Video playback is a function of many dependencies in a chain. If any one of them is a weak link, then perormance will suffer. Upload speed is very important. So is download speed.
If you're transcoding at 5000kbps or 5Mbps then to keep up with the servers output you have to have at least 5Mbps upload speed and no other traffic taking away bandwidth. I always find you need to overestimate these things a bit, so for 5000kbps you really want about 10Mbps service going out.
Assuming that your getting the data out, you need to recieve it at the other end with comparable download speed.
In the early days of testing video playback I would travel about 400 miles away from home to visit relatives. They had reasonably good internet connection and I was able to get pretty good results. I then found that I would get different results depending on the playback hardware I was using. An older laptop with an older graphics card would buffer while a newer laptop would play just fine with no buffering. Both were using the same connection.
In most environments today you're seldom alone on the network. Any traffic bottleneck anywhere can foul things up. That's why hardware horsepower is so important whentranscoding and playing back video. A strong server on a gigabit lan connection with great internet service is a big plus. Even then if the other end only has 5Mbps service at the recieving end there can be buffering depending on how many hops it takes to get to the connection.
I have 35/35 Mbps FIOS internet service that consistently (we're talking anytime I test it consistent) tests at 43Mbps down and 35Mbps up. Even still I go on youtube and get buffering while playing youtube vids. I'm pretty sure they have some strong resources, so I don't think it's reasonable to expect that I'm going to do consistently better. Video is very demanding on CPU and bandwidth resources. Anything that isn't optimal can cause playback disruption.
I'll send you a link to my site so you can see how well it does at your end. I'm running a dual quad core Xeon sever, 16GB ram, dual gigabit NICS teamed, and FIOS internet. It's probably about as good as you'll see unless someone else has better upload speed, as I suspect that my upload speed is the slowest part of the chain and should handle the 5Mbps output without problems. Also test some mp4 files as they aren't transcoded. Select the videos folder and try different formats.
HTH
