| Printable Version of Topic
Click here to view this topic in its original format |
| Unofficial VirtualDub Support Forums > Testing / Bug Reports > Resize Corrupting Graphics |
| Posted by: i2mc Jul 8 2003, 11:28 PM |
| Hi My problem (which I believe is a bug) is as follows; I have a standard set of filters I automatically apply to clips, I've started noticing problems with bold captions as follows; I start with a white (not 100%) on black caption which is 720 x 576 Filter 1 is de-interlace Filter 2 is resize to 352 x 288 (standard PAL MPEG1 size) The preview shows fine, but the actual AVI produced (using MPEG4 V2 codec) exhibits blocky corruptions - kind of as if some macro blocks are being put in the wrong place. If I resize to 360 x 288 (the neat division by 2) the problem seems to go away. I've tried various options on the resize such as bilinear / bicubic etc but all that does is move the corrupt blocks to a different part of the screen. Also, I've tried cropping the image as well and it causes really weird things to happen - for example the caption shifts maybe 1/3rd of the way across the screen and wraps around to the start again. I've posted a before and after processing image to show what the fault looks like. http://www.moffatt.uk.net/vdubfault.gif Any thoughts? Thanks Roger PS. Version in use is VirtualDubMod_1_5_1_1a, system runs XP home with windows media player 9. |
| Posted by: fccHandler Jul 9 2003, 12:26 AM |
| Ah, I know it well. This is not a fault with VirtualDub, it's a known fault of the MS MPEG4 codecs. Pardon my language, but the technical term for it is "shit." IIRC Nandub had an "anti-shit" checkbox that was supposed to correct exactly this artifact. It mostly occurs in high-contrast areas (like credits) and the general belief is that it's caused by an overflow error in the codec. It can also be seen in the DivX ;-) hacked codecs. I recommend upgrading to the latest http://www.divx.com/divx/. |
| Posted by: i2mc Jul 9 2003, 12:00 PM | ||
Many thanks for the speedy reply :-) I actually end up coding MPEG1 and MPEG2 and was just using the MPEG4 as an intermediate codec for the deinterlaced AVI to help out on disk space. It seemed like a good idea at the time ... I'll swap codecs Thanx Again Roger |
| Posted by: fccHandler Jul 9 2003, 05:30 PM |
| Depending on the MPEG encoder, you might be able to frameserve VirtualDub's output and avoid using an intermediate file. I know this works great with TMPGEnc (not sure about other encoders). |