I am having audio/video sync problems while watching movies off my PC. I have my HP PC hooked up to a Samsung HT-X40 home theater system by a fiber optical cable. I also have my 32" LCD TV hooked up to my PC by a HDMI cable. As I first start to watch my movies on my TV and through the surround system everything is perfect. Then, gradually the audio starts to lag behind the video. It takes about 20-30 mins before it starts to get annoying enough to do something about, about 1-1.5 sec behind. The only way i can fix this is if I turn off the surround system and turn it back on. Then everything is perfect again...for 20-30 mins. Its annoying having to do this 3-4 time during a movie. What is causing this gradual sync loss? What can i do to fix this? Im up for any suggestions and any help will be appreciated. Thanks.


PC - HP m7750n AMD Athlon 64 x2 5000+ 2.6GHz
Sound Card - Turtle Beach RIVIERA 5.1 Channels 24-bit 48KHz
Video Card - NVIDIA GeForce 8600 GTS

Not one response? Anybody?

Ok, I'll take a shot...

Although we think of the audio and video streams from your pc as synchronously moving from disk to display and from disk to speaker, both of the processes are actually asynchronous, with packeted data moving from pc to tv and from pc to receiver -- and with processing taking place after receipt in the receiver and in the tv. When either the tv or the receiver completes processing a packet of data, it requests the next packet from your pc. Because the requests for audio(optical) and video(hdmi) data are not linked, they are satisfied, individually, on-demand, by data placed in (short!) output queues by a player application process that extracts the audio and video content (simultaneously) from the disk. [The operating system, and audio card driver are also involved here.]

But your tv is processing 'frames' of video faster than the receiver is processing 'frames' of audio. Eventually, the process stabilizes at a state in which the pc's audio output queue is full, and the video output queue is empty. Now whenever an audio+video frame is read from the disk, the video frame is passed 'immediately' [through the empty video output queue] to your tv, while the audio frame is added to the end of the completely full audio output queue, which is apparently at least 1.5 seconds of audio data in size. Consequently, your receiver is only just receiving/processing audio data placed in the output queue 1.5 seconds earlier! [Which explains your timing problem, I hope...]

Normally, you synchronize the audio+video flow rates by connecting the pc, receiver, and tv together, in sequence, by hdmi. Otherwise, you can 'solve' the problem by reducing the size of the audio output queue to a maximum allowed size of (say) one tenth of a second of audio data. This is a player application, audio card driver, and/or operating system software issue, but it will not be unique to you. I'd start by contacting the audio card driver support.

Very educated answer, i must say. Thanks for taking the time to respond. I will contact the audio card support service and take it from there. Ill keep posted. :)