[mythtv-users] Multicasting BE Recordings - now can do!

[Nick Rout]

On Mon, Jan 11, 2010 at 2:58 PM, Tortise <tortise at paradise.net.nz> wrote:
> ----- Original Message ----- From: "Nick Rout" <nick.rout at gmail.com>
> To: "Discussion about mythtv" <mythtv-users at mythtv.org>
> Sent: Monday, December 14, 2009 8:54 PM
> Subject: Re: [mythtv-users] Any FE to Many PCs - LAN Content Simulcasts
> withVLC Multicasting
>
>
> On Sun, Dec 13, 2009 at 12:05 PM, Tortise <tortise at paradise.net.nz> wrote:
>>
>> GOAL: Move to integrate HD into an Any to Many Model.
>>
>> I've been trying to achieve "any FE PC to many PC simulcasts of live and
>> recorded content" for some time in the new HD world.
>>
>> I have enjoyed this for some time in the SD World using a dual channel
>> modulator that puts out a UHF Channel stream as taken from a
>> SD AV receiver composite output feed as also displayed on the respective
>> TV's (used effectively just as Monitors) one in the Lounge
>> and
>> the 2nd in my room where this kit resides. That old world is therefore a 2
>> to many situation which was ok, any to many would be
>> even better, especially as I
>> move to have a PC in most rooms.
>>
>> Why do this? The typical TV program model is to sit down in one room and
>> watch the one screen. Sometimes I like to watch something
>> on the move between a number of rooms - a good example might be in the
>> early
>> evenings I might want to watch something, cook some
>> stuff and work on something in the workshop - roaming between those rooms.
>>
>> With the SD model that was cool, a quick flick on of the (old!) TV in each
>> room and tune the respective channel UHF and the stream
>> is replicated, be it live tv, tivo, mythtv, dvd, radio, whatever....
>>
>> And HD? Not so easy! Some ways to do this have occurred to me:
>>
>> Coaxial Transmission:
>> HD Modulator
>> If there was an economic HD modulator equivalent I'd also need HD tuners
>> in
>> each location. Not so good an idea.
>>
>> Existing SD Modulators
>> To achieve this I need to descale the HD video to SD, which can then be
>> fed
>> into the existing network. Quality descaling would
>> result in a quality SD experience in most rooms, this would be acceptable.
>> 16:9 HD would potentially be seen on both 4:3 SD TV's
>> and 16:9 HD TV's. But getting SD from HD from each myth box? Not so easy.
>> The myth boxes that I am more likely to want to see
>> broadcast locally feed their displays with component. Hmmm.
>> I could use a VGA in / Component and Composite Out box however the quality
>> of this conversion seems somewhat risky, one would be
>> required from each set of Mythtv
>>
>> MultiCast with VLC:
>> This might work, I figure I'd use VLC as the myth media player and set it
>> to
>> multicast at the same time using the appropriate
>> command line. Then any PC on the network could tune the appropriate
>> multicast stream...any pc...and bingo, multicast! Each
>> multicast client would need to have enough puff to play the HD streams.
>> (This means they need to be higher spec CPU's as can't use
>> vdpau) I've tested VLC multicast and it works well out of the box. Now I
>> just need to set it up...and test some more.... Anyone
>> thought of this, tried this or any comments?
>>
>
>> mythtv is a upnp server
>> vlc can act as a upnp client
>> vlc can act as a multicast server
>
>> solution: find a mechanism to star vlc as a upnp client to the
>> mythbackend, and simultaneously multicast it to your lan.
>
> Well that didn't work as uPnP was missing....  until today...
>
> The latest VLC update (I think via
> http://ppa.launchpad.net/mythbuntu/repos/ubuntu) just added in uPnP support.
>
> It reads my mythtv BE via uPnP but seems to crash playing stuff.....every
> step is small....!
>
> However.......if I click stream........it streams a recording direct from
> the mythBE...and plays it also!! All be it with an incorrect aspect ratio on
> the server(!)  Setting aspect ratio to 16:9 seems to fix this.
>
> Clients are correct in their aspect ratio.
>
> CPU with a 576i H264 stream is about 30-40%.  (3.16G C2D)
>
> Great idea Nick thanks.  (Anyone want to check out audio sync / echo issues
> on recordings easily can now...)
>
> Kewl!

We seem to have switched threads again. However it seems to me that
the summary, mainly of the other thread, is:

1. multicasting is the way to go but cheap consumer switches might
create a heavier network usage by broadcasting to nodes that don't in
fact want to take part; and

2. multicasting should work fine to broadcast to a number of frontends
if you don't care about precise synchronisation; but

3. precise synchronisation to  the level required to not annoy the
ears would be difficult but not impossible (linuxmce claims to do it
for video, squeezebox server does it for audio); and

4. control of pausing etc would not be achieved by simple
multicasting, but some sort of control could be incorporated, probably
along the line of a 'master frontend' (which function may be able to
be moved from frontend to frontend); and

5. until a control mechanism is implemented it will be more like an
old fashioned TV broadcast.