rate ON THE PC.
There is a Windows program "NetLimiter 4" which you can google and download.
With this program, it is possible to limit the TCP/IP DL or UL speeds of particular programs.
With a limit of PVRDecoder Download speed to 4 MB/s (which results in decoding speed of 32 Mbit/s on the TV), everything works well on my setup!



If you would find a way to limit the FTP transfer rate within SamyGo PVRDecoder itself, this would be the solution. In particular since you KNOW the actual decoding rate on the TV (since it is printed while it decodes), there could even be an easy solution to auto-configure the limiting of the FTP transfer rate.