Tested the issue on chrome reported version 64.0.3282.186 using Mac 10.12.6 with steps mentioned below:
1) Launched chrome reported version and opened URL: https://appr.tc/r/mystereotestroom?stereo=true&audio=echoCancellation=false in two tabs
2) Clicked on Allow and then "JOIN"
3) Heard some sort of sound when joined the room

@Reporter: Please find the attached screen cast for your reference and let us know if we missed anything in reproducing the issue, please provide your feedback on it which helps us in further triaging it. If possible could you please provide screen cast of excepted behaviour which helps us in better understanding it.

Thanks!

Deleted: 818180.mp4 5.8 MB

	818180.mp4 5.8 MB View Download

The issue needs a stereo input, and a way of measuring the output. I'm using a virtual audio device and audio plugin to view the channels: it shows that stereo audio is being put, and dual mono is being output.

I am using Chrome Beta Version 65.0.3325.106 on one tab, and Chrome Canary Version 67.0.3364.0 in the other tab. Both Chrome versions have the stereo bug, it is a regression from Chrome 64. 

Screencast attached

Deleted: chrome66 bug.mp4 3.3 MB

	chrome66 bug.mp4 3.3 MB View Download

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

As per comment#3 from the reporter, as he mentioned "issue needs a stereo input" device to test the issue, as ET team don't have stereo input setup to test and confirm the same. Hence adding TE-Hardware-Dependency label and adding Blink>WebRTC>Audio component. Could someone from the Blink>WebRTC>Audio team have a look at this issue and help in triaging this better.

Thanks!

>the reporter, as he mentioned "issue needs a stereo input"

Reporter is a "she" (relevant to mention, it's International Women's Day). Thanks for investigating, happy to commit to further testing on my part.

The echo canceller is mixing to mono, but it should be disabled in this case. Maybe that goes wrong?

studio.pqv9@: could you please make debug recordings? New tab, chrome://webrtc-internals, expand "Create dump", select "Enable diagnostic audio recordings", then either attach files created here or share on Google Drive.

A side note: I've made a fix on Mac pretty recently, but that was for mono devices. That fix is not in the versions tested here; it's in  65.0.3325.109 (on stable channel). Also this problem is a regression. So it doesn't seem related. https://chromiumdash.appspot.com/commit/3ccfcbbac6f7055e92d9da39be10c656617468fb

studio.pqv9: do you have the chance to please make recordings as described in comment #8?

Encountered the same issue here, streamed out stereo Opus from Chrome (disabled audio signal processing), Firefox as receiver has the stereo effect output, but Chrome does not.
Tested versions: Chrome v57, v62, v63, v67
Result: 
      Has stereo output : v57;  
      No stereo: v62, 63, 67;

Attached the dump wav file

Deleted: audio_debug.output.5.wav 3.9 MB

audio_debug.output.5.wav 3.9 MB Download

Thanks for the report. Does this only happen on Mac? I'll see if I can repro too.

studio.pqv9: did you mean that the regression is from M64 to M65, that is M64 works and M65 doesn't? Or that the issues started with M64 (the original report says M64)?

According to comment #10, the problem is present in M62 and M63 too.

Does it happen on other platforms than Mac?

Does it happen with other codecs?

viswa.karala: can you help bisecting this?

Some speculations on causes; could be related to Opus, or a change in mixing on the receive side done some time ago in WebRTC.

I have reproduced the problem. Sending from a Windows machine using Chrome stable, receiving on a Mac using ToT developer build. When using Firefox on the receive side, stereo works.

Tested with iSAC, same issue.
https://appr.tc/?stereo=true&audio=echoCancellation=false&asc=ISAC/16000

viswa.karala: can you help bisecting this?

As per comment# 6 TE-team don't have stereo input device to test and confirm the issue

grunell@: Could you please confirm if the Test URL in C#16 would require stereo input device or alternatively is there any sample test page to test the same without any stereo device. Appreciate your help in further clarification to try a repro and bisect this.

Thanks!

Is this issue related.

https://bugs.chromium.org/p/webrtc/issues/detail?id=8133

We had freeswitch able to send stereo audio to browsers, and this broke in Aug 2017. Chrome 62 see  issue 8133 .  

Does anyone have solution to have chrome browser "play" stereo from opus/48000/2 source?

Currently Firefox works fine in Window,Mac, Android.  

thanks
Stephen

Looks like thats  issue 8133   in webrtc.org, sorry.