Bit-rate estimation is wrong for remuxed streams

[wmcbrine]

In the case of streams that are remuxed rather than reencoded, pyTivo still uses the pyTivo.conf-specified (or default) bitrate to estimate the final size. This is fine if the actual bitrate is lower (as indeed it is in most cases), although the TiVo may purge more old recordings than necessary. But if the actual bitrate is higher -- this happens primarily with Blu-Ray rips -- the size estimate will be too low, and the TiVo will delete the recording immediately.