[mythtv-users] how much space does an HD recording take?

Brandon Beattie brandon+myth at linuxis.us
Tue May 10 14:23:49 UTC 2005


On Tue, May 10, 2005 at 07:50:43AM -0400, Anthony Vito wrote:
> > Shows can be more than
> > 19.6Mb/s when they have multiple audio subchannels.  
> 
> I call bullshit!! 8VSB at 6Mhz is limited to 19.39Mbps for the _full_
> transport layer. That includes all video and audio channels. If you
> want more audio channels, you have to give up some video bandwidth.
> 
> http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

Oh the language.. I am wrong from time to time, but not this time. :)  

It is true you can't go over your RF bandwidth...  But who said the RF
bandwidth was 19.39Mb/s?.. because it surely is not.  ATSC is a 45Mb/s
RF data stream.  If a channel were sending a 1080i stream (19.39Mb/s),
then how could they ever send other video sub channels?  (And don't say
they cut their video bandwidth of the 1080i stream.. ;)  However a
station wants to fill their 45Mb/s stream is up to them.  2 1080i and 1
480p stream, 3 720p streams, 1 1080i and 1 480p, or 1 480i stream... it
doesn't matter, and many stations have unused bandwidth.  

Yes broadcast uses 8VSB at 6mhz, but it's on 45Mb/s, not 19.39Mb/s.  One
area I do need to still research is if the 19.39 includes or does not
include the redundant packets for error correction.

--Brandon


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