Problem with WMV file

farss wrote on 5/27/2003, 8:03 PM
I'm converting a number of .wmv files to PAL to go out on VHS. First one worked fine, even though it took 10 hour to render I know there's a lot of numbers to crunch.

Second file I've tried this on plays fine in WMP but when put on timeline all but first few frames are black, audio is fine. Tried pre rendering it but same result.

Both files are fro the same source so I imagine they were encoded the same.

Anyone had any experience with this problem?

Comments

kameronj wrote on 5/27/2003, 8:40 PM
I wouldn't assume both were encoded the same. I have seen this problem with the encoding of some files. However, I don't know off hand how you can tell what one is encoded with over the other.

Best to say this - if both worked or if both didn't, then I would assume they were encoded the same. Since one works and one doesn't....well, you can do the math from there.
SonyTSW wrote on 5/27/2003, 11:02 PM
Some WMV files have been encoded with very few keyframes (this is Windows Media terminology, not to be confused with Vegas keyframes). These keyframes are frames that are independent from other video frames in the video stream and are needed for random seeking.

If your WMV files have very few keyframes then you will have trouble incorporating them into your Vegas projects. I've come across some WMV files that had only one single keyframe, which was the very first frame in the file.

Vegas needs to do somewhat random seeking, in order to display thumbnails for the video frames in the events, in the media pool for the Thumnail view, in the trimmer if you've got the animate video frames in trimmer preference enabled, and so on. WMV files which have very few keyframes are likely to display black frames for these thumbnails and animations, and also will show black frames in the video preview window when you click the cursor around to different places in the timeline.

One simple test is to first start playing the WMV file in the Windows Media Player. While it is playing, drag and drop the seek cursor to another location. If it jumps only a few different locations (depending where you dropped it), or worse it always returns to where it is currently playing, then it is a good bet you are going to have trouble with that file in a Vegas project.

You may need to use the Windows Media Encoder to re-encode such WMV files so they have more keyframes for better seeking behavior in Vegas. Make sure the keyframe interval is set to several seconds or less (WME 9 defaults to 2). The encoder is a free download from Microsoft.
farss wrote on 5/28/2003, 2:07 AM
Thanks heaps for the advice, that makes perfect sense as the file was originaly only intended for streaming there would be no need for it to have any keyframes.

The other file consistently lost audio sync but was fine when rendered out as an AVI so I would imagine the lack of keyframes may have contributed to that as well.