HDTV Bitrates

[MarkGrigsby]

Hi,

Does anyone know (or have a link) how each of the main 4 US Networks broadcast their OTA HDTV? I know ABC & Fox use 720p, and CBS & NBC use 1080i - but how do their bitrates differ? I saw some captured shows, and seems Fox averages much smaller filesize for a 44 min drama, compared to the others!?

[edDV]

Hi,

Does anyone know (or have a link) how each of the main 4 US Networks broadcast their OTA HDTV? I know ABC & Fox use 720p, and CBS & NBC use 1080i - but how do their bitrates differ? I saw some captured shows, and seems Fox averages much smaller filesize for a 44 min drama, compared to the others!?

ABC 720p
CBS 1080i
FOX 720p or sometimes 480i (4:3), 480p (EDTV 16:9)
NBC 1080i
PBS 1080i or 480i/480p (EDTV-16:9) often
UPN 1080i
WB ?

Note: 720p and 1080i are always 16:9
Note: most of the day, these stations transmit upscaled 4:3 SDTV from NTSC.
Note: others note that the DTV service is in parallel to normal NTSC analog broadcasts.

Bandwidths vary locally. HDTV only would be 19Mb/s (1080i or 720p) but many stations also transmit a 480i SDTV channel (usually a conversion of their NTSC service) as well resulting in ~3-4Mb/s SDTV + 15-16Mb/s for HDTV.

Cable HD also varies locally by the condition of their cable infrastructure. Modern systems will use 20-25Mb/s, older systems will offer fewer channels and/or lower bitrates.

DBS is in the process of converting from miserable HD bitrates to an all new MPeg4 based 4-8Mb/s standard that will match OTA ATSC in quality with half the bandwidth per channel.

[MarkGrigsby]

Thanks! Is there any way to find out the bitrates of a particular local station? Also, I heard something about Fox being multiplexed differently to the others - does that make sense, or am I mis-remembering something?!

[edDV]

Thanks! Is there any way to find out the bitrates of a particular local station? Also, I heard something about Fox being multiplexed differently to the others - does that make sense, or am I mis-remembering something?!

Fox started their DTV service at 480p. Sports coverage introduced ABC type 720p60. Now most national FOX HD is 720p just like ABC.

[Robert Simandl]

But oddly enough, Fox's bitrate (assuming this week's Prison Break is typical) is only 9.5mbps... a one hour episode actually fits on a DVD-R once the commercials are removed, though the 1280x720 resolution would cause an error message on a standard DVD player.

This is with no subchannels on a Fox O&O station.

[edDV]

But oddly enough, Fox's bitrate (assuming this week's Prison Break is typical) is only 9.5mbps... a one hour episode actually fits on a DVD-R once the commercials are removed, though the 1280x720 resolution would cause an error message on a standard DVD player.

This is with no subchannels on a Fox O&O station.

Individual TV stations are free to do what they want with bitrate. Minimum DTV requirement is to send one SD signal on the n.1 channel @ ~2-6Mb/s. The rest of the 19Mb/s could be used to send additional channels or even data if they wish.

[Epicurus8a]

Thanks! Is there any way to find out the bitrates of a particular local station? Also, I heard something about Fox being multiplexed differently to the others - does that make sense, or am I mis-remembering something?!

Call your local station during regular business hours and ask for the 'Chief Engineer' or 'Director of Engineering.'