VirtualDub documentation: FAQ

Here are some answers to questions I get asked way too often....

Basic questions

For more tips in general, see VirtualDub's online documentation.

Is VirtualDub compatible with Windows XP?

Yes -- in fact, both of my development platforms are now XP-based. All 32-bit x86 versions of Windows are supported except for Windows CE and versions of Windows NT prior to 4.0.

Previous versions used to have MP3 audio source support, VBR audio support, etc. How come the current versions don't?

No, they didn't. Some people have made unofficial modified versions in the past that did, but the official versions never had those features.

Is there an Athlon-optimized version?

No, and I have no plans to make one, as I don't have a compiler that specifically targets Athlon anyway. MMX, SSE, and SSE2 optimizations in the normal build will automatically kick in as appropriate on AMD CPUs.

Is there an AMD64 (x86-64) version?

Not yet. However, the current 32-bit versions run fine under 64-bit Windows.

Input/Output

Can VirtualDub read QuickTime, MPEG-2, RealMedia, or ASF files?

No, and installing codecs won't help.

Can VirtualDub write MPEG-1 files?

No, only read them. I don't have a desire to write an MPEG-1 encoder at this point.

What does "Packet sync error" mean? I get it when I try to open my MPEG file.

It means one of two possibilities:

• You have an MPEG-2 file, which VirtualDub doesn't support;
• You have an MPEG-1 file that is corrupted.

VirtualDub's MPEG-1 parser is intolerant to errors compared to its AVI parser, so unfortunately there is no easy solution to the latter problem.

56Kbps MP3 sucks. How do I get VirtualDub to encode 128Kbps MP3?

The MP3 encoding capability you're seeing isn't in VirtualDub -- it's being provided by an audio codec you have installed in your system. You need to install a better one to get higher bitrate support. And no, I won't tell you where to get one.

Editing

For more tips on capturing, see documentation on editing.

How come parts that I've deleted get stuck back in the file?

When editing in Direct video mode, there are some limitations on where cuts can occur. Specifically, you can only remove a non-key-frame (shows up as [ ] beside the timestamp window) if you also remove the frame before it. Essentially, any blocks of video you remove have to end right before a key frame (shows up as [K]), although they can begin anywhere. This rule is imposed by the way video is compressed. Whenever VirtualDub detects a violation of this rule it automatically adds in frames back to the previous key frame to fix the problem. There are no such restrictions when decompressing or recompressing a video stream.

Why do I get "Direct stream copy cannot be used with this video stream" errors when I try to edit my AVI file?

You don't actually have an AVI file -- you have an MPEG-1 file that has been renamed to have the .avi filename extension. MPEG-1 video data can't be streamed into an AVI file due to bidirectional motion prediction. VirtualDub ignores filename extensions when detecting the type of a file; for that matter, so do many players.

Why does VirtualDub freeze at frame 9995, 9997, etc. when compressing to MP3?

This is caused by the Creative Labs MP3 codec -- disable or lower its priority in the Multimedia control panel. Note that it is not a good idea to have more than MP3 codec installed as the Windows Audio Compression Manager doesn't distinguish between multiple codecs with the same format very well, and programs may not use the specific codec that you choose.

Capturing

For more tips on capturing, see documentation on capturing.

VirtualDub says it can't connect to my capture device...?

VirtualDub requires a Video for Windows (VFW) compatible device to capture video. Some newer devices are shipping with a Windows Driver Model (WDM) driver, that VFW programs can only use through a Microsoft conversion wrapper; this wrapper doesn't always work very well and generally can't cope with IEEE-1394 ("FireWire") devices at all, such as DV camcorders.