VD cropping and video size

[papilio]

Hello,

Using VD, I'm trying to crop a roughly 1900x1100 video, with about 100 off the bottom and 4 off the rest.

The input file is about 5GB, the cropped output file size is about 32GB Fraps compressed, 18GB changing to YV12. No other filters or change in frame rate. Any ideas what's going on here?

Thanks,
papilio

[Guest]

What is the input compression codec and what did you use for compression on output?

[papilio]

Hi neuron2,

I had been using the default (no compression) all the way through, including the crop -- specifically, both the input file (30fps, 5GB) and the output file (50GB, down to 18GB changing from Fraps compression to helix YV12 for size reduction) -- both processed without changing anything but decimate by 4 only on the first, changed to crop (sometimes adding YV12) only on the second.

I've checked for any other (missed) differences quite a few times, can't find anything. I must have missed something anyway, but I've done the sequence quite a few times before, and to the best of my knowledge (I think I would have noticed something so significant), this hasn't happened before.

Here's the sequence to the trouble point:

Fraps screen capture at 15fps and the slowest capture rate (0.001) -- size 28 GB

Speed increase to 120fps -- size 28 GB again

Decimate by 4 to get the video back down to 30fps -- 7 GB

Crop only as described above -- still 30fps but 50 GB file size!?

I always change to YV12 somewhere along the way to reduce the size.

I've had many excellent results with Fraps capture on 1920x1200 monitor and similar VD filter sequences before, ending with WMV9 compression (Can't figure out how to use x264 -- might you possibly direct me to a good x264 tutorial?)

I hope all this rambling makes sense!

Thanks for your quick reply,
papilio

[Guest]

Fraps is compressed. If you do cropping and then don't select an output compression you'll get uncompressed. I don't see the problem.

Also, you contradict yourself. One place you say you use uncompressed throughout, in another place you say you use Fraps compression.

I ask again, what are your input and output codecs?

[papilio]

Yes, I realize Fraps is compressed, but from the first frame-rate change on I use VD default (Uncompressed RGB/YCbCr) -- first on the VD compression list -- which of course means from the first run on the file remains uncompressed (except for color format) until the very end (again, both the 5GB output and the 50GB output exit the process uncompressed.)

I realize that this results in huge output sizes, but if I understand correctly (I'm certainly still a relative newbie at this, so I apologize if I'm trying your patience!), VD decompresses the input (except for color format) each time it runs a filter process. Am I mistaken here? There may well be a better way to do it, but I'm comfortable with the gigantic sizes -- though things *do* take a long time uncompressed -- reducing the file size greatly with the final compression. I *hope* this clears up the contradiction you mentioned.

But trying (at last) to answer your question directly, I keep the file uncompressed (Uncompressed RGB/YCbCr) from the first filter pass, change in frame rate (except for the change to YV12 along the way -- perhaps on the third step or so, usually just after adjusting color saturation and sharpening), until the final WMV9 compression.

So my main puzzle is, why the enormous change from something as simple as cropping without changing (or using) the compression for either or anything else drastic, near as I can tell. (Uncompressed RGB/YCbCr). I really don't recall this happening before, but I suppose it is possible (though it's a bit difficult to imagine) that I missed it.

It seems there's something which you need to know which I'm failing to pick up, or to answer. (Again, I apologize, though I am trying! And I did try the search first.)

Thanks again,
papilio

[Guest]

I asked for the codecs used for input and output of your cropping step twice already and you've still failed to answer.

And I don't know what you mean by the "first filter pass".

Cropping cannot increase the size. The only explanation is that your input and output have different compressions.

[papilio]

Hi neoron2,

As I had tried to explain, both the 5 GB file and the 50 GB file went in and out having selected (Uncompressed RGB/YCbCr), which I assume (could easily be wrong) means no codec on either file going in or out, *if* my understanding is correct.

However, I just tried applying msu lossless to both, and they did indeed come out identical! I'm not sure I understand it (well, I know I don't!), But thank you!!

And thanks especially for putting up with the exasperation and patience required in solving my problem!

All my best,
papilio

[qyot27]

The option for Uncompressed RGB/YCbCr doesn't mean it performs no conversion of the video format - it means that the frames in the image are stored without any specialized compression algorithm, and the output size for each frame is calculable using (dimensions x bit depth / 8) / 1000 for the kilobyte value per frame. Now, multiply that value by whatever your framerate is and then multiply again by how many seconds long it is and that's the output size, or thereabouts given container overhead, in Uncompressed RGB - I don't know how to calculate it for YCbCr, as I've never saved files to Uncompressed data in that colorspace.

For no additional compression to be applied in VirtualDub, it is necessary to use Direct Stream Copy mode, in which circumstance no filters are able to be used unless the video is being served in with an AviSynth script (and in that case, it appears to VDub as being Uncompressed anyway - in the circumstances of using a script, the filtering is done in the script, not VDub). Having VirtualDub set on Full Processing mode will decompress and recompress your video while doing a colorspace conversion to RGB and the output size is totally dependent on what you have Compression set on.

[papilio]

Thanks qyot27,

Helpful things to know -- I am learning!

All the best,
Michael