Dale, do you have multi speakers can repro this bug? 

=> chcunningham who was looking at another play movies issue. +ddorwin for play movies contact.

aig, does the player and/or this title support 5.1 audio on the web? If so, what format?

AAC 5.1 only. If the receiver requires Dolby Digital/DD+ or DTS then we don't support that yet.

Many receivers don't support AAC 5.1 so that is the most likely issue.

domholmes@, can you provide more info about your receiver? Do you know if it supports AAC 5.1?

aig@, this is a good caveat to add to the "supporting 5.1 audio" claims if its not already mentioned. Do you know where this support is described?

"Do you know if it supports AAC 5.1?"

While it supports playback of AAC encoded files; it doesn't seem to support AAC over HDMI. My receiver sees 2.0 PCM in these instances - is that being derived from the 5.1 AAC or is it a separate audio track? Would multi-channel PCM output be possible here?

Thanks for looking into it.

HDMI generally doesn't have enough bandwidth to support AAC 5.1 - in fact I'm not sure if regular HDMI can even support some of the pass-through codecs like DD+. You need HDMI ARC for that.

My previous post was slightly incorrect. The receiver sees PCM in whatever format Windows is configured as, in this case 5.1 - just with no audio from the rears. I'm guessing my audio driver is converting 5.1 AAC to 5.1 PCM? 

The Windows audio device properties for my card list the various Dolby/DTS and PCM formats but not AAC under 'supported formats'.

I highly doubt it's conversion. More likely the device is just not advertising support for aac51 as a codec, so the player is using stereo instead.

If you can capture a network trace (or even just the URLs) then I could tell you which streams it's actually using.

"I highly doubt it's conversion"

Something is converting the AAC to PCM, I imagine it's Chrome doing this. Can Chrome not convert the 5.1 AAC into 5.1 PCM, instead of 2.0? I believe this is what a Chromecast does with Play Movies over HDMI. AAC is not listed against the HDMI spec on wikipedia so I'm assuming it's not going to work with any receiver and multi-channel PCM conversion is the only option. 

I think what you want is to go to chrome://flags and enable "try supported channel layouts" -- this can't be enabled for everyone as it hard locks some users machines, but it will allow you stereo->multichannel expansion.

I have tried the 'supported channel layout' flags before. It didn't seem to do anything.

Regarding comment 10, I think there's a misunderstanding. It's not a question of whether or not the conversion is supported, it's a question of what the browser *advertises*. If Chrome doesn't claim to support aac51 as a codec (via the canPlayType API) then the player is not going to request surround audio and not going to send surround audio to MSE.

That's why I asked for a network capture or a list of request URLs; it will be pretty obvious from that list whether or not the player is even trying to play 5.1.

How would I retrieve the request URLs? The only surround content I have is paid for movies in my Play library. Or those I've rented.

You can get them from the network tab in Chrome dev tools.

I get a series of very large urls when playing back a video from my  Play library.

https://r8---sn-8pgbpohxqp5-aig6.googlevideo.com/videoplayback/id/987d3bbdc0fcd8d2/itag/223/source/youtube/cmbypass/yes/ratebypass/yes/hightc/yes/pfa/5/pbr/yes/gir/yes/clen/1447117693/lmt/1459109940946879/dur/6257.583/ctier/A/ip/82.47.64.66/ipbits/0/expire/1469155205/sparams/clen,cmbypass,ctier,dur,expire,gir,hightc,id,ip,ipbits,itag,lmt,mm,mn,ms,mv,pbr,pcm2cms,pfa,pl,ratebypass,source/signature/40B19F47854EC32DB3D0ED9654960A3C6BE2EB3A.64F7AF947F1654547AB41FA1B51D0BFBE41055AA/key/cms1/keepalive/yes/alr/yes/cpn/uDeXvLvzZSmu0vgb/cms_redirect/yes/mm/31/mn/sn-8pgbpohxqp5-aig6/ms/au/mt/1469126172/mv/m/pcm2cms/yes/pl/22?range=43597431-45116136

Yes, they're long URLs and that's fine. Unfortunately the one you've posted is a video URL, not an audio URL, so it doesn't help (the important part is "itag/223"). Can you post a few more of them?

Related to https://bugs.chromium.org/p/chromium/issues/detail?id=580899