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jerome at supernet

Apr 11, 2012, 6:35 PM

Post #1 of 26 (2224 views)
Permalink
simultaneous viewing

Does anyone use VNC to have more than one machine display content from
MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
between. I don't care about sound from the kitchen - I can turn up volume
on the main machine, but video would be good as long as it doesn't lag
badly. It's the start of hockey playoffs, and I record 3 or 4 games a
night, and a guy's gotta eat!
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raymond at wagnerrp

Apr 11, 2012, 6:45 PM

Post #2 of 26 (2201 views)
Permalink
Re: simultaneous viewing [In reply to]

On 4/11/2012 21:35, Jerome Yuzyk wrote:
> Does anyone use VNC to have more than one machine display content from
> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
> between. I don't care about sound from the kitchen - I can turn up volume
> on the main machine, but video would be good as long as it doesn't lag
> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
> night, and a guy's gotta eat!

Are you asking if you can use VLC to stream video? If so, no.
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coronasensei at gmail

Apr 11, 2012, 6:56 PM

Post #3 of 26 (2200 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12/04/12 11:45, Raymond Wagner wrote:
> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>> Does anyone use VNC to have more than one machine display content from
>> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
>> between. I don't care about sound from the kitchen - I can turn up
>> volume
>> on the main machine, but video would be good as long as it doesn't lag
>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>> night, and a guy's gotta eat!
>
> Are you asking if you can use VLC to stream video? If so, no.
>
No, he's asking about VNC, not vlc.
I've used VNC to remote admin my main box at times, basically as a
wireless keyboard.

The video does come through, but _very_ low framerate on wifi. It's
worth a try though on gigabit, might work. May also have to look into
settings regarding refresh rate, try to manually get that as high /
higher than the frame rate of your content.

Andrew
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jakeisawake at gmail

Apr 11, 2012, 7:00 PM

Post #4 of 26 (2202 views)
Permalink
Re: simultaneous viewing [In reply to]

On 4/11/12, Jerome Yuzyk <jerome [at] supernet> wrote:
>
> Does anyone use VNC to have more than one machine display content from
> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
> between. I don't care about sound from the kitchen - I can turn up volume
> on the main machine, but video would be good as long as it doesn't lag
> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
> night, and a guy's gotta eat!

this may seem obvious, but you haven't stated a resason why you can't
just use mythfrontend. so, why not just use mythfrontend?
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raymond at wagnerrp

Apr 11, 2012, 7:02 PM

Post #5 of 26 (2195 views)
Permalink
Re: simultaneous viewing [In reply to]

On 4/11/2012 21:56, Andrew Leech wrote:
> On 12/04/12 11:45, Raymond Wagner wrote:
>> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>>> Does anyone use VNC to have more than one machine display content from
>>> MythTV? I have a machine in my kitchen (for recipes) with wired
>>> gigabit
>>> between. I don't care about sound from the kitchen - I can turn up
>>> volume
>>> on the main machine, but video would be good as long as it doesn't lag
>>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>>> night, and a guy's gotta eat!
>>
>> Are you asking if you can use VLC to stream video? If so, no.
>>
> No, he's asking about VNC, not vlc.
> I've used VNC to remote admin my main box at times, basically as a
> wireless keyboard.

Erm, yeah... VNC. VNC cannot be used to stream video.
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nick.rout at gmail

Apr 11, 2012, 9:28 PM

Post #6 of 26 (2190 views)
Permalink
Re: simultaneous viewing [In reply to]

On Thu, Apr 12, 2012 at 2:00 PM, Per Hatlevik <jakeisawake [at] gmail> wrote:
> On 4/11/12, Jerome Yuzyk <jerome [at] supernet> wrote:
>>
>> Does anyone use VNC to have more than one machine display content from
>> MythTV?  I have a machine in my kitchen (for recipes) with wired gigabit
>> between. I don't care about sound from the kitchen - I can turn up volume
>> on the main machine, but video would be good as long as it doesn't lag
>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>> night, and a guy's gotta eat!
>
> this may seem obvious, but you haven't stated a resason why you can't
> just use mythfrontend. so, why not just use mythfrontend?

I think he wants it synchronised with what the main system on the
other side of the room is doing.
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pieter at insync

Apr 11, 2012, 9:53 PM

Post #7 of 26 (2192 views)
Permalink
Re: simultaneous viewing [In reply to]

Hi,



Look for ffserver live screen cast. The demo generally shows a screen grab onto a rtp server. The player can then be vlc on the client. Should get you very close to live, about 200ms lag



Cheers,



Pieter
From : Nick Rout
To : Discussion about MythTV;
Subject : Re: [mythtv-users] simultaneous viewing


On Thu, Apr 12, 2012 at 2:00 PM, Per Hatlevik wrote: > On 4/11/12, Jerome Yuzyk wrote: >> >> Does anyone use VNC to have more than one machine display content from >> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit >> between. I don't care about sound from the kitchen - I can turn up volume >> on the main machine, but video would be good as long as it doesn't lag >> badly. It's the start of hockey playoffs, and I record 3 or 4 games a >> night, and a guy's gotta eat! > > this may seem obvious, but you haven't stated a resason why you can't > just use mythfrontend. so, why not just use mythfrontend? I think he wants it synchronised with what the main system on the other side of the room is doing. _______________________________________________ mythtv-users mailing list mythtv-users [at] mythtv http://www.mythtv.org/mailman/listinfo/mythtv-users


mythtv at thegowers

Apr 12, 2012, 12:43 AM

Post #8 of 26 (2180 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12 Apr 2012, at 03:02, Raymond Wagner wrote:

> On 4/11/2012 21:56, Andrew Leech wrote:
>> On 12/04/12 11:45, Raymond Wagner wrote:
>>> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>>>> Does anyone use VNC to have more than one machine display content from
>>>> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
>>>> between. I don't care about sound from the kitchen - I can turn up volume
>>>> on the main machine, but video would be good as long as it doesn't lag
>>>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>>>> night, and a guy's gotta eat!
>>>
>>> Are you asking if you can use VLC to stream video? If so, no.
>>>
>> No, he's asking about VNC, not vlc.
>> I've used VNC to remote admin my main box at times, basically as a wireless keyboard.
>
> Erm, yeah... VNC. VNC cannot be used to stream video.
> _______________________________________________

My approach was to run a long hdmi cable to the kitchen and clone the the display to both outputs on the graphics card, for sound I have a custom .asoundrc file to send the same 2 channel pcm stream to my AV amp via spdif and to the kitchen TV via HDMI additionally it uses the ladspa delay_5s plugin to add a delay to the HDMI feed to synchronise the sound from the two outputs.

This limits me to watching the same program in the kitchen as in the lounge, sometimes I wish I could watch something different.

Ideally I would like two new features to mythfrontend, 1. add functionality to broadcast a playback timestamp for the currently playing file. 2. add functionality to allow "slave" frontends to optionally synchronise to this timestamp (with a configurable varience to allow for syncing audio). The first should be fairly easy, I'm not sure about the second. I would be willing to have a stab at implementing this if it where likely to be accepted by the devs.

Cheers
Russell

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tortise at paradise

Apr 12, 2012, 4:30 AM

Post #9 of 26 (2170 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12/04/2012 1:45 p.m., Raymond Wagner wrote:
> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>> Does anyone use VNC to have more than one machine display content from
>> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
>> between. I don't care about sound from the kitchen - I can turn up volume
>> on the main machine, but video would be good as long as it doesn't lag
>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>> night, and a guy's gotta eat!
>
> Are you asking if you can use VLC to stream video? If so, no.

My understanding is that you can use VLC to unicast, dual cast, and
multicast a recording. It takes some setting up but can be done, I've
done it, manually its fiddly as hell and multicast somewhat takes over
the LAN, presuming compatible hardware and no WiFi issues etc...

The best approach I am aware of to do this (after much help from a
number of people to understand the issues) is to write an app which
reads the master frontends position/recording and tell the second one to
mimic the master frontend and pull it in a coordinated fashion from the
backend. I am thinking a webpage might be written to do this.

0.25 may have some increased possibility with the http thing, I've not
got to that yet.
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tortise at paradise

Apr 12, 2012, 4:37 AM

Post #10 of 26 (2176 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12/04/2012 7:43 p.m., Russell Gower wrote:
>
> On 12 Apr 2012, at 03:02, Raymond Wagner wrote:
>
>> On 4/11/2012 21:56, Andrew Leech wrote:
>>> On 12/04/12 11:45, Raymond Wagner wrote:
>>>> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>>>>> Does anyone use VNC to have more than one machine display content from
>>>>> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
>>>>> between. I don't care about sound from the kitchen - I can turn up volume
>>>>> on the main machine, but video would be good as long as it doesn't lag
>>>>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>>>>> night, and a guy's gotta eat!
>>>>
>>>> Are you asking if you can use VLC to stream video? If so, no.
>>>>
>>> No, he's asking about VNC, not vlc.
>>> I've used VNC to remote admin my main box at times, basically as a wireless keyboard.
>>
>> Erm, yeah... VNC. VNC cannot be used to stream video.
>> _______________________________________________
>
> My approach was to run a long hdmi cable to the kitchen and clone the the display to both outputs on the graphics card, for sound I have a custom .asoundrc file to send the same 2 channel pcm stream to my AV amp via spdif and to the kitchen TV via HDMI additionally it uses the ladspa delay_5s plugin to add a delay to the HDMI feed to synchronise the sound from the two outputs.
>
> This limits me to watching the same program in the kitchen as in the lounge, sometimes I wish I could watch something different.
>
> Ideally I would like two new features to mythfrontend, 1. add functionality to broadcast a playback timestamp for the currently playing file. 2. add functionality to allow "slave" frontends to optionally synchronise to this timestamp (with a configurable varience to allow for syncing audio). The first should be fairly easy, I'm not sure about the second. I would be willing to have a stab at implementing this if it where likely to be accepted by the devs.

Damn, should have read the whole thread first, apologies. I think any
reasonable dev is unlikely to accept that proposition. The app needs to
be written and tested, I think it would work, however I think one can
only expect the dev's to consider something concrete. Similarly using
the frontend network interface its possible (I think) to write something
that can be independent of the code, so long as it complies with the
protocols it could remain independent of the code. I think that
something tested and working for a number of people is likely to get a
favourable hearing from the dev's, but I can't expect them to commit to
anything before they see it.

An obvious issue to me is how many frontends will be coordinated slaves
and how will they be controlled in the various combinations?
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brian at interlinx

Apr 12, 2012, 5:04 AM

Post #11 of 26 (2167 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12-04-12 07:30 AM, tortise wrote:
>
> multicast somewhat takes over
> the LAN,

This statement doesn't make any sense. You clearly don't understand how
multicast works. Multicast generates no more traffic than a single
unicast stream (i.e. one listener). That is in fact the *entire* point
of multicast. The stream is sent out onto the "LAN" (to use your term)
once and any "listeners" that want to use it just use it, with each
"listener" using the exact same single stream.

Multicast is the IP network equivalent of "radio broadcast" where I use
the term radio here as the generic use of radio that includes of course
the television band. A stream is just "spewed" out there (one copy only
of course just like each television watcher doesn't get their own copy
of an OTA broadcast) and anyone who wants to "tune in" just does.

> The best approach I am aware of to do this (after much help from a
> number of people to understand the issues) is to write an app which
> reads the master frontends position/recording and tell the second one to
> mimic the master frontend and pull it in a coordinated fashion from the
> backend.

This is the approach that would "take over the LAN" as you end up with
each frontend creating duplicate network streams.

I guess what would be neat is for the myth streaming protocol to just
use multicast for all streams (even for single FEs since it's no more
taxing on the network than a unicast stream anyway), all of the time and
then have an option in the FE to "join" existing playing FEs.

b.
Attachments: signature.asc (0.26 KB)


mythtv at thegowers

Apr 12, 2012, 5:08 AM

Post #12 of 26 (2168 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12 Apr 2012, at 12:37, tortise wrote:
>> Ideally I would like two new features to mythfrontend, 1. add functionality to broadcast a playback timestamp for the currently playing file. 2. add functionality to allow "slave" frontends to optionally synchronise to this timestamp (with a configurable varience to allow for syncing audio). The first should be fairly easy, I'm not sure about the second. I would be willing to have a stab at implementing this if it where likely to be accepted by the devs.
>
> Damn, should have read the whole thread first, apologies. I think any reasonable dev is unlikely to accept that proposition. The app needs to be written and tested, I think it would work, however I think one can only expect the dev's to consider something concrete. Similarly using the frontend network interface its possible (I think) to write something that can be independent of the code, so long as it complies with the protocols it could remain independent of the code. I think that something tested and working for a number of people is likely to get a favourable hearing from the dev's, but I can't expect them to commit to anything before they see it.
>
> An obvious issue to me is how many frontends will be coordinated slaves and how will they be controlled in the various combinations?
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://www.mythtv.org/mailman/listinfo/mythtv-users
Agreed, I wouldn't expect anything to be accepted until well proven, what I would be looking for is agreement that a well implemented solution would be considered rather than turned down point blank.

I'm not sure how an external application could provided the required timing for near frame accurate synchronisation.

I've not done any real design work yet, but my initial thoughts are that a frontend operating normally would use ip multicasting to announce it's name the file name of the currently playing recording and its current position within the file, this would take place every couple of seconds.

All frontends would listen for the multicast's and provide a play back option for each of them, once playing they would use the time stamp portion of the multicast to remain synchronised.

Regards
Russell
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mythtv at rtr

Apr 12, 2012, 5:09 AM

Post #13 of 26 (2178 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12-04-12 08:04 AM, Brian J. Murrell wrote:
> On 12-04-12 07:30 AM, tortise wrote:
>>
>> multicast somewhat takes over
>> the LAN,
>
> This statement doesn't make any sense.

Sure it does. A typical home network these days uses ethernet switches,
rather than hubs. The switches are smart, they memorize MAC addresses
and then send traffic only where it needs to go, keeping other ports
free for their own traffic.

Multicast defeats that, sending all (multicast) traffic to all ports
all of the time. Much, much heavier network load.

Probably still not a big issue, but the original poster makes a good point.

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max at mjhodgson

Apr 12, 2012, 6:20 AM

Post #14 of 26 (2166 views)
Permalink
Re: simultaneous viewing [In reply to]

The OP would probably (if he is feeling rich) do it with something like these:

http://hiddenwires.co.uk/resourcesnews2010/news20101104-06.html

HDMI Multicasting boxes.

max




On 12 April 2012 13:09, Mark Lord <mythtv [at] rtr> wrote:
> On 12-04-12 08:04 AM, Brian J. Murrell wrote:
>> On 12-04-12 07:30 AM, tortise wrote:
>>>
>>> multicast somewhat takes over
>>> the LAN,
>>
>> This statement doesn't make any sense.
>
> Sure it does.  A typical home network these days uses ethernet switches,
> rather than hubs.  The switches are smart, they memorize MAC addresses
> and then send traffic only where it needs to go, keeping other ports
> free for their own traffic.
>
> Multicast defeats that, sending all (multicast) traffic to all ports
> all of the time.  Much, much heavier network load.
>
> Probably still not a big issue, but the original poster makes a good point.
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://www.mythtv.org/mailman/listinfo/mythtv-users
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matt at mossholder

Apr 12, 2012, 6:34 AM

Post #15 of 26 (2175 views)
Permalink
Re: simultaneous viewing [In reply to]

On Thu, Apr 12, 2012 at 8:09 AM, Mark Lord <mythtv [at] rtr> wrote:

> On 12-04-12 08:04 AM, Brian J. Murrell wrote:
> > On 12-04-12 07:30 AM, tortise wrote:
> >>
> >> multicast somewhat takes over
> >> the LAN,
> >
> > This statement doesn't make any sense.
>
> Sure it does. A typical home network these days uses ethernet switches,
> rather than hubs. The switches are smart, they memorize MAC addresses
> and then send traffic only where it needs to go, keeping other ports
> free for their own traffic.
>
> Multicast defeats that, sending all (multicast) traffic to all ports
> all of the time. Much, much heavier network load.
>
> Probably still not a big issue, but the original poster makes a good point.


That isn't entirely true. Multicast aware switches will only send multicast
packets to the hosts that need them. So it comes down to the capabilities
of your switch.

--Matt


raymond at wagnerrp

Apr 12, 2012, 6:58 AM

Post #16 of 26 (2164 views)
Permalink
Re: simultaneous viewing [In reply to]

On 4/12/2012 07:30, tortise wrote:
> On 12/04/2012 1:45 p.m., Raymond Wagner wrote:
>> On 4/11/2012 21:35, Jerome Yuzyk wrote:
>>> Does anyone use VNC to have more than one machine display content from
>>> MythTV? I have a machine in my kitchen (for recipes) with wired gigabit
>>> between. I don't care about sound from the kitchen - I can turn up
>>> volume
>>> on the main machine, but video would be good as long as it doesn't lag
>>> badly. It's the start of hockey playoffs, and I record 3 or 4 games a
>>> night, and a guy's gotta eat!
>>
>> Are you asking if you can use VLC to stream video? If so, no.
>
> My understanding is that you can use VLC to unicast, dual cast, and
> multicast a recording. It takes some setting up but can be done, I've
> done it, manually its fiddly as hell and multicast somewhat takes over
> the LAN, presuming compatible hardware and no WiFi issues etc...

Misspelling. The original post said VNC, and I meant VNC, not VLC.
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mtdean at thirdcontact

Apr 12, 2012, 9:22 AM

Post #17 of 26 (2167 views)
Permalink
Re: simultaneous viewing [In reply to]

On 04/12/2012 08:08 AM, Russell Gower wrote:
> On 12 Apr 2012, at 12:37, tortise wrote:
>>> Ideally I would like two new features to mythfrontend, 1. add functionality to broadcast a playback timestamp for the currently playing file. 2. add functionality to allow "slave" frontends to optionally synchronise to this timestamp (with a configurable varience to allow for syncing audio). The first should be fairly easy, I'm not sure about the second. I would be willing to have a stab at implementing this if it where likely to be accepted by the devs.
>> Damn, should have read the whole thread first, apologies. I think any reasonable dev is unlikely to accept that proposition. The app needs to be written and tested, I think it would work, however I think one can only expect the dev's to consider something concrete. Similarly using the frontend network interface its possible (I think) to write something that can be independent of the code, so long as it complies with the protocols it could remain independent of the code. I think that something tested and working for a number of people is likely to get a favourable hearing from the dev's, but I can't expect them to commit to anything before they see it.
>>
>> An obvious issue to me is how many frontends will be coordinated slaves and how will they be controlled in the various combinations?
> Agreed, I wouldn't expect anything to be accepted until well proven, what I would be looking for is agreement that a well implemented solution would be considered rather than turned down point blank.
>
> I'm not sure how an external application could provided the required timing for near frame accurate synchronisation.
>
> I've not done any real design work yet, but my initial thoughts are that a frontend operating normally would use ip multicasting to announce it's name the file name of the currently playing recording and its current position within the file, this would take place every couple of seconds.
>
> All frontends would listen for the multicast's and provide a play back option for each of them, once playing they would use the time stamp portion of the multicast to remain synchronised.
>

During playback, timing will drift from "absolute" independently on
different systems depending on what's happening. Therefore, you would
need an very-well-designed approach for synchronizing playback on
multiple devices, including a protocol for control and a protocol for
playback sync.

There are protocols specifically designed for this, such as those used
by Sonos, Slimserver UDP protocol, and Logitech's Squeezebox (though
Squeezebox may just try to start playback at the same time and ignore
synchronization) or even RTSP (which was used by the "Cidero controller"
for this purpose*), and if we were to accept something to allow this, we
would want to use some "standard" protocol, that's also likely to
interoperate with other devices. (However, it would obviously also need
to be an open protocol that we're allowed to use.)

Most likely the best approach would be to implement the design so that
it works for audio-only playback to start, then extend it to cover
video, too (which would likely follow nicely, since video playback
timing is based on audio timing).

In 2009, Daniel K discussed the idea a bit on IRC with a couple other
devs/users, and he might be able to give you more information about what
we would and wouldn't want. Feel free to send a quick message to the
-dev list proposing the idea (and the more research you can do before
then--such as regarding possible protocols and their
capabilities/limitations--the better). I'd suggest you try to keep the
initial post short to make it more likely that the right people will
read it/reply (so it doesn't seem like so much work to send a reply).

Mike

*Though I can't find it on any existing web site, today, this seems to
be the document that was ref'ed:

http://repo.or.cz/w/learning-java-upnp.git/blob/HEAD:/cidero/doc/html/multiRendererSync.html

which documents the approach used by:

http://repo.or.cz/w/learning-java-upnp.git/blob/HEAD:/cidero/doc/html/mediaController.html

Though the approach documented there sounds like one that would not work
well on MythTV--where even within one user's network, various frontends
are sufficiently different that timing/sync would drift significantly.
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jerome at supernet

Apr 12, 2012, 2:54 PM

Post #18 of 26 (2140 views)
Permalink
Re: simultaneous viewing [In reply to]

On Wednesday, April 11, 2012 08:00:29 PM Per Hatlevik
<jakeisawake [at] gmail> wrote:
> On 4/11/12, Jerome Yuzyk <jerome [at] supernet> wrote:
> > Does anyone use VNC to have more than one machine display content from
> > MythTV? I have a machine in my kitchen (for recipes) with wired
> > gigabit between. I don't care about sound from the kitchen - I can
> > turn up volume on the main machine, but video would be good as long
> > as it doesn't lag badly. It's the start of hockey playoffs, and I
> > record 3 or 4 games a night, and a guy's gotta eat!
>
> this may seem obvious, but you haven't stated a resason why you can't
> just use mythfrontend. so, why not just use mythfrontend?

Because I have a crufty old 0.21 FE/BE and really only want video since I
can turn up the main system for sound.

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jam at tigger

Apr 12, 2012, 5:01 PM

Post #19 of 26 (2139 views)
Permalink
Re: simultaneous viewing [In reply to]

On 13/04/2012, at 4:09 AM, mythtv-users-request [at] mythtv wrote:

>>>> Ideally I would like two new features to mythfrontend, 1. add functionality to broadcast a playback timestamp for the currently playing file. 2. add functionality to allow "slave" frontends to optionally synchronise to this timestamp (with a configurable varience to allow for syncing audio). The first should be fairly easy, I'm not sure about the second. I would be willing to have a stab at implementing this if it where likely to be accepted by the devs.
>>> Damn, should have read the whole thread first, apologies. I think any reasonable dev is unlikely to accept that proposition. The app needs to be written and tested, I think it would work, however I think one can only expect the dev's to consider something concrete. Similarly using the frontend network interface its possible (I think) to write something that can be independent of the code, so long as it complies with the protocols it could remain independent of the code. I think that something tested and working for a number of people is likely to get a favourable hearing from the dev's, but I can't expect them to commit to anything before they see it.
>>>
>>> An obvious issue to me is how many frontends will be coordinated slaves and how will they be controlled in the various combinations?
>> Agreed, I wouldn't expect anything to be accepted until well proven, what I would be looking for is agreement that a well implemented solution would be considered rather than turned down point blank.
>>
>> I'm not sure how an external application could provided the required timing for near frame accurate synchronisation.
>>
>> I've not done any real design work yet, but my initial thoughts are that a frontend operating normally would use ip multicasting to announce it's name the file name of the currently playing recording and its current position within the file, this would take place every couple of seconds.
>>
>> All frontends would listen for the multicast's and provide a play back option for each of them, once playing they would use the time stamp portion of the multicast to remain synchronised.
>>
>
> During playback, timing will drift from "absolute" independently on
> different systems depending on what's happening. Therefore, you would
> need an very-well-designed approach for synchronizing playback on
> multiple devices, including a protocol for control and a protocol for
> playback sync.

[snip]

... and I pause my playback ... and havoc engulfs the multicast users (or worse pause has no effect)

James
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jyavenard at gmail

Apr 12, 2012, 6:14 PM

Post #20 of 26 (2135 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12 April 2012 22:09, Mark Lord <mythtv [at] rtr> wrote:
> Sure it does.  A typical home network these days uses ethernet switches,
> rather than hubs.  The switches are smart, they memorize MAC addresses
> and then send traffic only where it needs to go, keeping other ports
> free for their own traffic.

That's not at all how a home (dumb) switch work for multicast traffic.
Only a L2/L3 managed switch with IGMP snooping would act like what you
describe.

Multicast is muticast, it is sent to all members of the network.

>
> Multicast defeats that, sending all (multicast) traffic to all ports
> all of the time.  Much, much heavier network load.

It isn't heavier load, it's designed to carry that load to start with.

The issue however with multicast is when you have a bridged wireless
network. Multicast rate by default on a 802.11g network is at 1Mbit/s
only. Sending multicast will saturate the wireless network which would
end up saturating the whole network.

That's when you need a switch supporting IGMP snooping, so the data is
only sent to the devices requesting it.
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tortise at paradise

Apr 12, 2012, 11:35 PM

Post #21 of 26 (2132 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12/04/2012 11:37 p.m., tortise wrote:

> An obvious issue to me is how many frontends will be coordinated slaves
> and how will they be controlled in the various combinations?

(Seeing if I can reconnect the runaway thread)

On 13/04/2012 12:01 p.m., James Linder wrote:
> ... and I pause my playback ... and havoc engulfs the multicast users
(or worse pause has no effect)
>
> James

If I was doing this one thing I'd design into this would be a web page
which pauses ALL linked frontends (expect android to display this page)
however single remotes would ordinarily still be able to
interfere....user discipline or more complex design are likely options....

Reference: http://www.mythtv.org/wiki/Frontend_control_socket

No option to suspend IR control of a linked FE (that I can see) was
foreseen however lots has been.

Other web page features would be WOL for frontends, frontend status,
frontend individual and group inclusion / exclusion....

An alternative more elegant UI feature might be a frontend webpage
"switch" that makes a group of frontends behave all the same, i.e. pause
one and they all pause, so they all do the same, obviously there are
issues to this approach however one has to start with a goal in mind,
this seems a good one to me. The above socket does not seem to be
capable of this level of functioning to my glance over what we have there.
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nick.rout at gmail

Apr 13, 2012, 12:03 AM

Post #22 of 26 (2131 views)
Permalink
Re: simultaneous viewing [In reply to]

On Fri, Apr 13, 2012 at 6:35 PM, tortise <tortise [at] paradise> wrote:
> On 12/04/2012 11:37 p.m., tortise wrote:
>
>> An obvious issue to me is how many frontends will be coordinated slaves
>> and how will they be controlled in the various combinations?
>
>
> (Seeing if I can reconnect the runaway thread)
>
>
> On 13/04/2012 12:01 p.m., James Linder wrote:
>> ... and I pause my playback ... and havoc engulfs the multicast users (or
>> worse pause has no effect)
>>
>> James
>
> If I was doing this one thing I'd design into this would be a web page which
> pauses ALL linked frontends (expect android to display this page) however
> single remotes would ordinarily still be able to interfere....user
> discipline or more complex design are likely options....
>
> Reference:  http://www.mythtv.org/wiki/Frontend_control_socket
>
> No option to suspend IR control of a linked FE (that I can see) was foreseen
> however lots has been.
>
> Other web page features would be WOL for frontends, frontend status,
> frontend individual and group inclusion / exclusion....
>
> An alternative more elegant UI feature might be a frontend webpage "switch"
> that makes a group of frontends behave all the same, i.e. pause one and they
> all pause, so they all do the same, obviously there are issues to this
> approach however one has to start with a goal in mind, this seems a good one
> to me.  The above socket does not seem to be capable of this level of
> functioning to my glance over what we have there.

I am struggling to see the use case here. Sure, I once had a house
full of people round to watch a rugby game, more people than were
comfortable in one room so half watched in each lounge room. Other
than that type of situation (which was Live anyway and is easier
outside myth), what really is the benefit?

Sounds like a use case for a meglamaniac who wants their whole house
watching the same thing, with said meglamaniac controlling via one
remote control.

These conversations come up regularly on this list, and I am yet to
see a use case that really makes sense in the mythtv context.

Thinking of situations where I see many screens displaying the same
thing, I think of bars with sport or fuzzy music videos playing, which
need to be exactly synched or it just doesn't work. Far easier to do
with a network of HDMI cables back to an hdmi splitter, all fed from
the same source.
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linux at thehobsons

Apr 13, 2012, 2:16 AM

Post #23 of 26 (2128 views)
Permalink
Re: simultaneous viewing [In reply to]

Nick Rout wrote:
>tortise <tortise [at] paradise> wrote:
> >
> > If I was doing this one thing I'd design into this would be a web
>page which
>> pauses ALL linked frontends (expect android to display this page) however
>> single remotes would ordinarily still be able to interfere....user
> > discipline or more complex design are likely options....

I'd implement it in such a manner that one frontend (the master)
would start watching as normal, then others could "join in". Whatever
the master frontend did, the remotes would follow - just like remote
TVs running off the back of a Sky box (but without the remote
control).
Through whatever process, the master frontend keeps the others
informed of what it's doing and where in the payback it is, so the
others can keep themselves in sync. I can imagine it might take a few
seconds after any pause/skip/whatever for the remotes to resync, but
for the use cases I've seen talked about, this isn't likely to be an
issue.


>I am struggling to see the use case here.
...
>These conversations come up regularly on this list, and I am yet to
>see a use case that really makes sense in the mythtv context.

One that comes up regularly is someone who moves around between rooms
- eg popping into the kitchen to get snacks/drinks etc. They can have
the TV on in the kitchen so they don't miss out while sorting out the
'catering' for their guests.

Taking your example, you've a house full of guests to watch the
rugby, and as a good host you'd be expected to keep them adequately
supplied with food and drink. You **may** be able to just have a
third telly on in the kitchen also showing live TV, but for many
people, they don't get signals they can tune into with their telly
(for example, satellite or cable where they need a provider supplied
receiver for each device). Unless they've shelled out to pipe video
around the house, they may be reliant on Myth to connect to the
receiver and pipe it around via IP.

So the use case for your example is :
The rugby is only available on <pay TV, satellite, cable, whatever>.
You don't have enough receivers, or enough in the right places, or
enough with the right subscriptions to show the game live on all the
TVs you want to.
You don't want to miss out while in the kitchen being a good host.
You *do* have

I've heard this IP stuff is the way of the future, can't see it
catching on myself :D

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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mythtv at rtr

Apr 13, 2012, 5:48 AM

Post #24 of 26 (2122 views)
Permalink
Re: simultaneous viewing [In reply to]

On 12-04-13 03:03 AM, Nick Rout wrote:
..
> I am struggling to see the use case here. Sure, I once had a house
> full of people round to watch a rugby game, more people than were
> comfortable in one room so half watched in each lounge room. Other
> than that type of situation (which was Live anyway and is easier
> outside myth), what really is the benefit?
..

I don't need it here, but I have visited homes of many people
where they have 3-4 TV sets always "on" (wasteful, yes)
and tuned to the same program (Live TV).

So when they move about the house from room to room,
there is full continuity in the sound and video from each set.
For people like that, accustomed to Live TV, having their PVR
sync all of the displays is a no-brainer. For the user, at least.

In MythTV this could be done as a totally frontend thing.
The way I would do it, is like this:

-- each frontend MUST use NTP with the exact same time servers
to synchronize to a common clock.

-- each frontend would listen on a TCP or UDP port for directives
from other frontends.

-- each frontend would periodically (once a second?) broadcast
their current playback timecode to all other frontends.

-- each frontend would look at the received timecodes, average
them all (including their own in the mix), and then adjust
their local playback offset towards the average value.

-- Any PAUSE event (from keyboard, remote-control) received by
any frontend is broadcast to all other frontends, along with
the timecode at the originating frontend.

-- all other frontends would then replicate the PAUSE event
and set their own local playback timecode to match.

In the above points, I use "timecode" to mean "playback offset
within the current file" or whatever the equivalent Mythtv
term for that happens to be. :)

Cheers
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mtdean at thirdcontact

Apr 13, 2012, 9:42 AM

Post #25 of 26 (2111 views)
Permalink
Re: simultaneous viewing [In reply to]

On 04/13/2012 03:03 AM, Nick Rout wrote:
> I am struggling to see the use case here. Sure, I once had a house
> full of people round to watch a rugby game, more people than were
> comfortable in one room so half watched in each lounge room. Other
> than that type of situation (which was Live anyway and is easier
> outside myth)

er, probably easier inside MythTV by watching a recording in progress
(so you have pause/rew/ffwd/... and the ability to start it when the
guests arrive, regardless of when it starts and--if you start late or if
you pause it any--the ability to skip over some commercials or whatever).

http://www.gossamer-threads.com/lists/mythtv/users/387302#387302

The only thing about "Live" playback that's not ideal in MythTV is using
Live TV for it, rather than playing back a recording in progress. "Live
TV" is all about, "I have no clue what I want to watch, so I'll just
randomly switch channels so I think I'm going to stumble on some
treasure." Watching a recording "live" as it records works great--and
from as many frontends as desired.

> Sounds like a use case for a meglamaniac who wants their whole house
> watching the same thing, with said meglamaniac controlling via one
> remote control.
>
> These conversations come up regularly on this list, and I am yet to
> see a use case that really makes sense in the mythtv context.
>
> Thinking of situations where I see many screens displaying the same
> thing, I think of bars with sport or fuzzy music videos playing, which
> need to be exactly synched or it just doesn't work. Far easier to do
> with a network of HDMI cables back to an hdmi splitter, all fed from
> the same source.

Though I do agree that I wouldn't have any use for simultaneous playback
(of either audio or video) for exactly that reason--there are
significantly easier ways to achieve the same via routing cables to the
right places. And, especially with video, the video-processing
circuitry in different displays has significantly different
characteristics that result in widely-differing delays--sufficient,
even, to cause echoes, etc., when trying to synchronize playback.

Mike
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