Does anyone know of a way to ensure two or more apple TVs can remain synchronized when receiving/viewing the same free to air program via channels and HD Home run?
The scenario I am try to fix is we use a common HD Home run connect to feed our apple TVs with channels installed and wish to watch the same free to air program in multiple rooms without any substantial echo.
Ain't gonna happen.
You get the echo effect because even if the sound arrives at and is emitted by each device at exactly the same time, it takes time to travel through the air from that point to where you are. If you're closer to one device than another: Echo effect. The greater the distance difference, the greater the effect.
Then there are ceilings, walls, possibly bare floors, cabinetry, any hard-surfaced furniture, etc.
You’d be surprised. Because there’s practically any processing or buffering, you can start a program on two TVs and they’re pretty close to in sync.
Don’t pause either of them, and if you do, stop playback and restart.
I’ve done this in my family room and adjacent kitchen with pretty great results. At least on the Apple TV.
Obviously ymmv.
I don't doubt that for a minute. But...
Sure. If I fire Channels up on, say, the living room TV and computer room TV, and stand more-or-less equidistant from each: No echo. But if the TV's on in the family room, which would put it about twice as far away as the other two: Echo.
My wife's hearing is much better than mine. I've actually had it happen where we were watching the same thing, her in the family room and me in the computer room, and have her ask me to turn it down a bit, because the echo effect was driving her nuts.
I am wondering if this is more of an HD Homerun feature. – I don’t know how synchronized the two streams of a same program are when leaving it. Quite often there can be a couple of seconds between two programs and sometimes they are very close etc.
I have used exactly the same set up with a bunch of cable tv set top boxes and performance has been good enough for family use etc. so am fairly confident the physical environment is not a significant contributing factor for this scenario. With that said the wife has suggested installing doors to solve the issue!
It’s true you’ll get an echo. You can’t beat acoustics. But if you’re just worried about being at the same time, it works well.
I imagine it might be more hit-and-miss with the synch if you are streaming directly from the tuners to client, as each client will have its own separate stream from the tuner(s) to the respective client. However, they might be a bit more in synch if you have a Channels DVR server and "Tuner Sharing" enabled; in this way, there is only a single source of the stream, regardless of the number of clients, all being served from the DVR server rather than individually from tuner(s) directly.
I also imagine that your network topology and bandwidth might play a part, too, as several 15Mbps streams flying over a WiFi network might saturate it, whereas the same bandwidth may not be an issue at all with GbE.
I have airplay playing on multiple speakers throughout my house and don't notice this at all.
It takes sound 0.029 seconds to travel 10 metres.
https://helpx.adobe.com/au/audition/using/delay-echo-effects.html says...
The Delay And Echo > Delay effect can be used to create single echoes, as well as a number of other effects. Delays of 35 milliseconds or more create discrete echoes, while those between 15‑34 milliseconds can create a simple chorus or flanging effect. (These results won’t be as effective as the Chorus or Flanger effects in Adobe Audition, because the delay settings don’t change over time.)
So at that distance you won't get an echo effect, and if the distance is less than 5 metres you won't get any effect at all.
Sorry to revive this thread - very close to what I was looking to do.. From what I understand the 'Shared Tuner' only works when watching live TV. Is it possible to synchronize playback of Channels DVR recordings? I am having a World Cup party and was trying to keep the TV output in sync as much as possible
BTW - Sonos is an expensive solution but pretty awesome at playing audio from a single source in multiple rooms simultaneously. If I could do something similar with my video recordings that would be awesome.
It's never going to be possible for an app like Channels to solve this problem well enough to be a well-supported feature. The insurmountable constraint is that different television models add different amounts of delay for postprocessing. Only CRT televisions can display their input signal without any processing delay.
Suppose you have TV 1 and TV 2, each with an Apple TV attached running Channels. Even if both Channels apps were sending identical, perfectly synced video out over HDMI, things would still be out of sync if TV 1 adds 100ms of delay while TV 2 adds 300ms of delay.
@dbloom- yeah what you mention makes sense regarding latencies of various TVs.. Though I don't think my potential use-case is quite as rigid. If you had the screens side by side I agree it would be painful to watch... But if viewing in different rooms some differences would be tolerable.
My reference point for this request is the 'TV Tuner Sharing' feature in Channels for Live TV. From what I've read about this feature, 2 ATVs watching the same channel will share a single tuner on the HDHomeRun. Effectively, Channels DVR records the video and serves it back to the 2 ATVs. Whenever I use this feature it is great - both of my TVs have video that is 'almost' perfectly synchronized (my ATVs connect via 1GB ethernet). I'll turn off the audio from 1 of the TVs (I have Sonos in my house which makes this easier). For watching sports it is pretty effective.. So basically if Channels could support a similar type of synchronization from an existing recording it would satisfy my use-case (I think).
I imagine you could craft a script that would take a file number as a parameter, and the IP addresses of the Channels clients you would like to have play the recording, and send play commands to each client.
Something like:
#!/bin/sh
FILE=$1
shift
for _client in $@
do
curl -XPOST http://${_client}:57000/api/play/recording/${FILE}
done
Pass the file number you wish to play as the first parameter, and then follow that with the IP address of each client that you wish to have play the file back.
(Of course, there may be errors as I just typed that out real quick without any testing ... but a little trial and error ought to give you results rather quickly.)
Is the problem that you want to be able to pause and rewind and have the other tv be in sync?
Otherwise, just playing a live stream on each and never seeking will have them in pretty much perfect sync for live broadcasts.
Yeah, if it’s a recording, doing it like this would be your best bet. Then never seek 
I'll give it a shot - thanks for the tips..
BTW - how do I get the 'recording_id' value for passing to the API - '/api/play/recording/{recording_id}' ??
If you select "View Details" from a movie/episode's listing in the Recordings section of the Recording tab in the DVR WebUI, there is a "File ID" which is what you want.
(It's not that easy to find, but that's mostly because it's used mostly for internal purposes.)
Couldn't find FileID on the 'View Details' screen.. Though found the DVR API calls.. This one worked for me:
A little out of scope and an expensive fix for this problem...Sonos. No clue how they do it, but no echo in multi room audio with Sonos.
Pick one of the TVs as the Sonos audio source, then play that source on both TVs while starting the video streams on both TVs simultaneously. This would give the desired effect that was being asked for.
I’ve done this for UFC fights and the super bowl when having a party. Same program on multiple TVs in different rooms, but audio from only the main TV to all the other Sonos speakers in house.
i do this too. It’s mostly perfect for sports because there’s no lips on screen 
Sports is the only real scenario I have for multi room anyways. But filling your whole house with the event is one of the joys of Sonos.