A good rule of thumb is to encode only 50-60% of your upload bandwidth capacity for the BoxCaster. You can utilize an online tool such as http://www.speedtest.net/ to see your upload and download bandwidth capabilities. In general, we recommend having at least 1.5Mbps of upload to consider streaming. Anything less than that and you run the risk of disruptions affecting the quality of your stream.
For example, if you have 2Mbps of upload speed available, your combined audio and video bitrate should not exceed 1Mbps. To stream in HD, you'll want at least 2.5 - 3Mbps upload speed available.