Originally posted by wareagle
Will the SD programs broadcast on the HD channels require the same disk space as HD?
Depends upon how it's encoded. If it's constant bit rate, then yes they could broadcast a black screen with no audio for the entire duration of the program and it would still take the same amount of bandwidth as something active. If it's variable bit rate, and it's a 4:3 aspect ratio program (which hasn't been stretched/zoomed), that leaves about ¼ of the picture area unused, which could theoretically allow the encoder to scale the bitrate back a bit (or else provide a better quality picture on that which is
active), but not by much. However, if it's a widescreen SD source (or stretched/zoomed), that SD picture has been upconverted to HD and has as many pixels assigned to it as true HD would, so it would take just as much bandwidth.
Originally posted by WiFi-Spy
I have heard INHD 1&2 and DHDT and I think ESPN have the highest bitrates (like 30Mbs+)
while the locals have around 20Mbs.....
The maximum ATSC-spec bitrate is 19.363mbps, and on a 256QAM channel, there's just enough room for 2 at that bitrate. 30+mbps would only allow one HD channel per QAM channel, which would be no better use of bandwidth than analog.