Can't get AC3 passthrough to work on Chromecast with Google TV

Plex Players Streaming Devices
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Server Version#: 1.20.3.3483-211702a9f
Player Version#: 8.8.1.21332

I’ve got the new Chromecast with Google TV, and I’m unable to get it to do passthrough of AC3 surround sound to my receiver. It seems that other people have this working, so I’m trying to figure out what I’m doing wrong.

For many years, I’ve been using a Raspberry Pi 3 with Plex Media Player on it, and this works fine with my TV and receiver. Here’s what my setup looks like:


   +-------+    HDMI    +--------------+                                                 
   |  PI   |----------->|              |                                                       
   +-------+            |              |   S/PDIF   +--------------+                    
                        |  SAMSUNG TV  |----------->| JVC RECEIVER |    
   +--------+   HDMI    |              |            +--------------+                 
   | CCWGTV |---------->|              |                                                       
   +--------+           +--------------+

On the Pi, under Plex Settings->Audio, I’ve got “Device Type” = “Optical (S/PDIF)”, and “Passthrough: Dolby Digital (AC3)” checked. When I play a video with AC3, the receiver gets multichannel Dolby sound perfectly.

On the CCWGTV, under the device’s “Advanced Sound Settings”, I’ve got “Format Selection” as “Automatic”. For the Plex app, I’ve got “Passthrough” as “Optical” and “Optical Encodings” as “AC3”. Playing the same video with AC3, I get an error dialog that says

“An error occured when attempting to play this video”

From another post here in this forum, it seems that other people have gotten this work, but I can’t figure out what I’ve got wrong. It seems related to either transcoding or not transcoding audio, but I’m not sure what to tweak.

I’m attaching logs, and it shows a java exception when I try to play my test file (“ac3-dolby-test-5.1-surround”).

Anyone have an idea?

logging.txt (1.2 MB)

Edit to add more info:

I just installed Kodi on the CCWGTV, and then installed the Plex Add-On on Kodi. Set Kodi to do audio passthrough, and that worked! So, I know all my hardware is capable of this, it’s just getting the direct Plex client configured properly, I guess. (Or getting fixed, if it’s a bug)

Edit to correct server version

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There was an update today from Google for the CCWGTV, (200918.015), that seems to have fixed this, mostly

There is a new option under “Settings->Display & Sound”: “Surround Sound” that I switched on.

Under device “Settings->Display & Sound->Advanced Sound Setting->Surround sound format selection”, I chose “Manual” and turned on “Dolby Digital”

On Plex app settings, I’ve got “Passthrough” as “Optical” and “Optical Encodings” as “AC3”.

Now, when I play most videos with 5.1 surround, it’s getting properly transcoded to AC3, and my receiver is handling it. I do seem some issues with playback hanging for some (but not all ) videos with AAC 5.1. Not sure what the issue is there, though.

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I had a similar problem with my Chromecast (2nd gen v 1.49.230269), where my AC3 sound quit working at all. Discovered there’s a new option in Google Home device settings, where my setup didn’t like the “Auto” Surround Sound mode. Set to “AC3 surround sound only” and AC3 tracks are again playing.

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