Video Rotation in Virtual Dub 1.9.11

[vjmehra]

Hi,

Apologies if this is obvious, but I just can't work it out!

I have an avi file, that I open in Virtual Dub, this works fine.

I then go to Videl->Filters->Add

I select Rotate 2 with the following:

Rotation angle: -8.000 degrees
Filtering mode: Point sampling
Fill color: (Black)

I then click show preview and the video appears rotated as I'd expect.

However when I then go to File->Preview Filtered

It simply shows the original avi clip, without the rotation.

I can't find anything online, or in the help file...what am I doing wrong here?

[jagabo]

Preview Filtered works ok here with 1.10.3. By the way, point sampling is pretty crude. Bilinear or Bicubic looks much better.

[El Heggunte]

I then click show preview and the video appears rotated as I'd expect.

However when I then go to File->Preview Filtered

It simply shows the original avi clip, without the rotation.

Make sure that "View -> Output video pane" is ticked

[davexnet]

The "After" image should show up in the right pane:

[vjmehra]

Ah I feel quite stupid now!!!

The output video pane was ticked....however the other window was behind the first pane, which I stupidly didn't realise.

Thanks for the tips, especially on the sampling!

[vjmehra]

Hmm, although one question I do have...

Would the audio get affected by adding a rotation somehow (I can't see why it would....but in short it has, the original file audio is fine, viewing the second one its not, very odd)?

[jagabo]

Would the audio get affected by adding a rotation somehow (I can't see why it would....but in short it has, the original file audio is fine, viewing the second one its not, very odd)?

The audio isn't effected by video filtering. But VirtualDub sometimes has problems with audio. Did it give you any warnings when you opened the original file?

[vjmehra]

No warnings and if I just play the original file (without the filter) the audio seems fine...

[jagabo]

What exactly is wrong with the audio in the new file? When you made the file, did you leave VirtualDub's audio setting to Direct Stream Copy?

[vjmehra]

The audio sounds like its cutting out every frame if that makes sense, so its almost like a fraction of the sound is trimmed at the end of each frame, so everything is disjointed (sorry that's vague, not entirely sure how to explain it).

Yes I left Direct stream copy checked, should I not do this?

[jagabo]

I guess this is one of those occasions where VirtualDub messed up with the audio. Normally you want to use Direct Stream Copy mode so the audio is just copied from the original file to the new file. I guess you can try Full Processing mode and recompress the audio (or leave it uncompressed PCM). Or maybe remuxing with AviDemux.

[vjmehra]

Hmm, well I think there may be more to it than that...when I try to export it (save as AVI and/or save as old format AVI) the video is all jerky and slow, the audio still doesn't work properly.

If I playback the filtered video in the program, the audio is messed up, but at least the video is smooth.

Am I exporting/saving it in the wrong way, is there perhaps an alternative setting I should use?

[jagabo]

What video codec are you using? If you're saving as uncompressed RGB you will have a very large file and your hard drive is probably too slow to get smooth playback.

[El Heggunte]

jagabo is much faster than I =^.^=

[vjmehra]

I guess whatever the default is, I haven't selected anything in particular, I simply try to save the file, but yes you are correct it grows insanely large very quickly!!!

[jagabo]

The default is uncompressed RGB. You need to reencode with a video codec to get files that will play smoothly on your computer.

[vjmehra]

So does that mean I need to get some kind of 3rd party app, or can this be done within VirtualDub?

[jagabo]

VirtualDub: Video -> Compression... pick a codec and configure it. I suggest you use Xvid or Divx. If you don't have them, download and install the Xvid codec.

[vjmehra]

Ah that helps...

However the video seems to run smoothly for a few frames (which it didn't before), but then goes jerky for a frame or two, then smooth, then jerky and so on (I was using the 'Go Pro-CineForm Codec v8.6.3 as I had it installed).

Will a different codec be likely to make a difference, or could there be something else wrong?

[jagabo]

I suspect the problem is decoding the original source video, not the encoding of the new video. But try opening the new video in VirtualDub and stepping through frame by frame with the right arrow key. Do you get smooth steps when there is motion? Or do you get many repeated frames at times?

[El Heggunte]

[ ..... ]

[vjmehra]

I don't seem to get any repeated frames, it seems to be smooth when going through frame by frame.

I tried using one of the included codecs...the quality is awful, but it does work (i.e. the frame rate is smooth and the audio works), so I guess that probably is the issue, I will try the xvid codec as suggested.

[vjmehra]

I do have one more question though...is it possible to do the rotation and then crop this, without having to first save the avi (as obviously this takes ages)?

Currently I would have to rotate, save the file as an avi, re-load Virtual Dub, do a new rotate filter of 0 degree's, but crop the video as part of this filter.

I'm sure there is a better way than that, but I can't seem to work it out if there is!

[jagabo]

You do it all at once. Add the Null Transform filter after rotation. Apply Cropping to the Null Transform filter. In VirtualDub, when you apply Cropping to a filter, the cropping takes place before the filter. Null Transform is a "do nothing" filter.

[vjmehra]

Ah yes, I see what you mean! Basic, didn't realise you could do that, ha! Great thank you! Hopefully having downloaded the codec I'm all set now!

[pandy]

Preview Filtered works ok here with 1.10.3. By the way, point sampling is pretty crude. Bilinear or Bicubic looks much better.

I agree - additionally video before rotation can be enlarged (200 - 400 - 800 - 1600% at least - more - better but processing time and memory requirements grows - however point sampling algorithm can be used for this), after rotation image shall be resized back ie same factor as enlarged with decent resampling algorithm (at least bicubic).