Plex Android on x86 Chromebooks 5.1 audio -- only surround channels are played through speakers and headphones

[wpwentzell]

Server Version#: 1.23.3.4707
Player Version#: 8.18.2.25850

Opening a new thread on and old issue as this has apparently not been resolved (or, it was resolved, and then regressed to the original behavior). Here is the original thread that never received official response from the PLEX team: Plex Android on x86 Chromebooks 5.1 audio with no/low/echo-y voice audio channels

FWIW, I do believe this issue is an issue within ChromeOS and not necessarily PLEX, since 5.1 audio plays just fine (all channels are represented) on my Pixel 4A phone.

Summary of the issue:
The PLEX Android app on ChromeOS does not handle 5.1 audio in a way that allows all channels to be heard, both via speakers or headphone output. On my device, when I play back a movie or TV show with 5.1 AC3 audio, which is then direct streamed from my server, I can only hear the surround channels on my device. The center channel, and a believe the front audio channels, are completely lost. Therefore, I cannot hear any vocals. This behavior does not happen on my Fire TV device, nor does it happen on my phone, so this is specifically an Android audio handling issue within ChromeOS (or so I believe).

I have filed a bug report via the Chrome public issue tracker which lists steps on how to reproduce the issue, as well as the details of my device and OS version.

Here is another Chrome bug report on this issue that was marked as resolved, and the fix was supposed to be merged into ChromeOS M89. Interestingly, many users from the original PLEX issue thread noticed the issue did disappear on M89, presumably why the original thread closed. However, can confirm the issue still exists for me, so this issue has NOT been resolved. There is still some discrepancy, likely on ChromeOS’s side, but also potentially on PLEX’s side, that has allowed this issue to re-emerge.

I will be following this issue religiously, as this should be a fixable bug.

[OttoKerner]

The Android emulation in those Chromebooks has a flaw which hasn’t been fixed in ages:
Android apps can query the device for the number of audio channels it has. A regular Android phone usually answers “2” or “1”. So the Plex app knows that it has to tell the Plex server to mix down the audio. e.g. from a 5.1 audio track in the source file to 2.0 (stereo).

The Chromebooks don’t have 6 speakers in them. But “6” is the number of speakers they tell any Android app which is running on them. So you end up with the L and R channel from a 5.1 audio track.
And since all the dialog of a movie is usually in the Center channel and not in L or R, you end up with inaudible voices when playing a movie which has more than stereo audio track.

The only solution would be to force the app to stereo when a Chromebook hardware is detected.
But I don’t know if the Plex Android app can even do that.

[wpwentzell]

Hello Otto,

Thanks for your reply. You are indeed correct, and this has been noted by the ChromeOS devs, which is evidenced in this reply to the original bug report: 1125275 - chromium - An open-source project to help move the web forward. - Monorail

It seems there was a fix in place to downmix the audio from 6 channels to 4 channels, splitting the center channel evenly among the L & R channels. However, that was in ARC++. I believe that my device uses a different Android runtime, and this is likely why that fix does not apply to my (newer, x86, comet lake) device. I do think this can be handled a few ways: it can be handled via the original fix by the Chrome devs, porting to the latest Android runtime; or, it can be fixed by PLEX, requiring a forced stereo transcode when detecting ChromeOS hardware (if it can even be reliably detected, that is). Obviously. the former fix is preferable, but Google is known to drag their feet on simple, yet low priority, bugs such as these. I wanted to re-open this thread as this is still indeed an issue, and needs some resolution, either via PLEX or Google.