[mythtv-users] HDTV - PVR: Does it work?

[Jarod C. Wilson]

On Jan 20, 2004, at 22:45, Ian Forde wrote:

> On Tue, 2004-01-20 at 20:37, Brandon Beattie wrote:
>> 1080i is the highest bandwidth HDTV stream at 19.6Mb/s.  A full ATSC
>> stream can be up to 45Mb/s but this is only if you save all the
>> subchannels(Which would have to be maxed out)  Most atsc streams are
>> 14-25Mb/s that I see on my 11 HD stations.  The HDTV streams come
>> through as transport streams (MPEG2-TS) which contain redundant
>> information for i frames in the mpeg codec just incase some data is 
>> lost
>> in transmission.  Douglas and others have already taken a few steps to
>> remove this and turn the mpeg2-ts into mpeg2-ps (No redundant data 
>> such
>> as used for DVD's).  This cuts off some useless bandwidth once the
>> stream is received.  (About 10-20% with little CPU usage).  So the end
>> answer is you shouldn't push more than about 20-25Mb/s from the 
>> backend
>> to the frontend for watching a HD show.  a 100Mb/s connection is 
>> plenty.
>
> Uhhh... 20-25MB/s is impossible on 100Mb.  Even 100 FullDuplex...

Ah yes Ian, 20-25MB/s is impossible, but Brandon said 20-25Mb/s. ;-)

> 100 Megabits = around 12MB/sec fully utilized.  I've never seen more
> than 11MB/sec.  And that was with a crossover cable...

And 20-25Mb/s is around 3-4MB/s, for anyone else that was wondering. 
1MB/s is 8Mbps, 12.5MB/s is 100Mbps, etc. (8 bits = 1 Byte). I see a 
max of about 8.7MB/s (about 70Mbps) on a 100Mbps switched network here, 
so no problems streaming HD from machine to machine. Just beware of 
bottlenecks if you have multiple switches and/or hubs in the mix. Also, 
some NICs perform like absolute crap under Linux, and won't push much 
more than 6.5MB/s on the same network I usually get 8+ on. 
Unsurprisingly enough, most of the crappy throughput ones are the cheap 
ones.

GigE is nice. I just got a GigE switch and a Linksys Instant Gigabit 
network adapter for my file server. The only other GigE device (so far) 
is my Mac, but HOT DAMN! the speed between the two is zippy. No HD 
bottleneck issues there! =]

-- 
Jarod C. Wilson, RHCE

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