[fixed] WMV sync problem (was: Re: Latency When Recording)

[Jakob Rubenson]

Hi

I´m trying to post this in the right thread. We have a pretty good setup with a I7 920 and Vista 32 bit using an Osprey 450 for both sound and video.
Analog video and audio from different cameras.

We have a problem with the audio being 5 frame out of sync from the video when we save as WMV and open the file in our editing suit. When we open the file in our post production software (we use Sony Vegas Video on a PC) the audio is 5 frames off. But, if we play the same WMV-file in mediaplayer, the material is in sync.

If we save as MOV the material is in sync.

My guess is that Vidblaster has a bug regarding saving as WMV and that WMV has some kind of sync system built in that corrects the problem when playing the file.

We use the WMV file to add top and tails and then encode to flash. The end result is a file with the audio 5 frames off.

Here are my testfiles:
informationdesign.se/vidblaster/

And here is a screenshot that tries to explain the problem:

[Daniel Lill]

Jakob

Before you hit save after a recording in VidBlaster, its saves a file to C:\Users\[YourProfileName]\AppData\Local\Temp\CombiTech\VidBlaster

Make a copy of that wmv file and see if that is off-sync also...

And if its not... then its the save function thats has a bug...

[Jakob Rubenson]

The WMV in the tempfile is identical to the wmv created when saving. It´s actually a copy of that file.

SO:
My system generates a WMV with the sound 5 frames ahead of the video.
When this file is viewed in vidblaster or in mediaplayer/vls the sync is corrected.
When saving to Quicktime it´s also corrected.

Anyone?

Lill: can you make a test and see what your wmv:s look like?

JAKOB

[Mike]

Actually all files are encoded from the WMV master, so there should not be any sync differences. I have noticed though that there is a sync difference when I view the WMV in WMP from the start, or after pausing or seeking it. Maybe your editor shows the same problem. I do not know if this is an intrinsic problem of WMV coding, a bug in WMP, or even in specific WME versionsor how VidBlaster addresses it. Whatever it is, VidBlaster's encoders do not seem to have the problem. I have yet to do research on this.

As I mentioned here, v1.09 has some changes in WMV recording so I suggest waiting for that release before continuing this thread. Just in case.

[Jakob Rubenson]

Just to be clear. My examples are:

1. the WMV-file recorded with Vidblaster.
2. a quicktime file encoded from this WMV-file in Vidblaster.

I record and save first a WMV and then a Quicktime.

The Quicktime is ok. The WMV is 5 frames off for the entire file. This is always the case for the whole file (we often record up to 90 minutes).

We love the program and use it every week to record events. We will also use it to stream live.
Until this is fixed we fix the sync-problem in post production before we encode to flash.

I´ll try 1.9 but will not use any non-released versons at work. :-)

[Jakob Rubenson]

Mike

I know you´re looking at recording now.

Alain sent me a short testfile from his system (specs below). He has the same kind of file I have.
File plays well in VLC and Mediaplayer. Audio 5 frames off when editing.

If you like you can send me a WMV-file that I can put in my editing suit.

JAKOB

Alains spec:
VidBlaster 1.09 (320x240@30fps)
-Dell XPS 630 Core2Quad 8200
-ATI 4750 512MB
- 4GB RAM
- XPSP3
- Osprey-450e
- USB Mixer (MobilePre USB)
- 1 Sony SR-47 camcorder connected to Osprey 450e
- USB mixer output connected to Osprey 450e audio breakout cable

Edit: Changed seconds to frames.

[Mike]

I split up this thread and created a new one here.

I think we have it fixed in v1.10. See this recording. I see no difference when playing from the start or from some offset position. Can anyone confirm?

[Jakob Rubenson]

Mike

It plays well in VLC but the sound looks 5 frames off in editing (both on Mac and a PC).
I´m not sure.
Can you give me some material that´s easier to check (like a person speaking on cam).

JAKOB

[Mike]

I simply test it in WMP, like I described earlier in this topic. This video is actually easier to check than a person speaking, the white flashes and sound fx are now in perfect sync when played in VidBlaster, Real Player and in WMP both with and without offset. Are you sure you are not looking at a bug in your editing software? Are you sure you are using the standard Windows codecs to play this?

[Jakob Rubenson]

I need to do some more checking on my Mac. On my PC the video plays perfect but is out of sync while editing.

I have not seen that in any other material than from Vidblaster.

I´ll get back to you when I´ve tried it on three different machines and different editing softwares.

JAKOB