Sean Carolan wrote:
For a back-of-the napkin calculation can we not assume that data equal to the entire size of the file will be streamed to the client during playback?
You can if you're using some of the fudge factors others have mentioned here. The headers for IP + UDP + RTP take at least 3.5% of the bandwidth for a network using a PMTU of 1500 bytes. If the smallest MTU between your system and the receiver is smaller, the percentage goes up. And, the percentage goes up anyway because those numbers only talk about the minimum overhead. RTP headers are flexible, as are most higher-level protocols, like TCP.
We're also ignoring any other traffic on the link. With RTP, for instance, there are usually RTCP and RTSP channels as well. Without these parallel data channels, the stream doesn't work.
You also have to account for retries and buffering. If your network link is exactly as big as it has to be for the ideal case, you will still have problems because the time it takes to deal with lost or damaged packets comes out of your bit rate budget. There's a limit to the effectiveness of prebuffering.
10% total overhead isn't unreasonable.