Hi,
i bought a meCool km2 android tv box amazon link
it works great transcoding ac-4 to ac-3 to get dolby 5.1 sound, when using the hdhomerun app and their atsc3.0 tuners, with the hdhr audio option set to 'passthrough when possible'.
the problem is i want to use the channels app, not hdhomerun app. but with channels i get no sound.
is there a way you can do the same trick as the hdhr app does to pass ac-4 to the mecool box so it can do its transcode thing?
thanks
That's not the box transcoding, it's SiliconDust. For ATSC 3.0 channels they send the AC-4 audio to their servers, transcode it in the cloud, and then send the AC-3 audio back to their app, where it is remuxed with the video stream.
Here is the announcement:
https://mailchi.mp/245e1f09021d/hdhomerun-apps-now-support-atsc-30-audio-on-more-devices
i think youre incorrect.
i agree they use cloud for 'unsupported' ac-4 devices, but mecool supports ac-4
from hdhr forum:
We don't invoke the cloud transcode service unless there is no other option. On the Mecool KM2 Plus decode is done locally unless you disable "Use audio passthrough when possible" to disable using passthrough-transcode.
If the device supports AC-4, then that is native support. Are you saying the box only sort-of supports AC-4, and transcodes it?
Have you enabled the "pass through" option in the HDHR app to ensure that it truly is passing through the untouched AC-4?
yes!
from hdhr forum:
We don't invoke the cloud transcode service unless there is no other option. On the Mecool KM2 Plus decode is done locally unless you disable "Use audio passthrough when possible" to disable using passthrough-transcode.
I think this is where the confusion is:
I think what you mean is:
it works great decoding AC-4 to get 5.1 sound.
From the discussions at SD's forum, the device is flagging its audio decoding capabilities in a manner that individual apps need to check for to allow the audio to pass through.
Does this more closely match what you are asking?
My technical understanding of what the mecool box is doing is not enough to answer that.
my current understanding is that ac-3, ac-4, and eac+ are all just compression formats carrying multi-channel audio tracks ranging from mono up to 7.2 channels.
so my guess is that the mecool is transcoding the newer ac-4 compression format to the older ac-3 compression format and passing that on to my tv for ac-3 audio decoding. just a guess though.
kinda like converting a tar file to zip file without modifying its contents.
yes i think that the mecool is using edid to report it supports ac-4.
and thats what im asking channels to do (if it doesnt already), is to pass the ac-4 along to the mecool box.
could be wrong... but i dont think a dolby license is needed for this.
I installed channels app again (dvr 4.5.1) on the mecool box.
tuned to the atsc3.0 Fox channel, watching usa v iran soccer. not quite sure who is doing what... but i am getting (very low volume) dolby 2.0 on my sonos (connected to my lgtv via optical)
Playbar: Bedroom
Serial Number: 78-28-CA-50-0A-20:1
Sonos OS: S2
Version: 14.19.1 (build 70335220)
Hardware Version: 1.9.1.10-1.2
Series ID: A100
IP Address: 192.168.0.229
Audio In: Dolby Digital 2.0
WM: 1
when i switch to same channel using hdhomerun app, my sonos gets dolby 5.1
Optical doesn’t have the bandwidth for 6 channel audio with pcm which is what channels outputs when surround sound is enabled I think. I think you need to disable surround in the channels app and enable audio pass through on the android tv(if that mi thing has that option). Hdhr app works because they are turning into Dolby digital 5.1 that optical has the bandwidth for.
Actually that probably won’t work either as you sound bar most likely doesn’t support ac4. Does your sound bar support hdmi in?
i dont think thats right. i have "Use audio passthrough when possible" enabled.
from hdhr forum:
We don't invoke the cloud transcode service unless there is no other option. On the Mecool KM2 Plus decode is done locally unless you disable to disable using passthrough-transcode.
So what does the Sonos report when you disable surround sound in the channels app?
ok tried that...
with channels 'surround sound' enabled or disabled, and mecool audio set to auto, i get dolby 2.0
with channels 'surround sound' enabled or disabled, and mecool audio set to passthrough, i get pcm 2.0
which makes me think channels is transcoding ac-4 to pcm and mecool is transcoding pcm to dolby 2.0 when mecool audio is set to auto
i understand the bandwidth limit of optical, but dont 'think' that's at play here.
Ya probably
It kind of is though, you wouldn’t have an issue if you were using hdmi.
I’m assuming you are using the mecool optical out to the Sonos optical in? If your tv has optical out you could try using hdmi for sound from mecool to tv and optical out from tv to Sonos. Your tv might be smart enough to bundle the audio back into dd
nope...
mecool to lgtv and lgtv to sonos via optical. its an older sonos so no hdmi or arc input avail.
mecool has no optical avail either, just hdmi and usb
so im guessing mecool is getting edid info from tv
Its probably negotiating down to what it can handle. I have a Sony Bravia TV that i am using eARC to feed an audio return to my Marantz Receiver. AppleTV HDMI -> Sony TV HDMI -> Marantz. My Sony TV is set to decode Audio and then it sends it to the Marantz. ATSC 3.0 is decoded just fine. It shows on my Marantz as multichannel in when i look at the stats. Its basically decoded AC4 audio.
Might be time for an audio upgrade to support it. I am pretty sure you wouldn't have these problems with a more modern sound bar that has HDMI.
Optical cannot cope with the higher bandwidth needed for newer formats. If you want the truest audio fidelity, you need eARC via HDMI; otherwise any benefit you gain from newer standards is lost.
my bad.... just got this yesterday and was going by amazon specs. so yes spidif connection avail on mecool, but not used. 
Try using that optical on the mecool then. Maybe there is some settings that can be tweaked when using spdif audio output in the mecool settings
