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Discussion Starter · #1 ·
I've narrowed down the problem I've been having with audio. I have an Audiophile 2496 sending audio via SPDIF (coax) to my reciever. In both PowerDVD and Zoom Player (with AC3Filter audio) when I play a VOB file (48Khz) it works fine. I then play an AVI file (44.1Khz) and the audio can't be heard. The monitor shows the levels moving, but no sound to be heard. If I change the Master Clock from Xtal to S/PDIF and back to Xtal, the sound plays. The Codec Sample Rate shows that the rate does change from 48 to 44.1. Note that if I play the 44Khz first, and then the 48Khz, it switches fine and both have audio. I'm using the 5031 driver, though the problem also occurred with the 5027 driver. Can anyone test this to confirm theirs either behaves the same, or is it just me? Here are links to to sample files:

48.vob

This is a 32MB vob file in Dolby Digital at 48Khz

44.avi

This is a 2.5MB video capture at 44Khz


Play the 48Khz first, then play the 44Khz.
 

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I don't really know if its a "bug", it might have a use... somewhere... But apprently when whatever DVD program you use, goes to play a DVD, it changes your spdif output from consumer to professional. To fix it just go under the spdif tap and change it back to consumer.
 

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Discussion Starter · #3 ·
The 'Consumer/Professional' setting doesn't seem to change at all. In reading the Zoom Player website, I stumbled across the following:

Quote:
The problems with DirectShow rendering SP/DIF sync issues with cards like the Delta DiO are believed to be due to a bug in the Microsoft WavePCI model for WDM audio drivers. Other audio drivers from Creative, Turtle beach, ESS etc. all use WaveCyclical WDM driver model which does not have the problem.


Basically, the problem is that WDM drivers that are built using the WavePCI model (like M-Audio's WDM drivers) have thier buffer positions lost when reporting up the WDM stack. The over all affect in DirectShow is that the IReferenceClock host (in DShow DVD is always the Audio Rendering filter) races forward each time an audio stream has discontinuities from doing things like navigating the DVD (chapter forward, menu selections, etc..)


All DirectShow audio decoders will have this synch problem with the M-Audio drivers when connected up to SP/DIF with WaveFormatTag 0x92 (the standard AC3_SPDIFPASSTHROUGH format tag).


Please note that on Win98, M-Audio uses a VXD based driver (not WDM) and the VXD based driver does not suffer this percieved bug in the Microsoft WDM archeteture.


To remedy the problem, M-Audio is going to write an entirely new WaveCyclical WDM driver to accomidate DirectShow usage. The schedule for this driver is not known, but M-Audio says that they are going to do it.


So to recap, All M-Audio WDM mini drivers based on the current WavePCI model will have sync issues in DirectShow. This synch issue is eliminated when using the M-Audio WaveCyclical WDM drivers.
I don't understand what any of this means. Anyone understand this and whether it explains my problem?
 
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