[mythtv-users] Way out idea on watching same thing in multiplerooms

Tortise tortise at paradise.net.nz
Tue Jan 5 19:09:56 UTC 2010


----- Original Message ----- 
From: Gareth Glaccum
To: Discussion about mythtv
Sent: Wednesday, January 06, 2010 2:29 AM
Subject: Re: [mythtv-users] Way out idea on watching same thing in multiplerooms


From: Charles Wright <cpwright at gmail.com>
>On Tue, Jan 5, 2010 at 5:33 AM, Gareth Glaccum
>> 2) I am a data-stream (video), how do I get where I am going?
>> In an ideal world, multicast would be great.

>One could also just use unicast instead of multicast or unicast.  If
>you've got an HD stream, I think it should be about 7GB/hour which
>works out to ~15.5Mbps.  Multiply that by 5 front-ends (seems like
>reasonable number for most homes) and you've got 77Mbps, which is
>still far under 1Gbps and you aren't going to affect devices which
>aren't using the stream.

>Yup, I agree with that in principle. What about if they only have a 100mb/s switch or hub though?

>However, I think that whatever is put in place, should be done with the idea that sometime in the future, multicast could be 
>implemented /safely/ and an 'upgrade' to multicast should be coded in easily.
_______________________________________________

Add in one more FE, a bit of VOIP and some file downloads and I can see a "1G" LAN intermittently falling over at those levels for 
VOIP and Video.  "1G" LANs are in my experience much less than 1G.  I've not yet seen a 1G NIC get anything near that through it. 
Even 100M would raise my eyebrows.

While "10G" networks are coming around home network gear tends to lag and not lead in available capability.

Chris Pinkham early in this thread described an alternative method to achieve a similar thing.  I think multicast and Chris's method 
both have good and bad points.

Wired network latency seems irrelevant.  Wireless is well known to have problems with multicast which will be relevant for some.  (I 
personally try to avoid wireless as much as possible - this is just another reason why.)

Would Chris's method avoid different length frontend buffers?  If I start a bookmarked recording there also seems to be a buffering 
("Wait please...") pause, certainly a start pause, in that respect it may have little advantage?  Synchronisation is a good idea, 
would it work smoothly on slave frontends?

Which method would be better?  The answer may be related to the number of frontends - the more there are the better multicast looks. 
If one is making a scalable piece of kit, instead of doing it unicast - then lateron revising it for multicast, would it be better 
to just do it with multicast? 



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