firefox audio / youtube crashes?

[Gary Aitken]

I think I should know this but I don't, and a search didn't turn up anything
recent.

It's my understanding firefox 22 with html5 should allow playing youtube videos
without the flash plugin.  But when I try to watch a youtube video, firefox
crashes.  I had this working on firefox 17 under 9.0 but don't know how it was
configured...  My firefox is installed with the following options:  

/usr/ports/www/firefox$ make showconfig
===> The following configuration options are available for firefox-22.0,1:
     DBUS=on: D-Bus IPC system support
     DEBUG=off: Install debug symbols
     GCONF=off: GConf configuration backend support
     GIO=on: GIO for file I/O
     GNOMEUI=off: libgnomeui support module
     GNOMEVFS2=off: GnomeVFS2 (virtual file system) support
     GSTREAMER=off: Multimedia support via GStreamer
     LIBPROXY=off: Proxy support via libproxy
     LOGGING=on: Additional log messages
     OPTIMIZED_CFLAGS=off: Use extra compiler optimizations
     PGO=off: Use Profile-Guided Optimization
     WEBRTC=on: Web Real-Time Communication
====> Options available for the single AUDIO: you have to select exactly one of them
     ALSA=on: ALSA audio architecture support
     PULSEAUDIO=off: PulseAudio sound server support

I installed the following as freshports indicated they were needed to run,
but it made no difference:
    www/nspluginwrapper
    audio/alsa-lib
    multimedia/libv4l

hints?