hi, I have the following setup:

i5 3570k @ 3.4 ghz

8.00 GB ram

Graphics Card

MSI HD7950 PCIe card, no overclocking

AMD Catalyst Driver Version, and Driver History
on 12.10, tested 12.4 and 12.6, issue only exists on versions after 12.4
Operating System
win7 home premium 64bit

Issue Details
after upgradig from version 12.4 catalyst, the hdmi pcm signal that goes via hdmi to my hifi (and then frm there to my hdtv), cuts out intermittantly every few seconds for a half second or so, stopping all audio. video output through the hifi to the tv during this is unaffected.. I can see on the hifi that the pcm signal has stopped, and when i downgrade drivers to versionn 12.4 then the issue completely disappears.

the issue is normally occuring when just on windows desktop and playing some music etc. Since the whole pcm output cuts out, when on windows desktop all programs are affected at once.  However, When I run an application that is in full screen, eg xbmc media player or a pc video game, the issue disappears.

Also if i change the pcm sampling frequency output in windows sound settings, say from its current setting of 96khz, if i change it higher then the intermittant cutout happens more often, with higher frequency, and less with lower frequencys of samplig. no sampling setting eliminates the issue.

Motherboard or System Make & Model
asus p8z77v lx

Power Supply
unknown, can get if important

Display Device(s) and Connection(s) Used
connected by hdmi to a pioneer vx921 hifi, which is connected by  hdmi to a toshiba zl800 hdtv, with pcm sound beng decoded and output on the hifi before it gets to tv.

Applications and Games
- list out all applications and games where the issue is occurring
- include details about version or patch numbers

CPU Details
i5 3570 at 3.4 ghz, no overclocking
Motherboard BIOS Version
unknown, can getif impportant
System Memory Type & Amount
-corsair vengeance 2x4gb kit, so 8gb total

Additional Hardware
no other cards installed, i.e. nothing at all installed in the other pcie slots.

Additional Details
issues all disappear on catalyst version 12.4 when i downgrade, as soon as i go on a later version then intermittant sound issue returns.

I'm in the same boat, but I have found a workaround that might also help identify the source of the problem; please see issue details below.

Graphics Card:
 -XFX HD7950 (FX-795A-TDFC)

AMD Catalyst Driver Version:
 -Currently using 12.11 Beta
 -Issue was also present in 12.10 

Operating System:
 -Windows 7 SP1 64-bit, all updates applied.

Issue Details:

 When not gaming, audio output over HDMI cuts in and out, mostly out. For every 3-4 seconds of silence there will be normal sound output for about half a second.

 As soon as I start a game (Skyrim in the present case) the sound performs normally for the duration of the gaming session, then returns to the problematic state when the game is ended.

I haven't yet tried rolling back to much earlier driver versions as the previous poster reports.

-WORKAROUNDS-

Some additional research I did led to the following; unfortunately I've lost track of where I cobbled all the information together that got me to try these things, so apologies to anyone who deserves credit for these discoveries.

1. By enabling then disabling the LCD Overdrive feature in the Catalyst Control Center (under My Digital Flat-Panels) the problem will be resolved until the system is restarted.

2. By increasing the 2D clocks with a manually modified preset (instructions found here: http://www.techpowerup.com/forums/showthread.php?t=117633 ) the sound problem would be resolved entirely, but this also introduced some instability into my system so I stopped using this method. I don't recall exactly what levels I increased the clocks to (though I tried to be conservative), so it's possible there's another value that would have resolved the problem without introducing instability.

Motherboard:
 -MSI Z77A-GD65

Power Supply:
 -650 Watt, XFX XXX Edition P1-650X-CAG9 

Display Device:
 -Vizio M370SL HDTV connected with HDMI

CPU: 
 -i7 3770K @ 3.5 ghz

Motherboard BIOS Version:
 -10.7 (latest)

System Memory:
 -8gb (2x4gb) G.Skill Sniper DDR3-1600 

Additional Hardware:
 -Mushkin Chronos Deluxe 240GB SSD for boot and games
 -2TB RAID5 (3x1GB HDD) through integrated Intel controller

Additional Details:

 Issue was also present with a previous motherboard/CPU combo, and HD has been wiped and OS reinstalled with no effect on the issue.