SD/HD Tivo Audio/Video/Codec compatibility validation

SD/HD Tivo Audio/Video/Codec compatibility validation

MPEG AUDIO COMPATIBILITY:
Converts user provided audio bitrates to non-zero multiple
of 64 for ffmpeg compatiblity.
Sets max audio bitrate to 384k/448k for S2/S3 tivos respectively.
Checks audio bitrate of source and transcodes if max audio bitrate exceeded.
Compares audio_br and max_audio_br and uses the lower of the
two bitrates to ensure a tivo compatible bitrate is used.
MAX_AUDIO_BR may be specified in conf to override defaults.
MAX_AUDIO_BR is both a 'Server' and 'Per Tivo' option.

MPEG VIDEO COMPATIBILITY:
Expands use of existing setting MAX_VIDEO_BR=17408K.
Checks VIDEO bitrate of source and transcodes if max video bitrate exceeded.
MAX_VIDEO_BR may be specified in conf to override default.
MAX_VIDEO_BR is a 'Server' option.

TIVO AUDIO CODEC COMPATIBILITY:
Checks for HD tivo and uses ac3 audio automatically so that
5.1 audio is retained if present in the source.
Otherwise, mp2 audio is used for S2 compatibility.
User may still override by specifying their own ffmpeg template.

hdtivosonly=true
New option for 'Server' section.
Allows HD ONLY users to quickly tell pyTivo to use all
default settings for HD tivos rather than add multiple
per Tivo sections.