Pulse

If you have spent days and days fucking around trying to get sound to work with your NVidia 220GT HDMI, you have to use hw:0,7 not hw:0,3 which is the first thing pulse sees, and you need to unmute it in ALSA.

sudo apt-get install alsamixergui

Run alsamixergui and UNMUTE ALL FOUR FUCKING SPDIF CHANNELS.

Support for 24 bit 96 kHz audio

Make Pulse use 32 bit samples in /etc/pulse/daemon.conf and bump up the sample rate:

default-sample-format = s32le
default-sample-rate = 96000

Surround sound

Since I have a surround HDMI amplifier, I use this in /etc/pulse/default.pa after the autodetect phase (which you might still want for when you plug in USB devices, for instance):

load-module module-alsa-sink device=hw:0,7 channels=6 \
  channel_map=front-left,front-right,rear-left,rear-right,front-center,lfe

and in /etc/pulse/daemon.conf you need:

default-sample-channels = 6
default-channel-map = front-left,front-right,rear-left,rear-right,front-center,lfe

Dolby Digital and DTS "pass-through" streaming

There isn't currently a way to pipe the Dolby Digital or DTS streams directly to the amplifier without abandoning Pulse altogether and reverting to ALSA. However, these days decoding even 24/96 surround in Pulse uses pretty negligible CPU, and even when using ALSA it blocks the audio device. It also means you can enjoy all those annoying alarms, random pop-up beeps and messaging alerts while you watch your movies.