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<DIV><FONT face=Arial size=2>The question I have, is how does the frontend
actually play the data? I am here watching mythtv player on my MS windows
machine.</FONT><FONT face=Arial size=2> I am watching CSI whilst the
backend/frontend machine behind me is recording and playing CSI at the same
time. I synchronised the two by very careful pause/unpause, but that is of no
consequence. </FONT></DIV>
<DIV><FONT face=Arial size=2>Basically, my windows box knows nothing about the
nfs mount. The frontend, does have the data locally, but perhaps it is receiving
the same IP stream as the mythtv player? If this is the case, then this is a
serious waste of bandwidth. So how to get around this? Multicasting the data
from the backend to the frontends. This would be a 'perfect' solution. The
information that the frontends require to play the audio and video is the same
data, therefore, if the frontends are capable of decoding and playing the data
in realtime, they have to be synchronised because they are playing exactly the
same data.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Unfortunately this is a problem for more than one
reason.</FONT></DIV>
<DIV><FONT face=Arial size=2>1) Probably requires a bit of a nasty wire change.
I would suspect the easiest way of implementing it would be to move the video
and audio out to a completely seperate stream. This new stream would be
multicast. The 'old' ports etc. would still be used, for frontends to control
which streams are being broadcast and to state that they are joining and
leaving. </FONT></DIV>
<DIV><FONT face=Arial size=2>2) Will cause pain for a lot of people. There are
several well-known switch manufacturers who have not implemented multicasting
properly. For most applications this is not an issue. Unfortunately for us, the
problems usually arise when there is a lot of data transfer. The stream I am
watching is 218kb/s, not that much I suppose, but it would be enough to toast a
badly written switch. The trouble with these dodgy switches is that they appear
to work for a while, then become intermittent. </FONT></DIV>
<DIV><FONT face=Arial size=2>3) What happens if one frontend decides to pause,
but the user at another frontend decides it doesn't want to? Some thought into
how much control you have over the other frontends is required.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Personally I think that I would use this quite a
lot. However, is there enough interest behind this to implement? Implementation
of this is surely not beyond the writers, they have done a great job already,
but it does require a significant change to the way the system works I think.
Now apparently there is plans to support multicast recording in mythtv 0.21,
perlhaps someone is thinking of this already?</FONT></DIV>
<DIV><FONT face=Arial size=2>Gareth</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=mattasplund@gmail.com href="mailto:mattasplund@gmail.com">Matthew
Asplund</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=mythtv-users@mythtv.org
href="mailto:mythtv-users@mythtv.org">Discussion about mythtv</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, January 16, 2007 1:20
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [mythtv-users] Duplicate
screens</DIV>
<DIV><BR></DIV>Actually, how about an option under the "Media Library" or
"Watch TV" menu that would be "Synchronize to another Myth Front-End".
You could then choose which front-end from all front-ends that are connected
to your back-end. The slave front-end would then do whatever the master
front-end does. Given that I can sync the time on my computers using
NTP, it would be enough to send the occasional time marker command to keep
them together. In practice, it would be great if they were within 10 ms,
to minimize the echo , which is pretty easy even for a ping command.
<BR><BR>Now the one tricky part that I can see, is what if you have one SD
setup and one HD setup. I suppose that if you are using SD content it is
easy, and if you have HD content, then the SD front-end is responsible for
rendering the stream into 480p to make it work out.
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