No audio on some YouTube videos

I have found that there are certain YouTube videos that play but there is no audio — as an example,

. I first noticed this on openSUSE 13.2 but it continues with Leap and occurs on both Chrome and Firefox. I have installed the multimedia codecs from packman but I wonder if there are other codecs which are not routinely installed but are available and might remedy this.
Incidentally the video noted above plays with audio when run from IE in a Windows 7 virtual machine.

Check the volume levels of the flash window??

Use the html5 options??

Actually, I just discovered the problem. I have a custom “daemon.conf” in ~/.config/pulse that among other things includes the line “enable-remixing = no” (the default is yes). When I comment out this line and no others the audio plays fine. Doesn’t make much sense to me.