CamStudio, keyframes, and virtualdub

[photonbuddy]

Hi All,

I am working on a DVD for a client to aid his staff members using a new PC system.

I am doing various tasks, and capturing them using CamStudio, and DivX 6.2 as the codec.

The quality of the produced video is more than acceptable, but I am having a problem editing the final video.

I have CamStudio set to set a keyfram every 25 frames, but when I load the video into virtualdub, keyframes seem to be all over the place.

This means editing the video is next to useless, as virtualdub puts back-in all the frams I remove because of the keyframes.

I did some reading, and it was suggested that this was a by-product of using direct stream copy mode, so I changed to full processing mode, but had the same problem.

Can anyone suggest a way to have more closely spaced keyframes to allow finer editing in virtualdub?

Any help is much appreciated.

[jagabo]

When capturing with Divx keyframes will be inserted any time the Keyframe Threshold (difference between frames)is exceeded. In addition there should be one keyframe at least every Keyframe Interval. So if you set Keyframe Interval to 25 there should be at least one keyframe every 25 frames, and often more when there are abrupt changes in the video.

Working with a PAL source, with Keyframe Interval set to 25, you should have a keyframe at least every second.

You could set Keyframe Interval to 1. That will make all frames keyframes. The file size will go way up if you are using constant quaity encoding, or video quality will go down if you're using constant bitrate encoding.

VirtualDub in Video -> Full Processing Mode should allow you to cut on any frame. In this mode the video is fully decoded to RGB, manipulated (filtered, trimmed etc), then compressed (you have to select an ouput codec).

I haven't used it, but the latest version of VirtualDub has a smart rendering feature. This uses Direct Stream Copy mode whenever it can, but recompresses any sections it needs to (around your cuts).

[photonbuddy]

When capturing with Divx keyframes will be inserted any time the Keyframe Threshold (difference between frames)is exceeded. In addition there should be one keyframe at least every Keyframe Interval. So if you set Keyframe Interval to 25 there should be at least one keyframe every 25 frames, and often more when there are abrupt changes in the video.

You could set Keyframe Interval to 1. That will make all frames keyframes. The file size will go way up if you are using constant quaity encoding, or video quality will go down if you're using constant bitrate encoding.

I tried setting it to an interval of 1, however, it still failed to insert any keyframes (apart from the first one) in a 20 second test capture.

Would keyframes be generated by DivX or CamStudio?

[jagabo]

Keyframes are created by the codec.

Are you using the free version? Maybe the free version ignores the keyframe interval?

[photonbuddy]

I'm using DivX Pro. Maybe I should try a different codec.

[jagabo]

Are you configuring Divx from withing CamStudio? I don't see why the keyframe setting wouldn't work. Some things you might check:

Certification Profile: Unconstrained
Encoding Presets: Off
Rate Control Mode: 1-pass quality based, quantizer~3
Encoding Mode: Fastest (or whatever your computer can keep up with)
Bidirectional Encoding: Off
Max Keyframe Interval: 1
Quarter Pixel Search: Off
Global Motion Compensation: Off

HuffYUV is good (fast) for video capture but doesn't give high compression. PicVideo Motion JPEG is fast and can give higher compression.

[photonbuddy]

Are you configuring Divx from withing CamStudio? I don't see why the keyframe setting wouldn't work.

Yes I am configuring from within CamStudio.

Some things you might check:

Certification Profile: Unconstrained
Encoding Presets: Off
Rate Control Mode: 1-pass quality based, quantizer~3
Encoding Mode: Fastest (or whatever your computer can keep up with)
Bidirectional Encoding: Off
Max Keyframe Interval: 1
Quarter Pixel Search: Off
Global Motion Compensation: Off

Ahhhh ... I am sure I turned off encoding presets and checked the codec tab, but I must not have. Either that or downloading v6.5 of the codec fixed something.

Turning off encoding presets has un-grey'd all the values on the codec page.

Thanks so much to all that have made suggestions in this thread, especially jagabo. Much appreciated.

[jagabo]

Ahhhh ... I am sure I turned off encoding presets and checked the codec tab, but I must not have. Either that or downloading v6.5 of the codec fixed something.

Turning off encoding presets has un-grey'd all the values on the codec page.

Glad to help out. I wasn't sure if turning off presets would help but I threw it out as a possibility. I never use the presets! Well, you got it working one way or another.

[BJ_M]

if you plan on editing the captures = you should not use divx, which isnt really an edit format

[jagabo]

Divx is pretty much the same as MJPEG if you use all keyframes.

[DarrellS]

I believe DV, MJPEG and Lossless compression all have every frame a keyframe.

I have always been told that it is best to capture in one of these formats and then edit and compress to final format, DivX 6.2?

Using Jagabo's instructions though, you can capture DivX with all keyframes or every other frame. I've never captured with DivX on my machine but I suppose if your machine is fast enough that you should be able to capture without lost frames or sync issues and then cut on keyframes and direct stream copy to get the same results.

I know my brother's PC has an ATI card that captures in DivX format but I haven't tried it.

[photonbuddy]

Using Jagabo's instructions though, you can capture DivX with all keyframes or every other frame. I've never captured with DivX on my machine but I suppose if your machine is fast enough that you should be able to capture without lost frames or sync issues and then cut on keyframes and direct stream copy to get the same results.

I have a reasonablly fast PC (Intel Core2Duo e6400 overclocked), so the capture process runs at just under 20fps, which is fine for what I am needing it for. If I was capturing a movie, or other hi-motion format, then I'd have a re-think.

There's no audio, so sync problems aren't an issue either.

I ended up setting ketframes to every 10 frames, as I didn't need the accuracy of frame-by-frame editing.

Once again, thanks for the input