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Unofficial VirtualDub Support Forums > Testing / Bug Reports > 1.5.1 Image Sequence Bug


Posted by: Morsa Feb 23 2003, 03:18 AM
The bug is this.
I use Vdub latest version (1.5.1).I open a video, select framerate 24 fps, selct compression Mainconcept DV codec or DIVX.
I choose to save an image sequence.The saved images are empty.
I open this corrupted sequence with Vdub and I see only pure black frames.
The files have only between 16 and 1 K sizes.

Can anyone reproduce this bug?


The same problem applyes to Vdub 1.5.0 and 1.5.1
I don't know when it started cause I remember older versions didn't have this behaviour.
Try it and you'll see it.

Posted by: fccHandler Feb 23 2003, 04:04 AM
Yes, I reproduced it. I don't have the DV codec but if I save a BMP image sequence with compression = DivX codec, the BMPs actually contain DivX-compressed content. I don't know if it's a bug or a feature (it's actually kinda cool...)

Just use "uncompressed" for your image sequences and you'll be fine.

Posted by: phaeron Feb 23 2003, 11:07 PM
All versions do this. VFW provides ICImageCompress() and ICImageDecompress() functions to use video codecs to compress and decompress images, and the original intention was that you could use certain codecs to save compressed BMPs. Well, it turns out that RLE in AVI is slightly different than RLE in BMP, and no programs bothered to implement BMPs compressed with codecs, so this is less than useful.

Posted by: Morsa Feb 24 2003, 06:06 AM
But when I re-open the image sequence with Vdub I can see nothing.I guess it is supoosed that if this is the case Vdub could open the sequence.
Am I right?

Posted by: fccHandler Feb 24 2003, 06:11 AM
QUOTE (phaeron @ Feb 23 2003, 07:07 PM)
... it turns out that RLE in AVI is slightly different than RLE in BMP

Hmm... I remember a very long time ago trying to write a QuickBASIC program to convert 8-bit FLI files into AVIs with RLE compression (thinking that the conversion could be lossless) and I never got it to work properly. I know exactly how RLE works in BMPs, but how is the ICM codec different?

Posted by: phaeron Feb 25 2003, 03:14 AM
I don't remember the difference offhand, but I do remember it being subtle -- something like BI_RLE requires word alignment but AVI RLE doesn't, or something like that.

Posted by: fccHandler Feb 25 2003, 04:03 AM
laugh.gif I'm actually glad that you don't remember, as I truly didn't relish the thought of digging through ancient backups to find that sorry proggy and my FLI files...

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