Author Topic: Audio Sync Drift  (Read 2332 times)

January 07, 2010, 03:27:55 AM
Read 2332 times

philait

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Hi,
I've had a V2 WDTV (firmware 1.01.75) Since Christmas, I've ripped all of my DVD's to ISO and now am starting to convert these to MKV to claim back some of the 1.5TB of disk space they are taking up.

My Sources are PAL DVD and I'm using Handbrake 0.94** for the conversion.
Audio and video start out in sync perfectly but after time they drift apart. I don't believe it's the encode in fact I'm sure of such as stopping and starting the MKV using resume and the Audio is again in sync. Playing with VLC/Media Player Classic or WMP and the Audio stays in sync.

I'm also going to try some re-rips with constant Frame rate in Handbrake instead of the VFR default, I'm not convinced this is the entire cause though as an Xvid AVI of Zombieland was slipping out of sync too this was CFR 25fps as far as I could tell.



**I'm using Handbrake mainly because it's excellent foreign audio search for subtitles cops very well with a the large amount of multi lingual Audio I have on my collection. I've tried other tools but they can't seem to cope with only ripping forced subs without more awkward steps of sub extraction and re-encoding.

January 07, 2010, 12:15:11 PM
Reply #1

philait

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OK Here's the latest on this.

ALL DTS Passthrough Play fine and perfectly in sync 100% of the time.

Any AC3 passthrough 5.1 discreet or 2 channel ProLogic start off in sync and within 10-15 minutes are at least half a second out. Stopping and resuming fixes the issue for while but it comes back again.

Some people have stated that switching the Audio Output from Digital (I'm using a HDMI AV AMP) to Stereo fixes this issue it doesn't (for me anyway).

It has also been claimed that using the Same as Source setting for Framerate in Handbrake (This sets the Variable Frame Rate flag in the file) is the cause and switching to a  CFR Fixes the issue it doesn't it only lessens the issue the Audio still drifts just by a smaller amount which is less noticable.


Given that VFR and DTS works fine but CFR or VFR with AC3 shows the issue in varying amounts surely there must be a Firmware bug in the sync of AC3 streams?