After the streaming tests, I repeated my experiments using the file play method and found quite different results. As might be expected due to TCP/IP's tenacity at fixing transmission errors, I found it much harder to get the video to break up. And when it did falter, the problem was more likely to be pauses and skips than compression artefacts such as blockiness.

I had to resort to introducing uniformly distributed delay as well as packet loss to reliably get the video to fail. With 1% packet loss and delay between 10 and 500 ms, the VOB file suffered frequent stutters and pauses and eventually locked up after a few minutes. When I tried the same settings with the same file encoded with DivX using its Home Theatre Quality setting, I encountered less frequent stutters and pauses and the file didn't lock up.

My general conclusions from the file play tests are:

Files played across a network using TCP/IP are much more resistant to packet loss errors bit rate and encoding format can make a difference in a played file's susceptibility to transmission errors

Conclusions

I was surprised at how little packet loss it took to affect video streaming, and just as surprised at how hard it was to disturb files played using TCP/IP based protocols. In Part 2 of this NTK, I'll put this knowledge to work with wireless LANs to see what works and what doesn't for successful video streaming.

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