Frequent Drop Outs Using Chromecast Groups

I have several groups setup using Google Devices. One in particular has a Google Homehub, a Google Home, an Onkyo VC-GX30 and a Chromecast Audio.

I was delighted to see Roon supports these as it transforms the attractiveness of the solution for me. (Grouping these devices with Airplay devices would be a huge win for me - as happens with Rogue Amoeba’s Airfoil app - and it would be nice also to use Roon to create the Chromecast groups rather than the Google Home app but that’s a small nice to have)

Unfortunately I’m having frequent issues with the Chromecast group. I have one Roon zone - Kitchen Area - containing the above devices. It’ll play fine then I’ll get periods of poor quality / dropouts before things sort themselves out again and high quality is restored. This happens with radio streams and audio local to my MacBook Pro (2018) which is running Roon.

We run a 3 node Google WiFi setup and have around 30Mbps down and 10Mbps up broadband to the house which is reliable and robust.

Any thoughts on what I can do to sort this out.

Hi @Ian_Robson,

So we can better assist you, may I ask that you please give a little more info about your current setup? Is the MacBook Pro your Core machine? How is it connected to the network?

If you play to any of these zones individually does the same behavior occur or is it only when grouped?

When the dropouts occur is it with any specific types of content? Have you noticed any patterns in what is playing when the dropouts occur?

Hi Dylan, yes, MBP is my core. Library is on an attached USB drive. Network connection is WiFi although it could be Ethernet if you think that would help.

Only occurs so far when grouped. I was playing a high-res album to a chromecast in the furthest corner of the house today and that was fine.

Have tested with internet radio and with local ALAC files. Same issue with both. No obvious pattern.

If it’s possible to use Ethernet with any of the devices involved, it will probably improve your experience. Chromecast grouping can be pretty hard on even the best of WiFi networks; one of the devices in the group receives the audio stream from Roon and then rebroadcasts the audio to the other devices in the group over WiFi. If your MBP is also on WiFi, the amount of wireless bandwidth being used to stream to a 4-device group is roughly four times what it takes to stream to a single Chromecast device; the data is sent from your MBP to one of the devices in the group, and then that device sends it again to the other 3 devices in the group. Also, none of these streams goes directly from device to device; the sender sends it to a WiFi access point and then the AP sends it out to the receiver. This means that sending audio to a 4-device group takes at least 8 times the WiFi bandwidth of the audio stream if all of the devices involved are on WiFi.

I would suggest that you switch your MBP over to Ethernet; if that doesn’t completely fix the problem, the Chromecast Audio supports the Ethernet Adapter for Chromecast. Onkyo states that the VC-GX30 supports “Wired LAN Input via Micro USB”, but I’m not sure exactly what that means in terms of adapters that do and do not work.

Thanks Allan, that’s fascinating and very useful to understand. I’m currently sending a 96/48 stream to two devices and it’s 100% so far in terms is stability.

Given your analysis that makes a lot of sense. I was broadcasting to a 4 device group so a great deal more bandwidth required.

Have Roon considered taking on grouping of chromecast devices in app? That would presumably allow better management of bandwidth?

I would imagine have to use the published API and that’s how it works through that.