Firefox needs media-plugins/alsa-plugins[pulseaudio] for <audio> and <video> to work properly with Pulseaudio, i.e. request for the following to be added: pulseaudio? ( media-plugins/alsa-plugins[pulseaudio] ) Reproducible: Always Steps to Reproduce: 1. Play audio from <audio> or <video> Actual Results: Ears start to bleed. Notice that no audio is played if Pulseaudio is already "active". If audio plays, notice that audio playback doesn't work for other applications. Also, control of volume is not possible through Pulseaudio. Expected Results: Use Pulseaudio for playback.
USE flags that only pull in other packages are useless and only cause dependency hell. It's really up to the user to install and set alsa-plugins properly up.