a bit confused with frame sizes

[flanagann]

I'm capturing from TV with a 768x576 frame size (I've been told it's PAL native resolution). Then I'm using RealProducer to encode the file to .rm.

I don't know if it's OK to capture in 768x576, since the video files will finally be used in a Web, and not in a TV. Should I capture in other resolution such as 640x480, in order to save some size??

Could anyone one explain this concepts??

Thanks and regards!

[jggimi]

In brief: 768x576 will capture the most detail. Analog video doesn't have resolution, it has lines. Our capture devices convert these to pixels, and that's as large as you can get.

But 768x576 does not use square pixels, and that is what Real video uses, since its designed for output on PCs, which have square pixels.

Best practice is to capture at maximum resolution (assuming you have the disk space) and then to resize as needed for your final output.

For more information, please refer to our handy Capture Guide (http://www.doom9.org/capture/start.html), which has two whole chapters on frame size selection.

[WildCelt]

To add to jggimi's excellent advice, I would definitely resize to something even smaller than 640x480 if you intend it to be encoded to rm and used on the web.

[Boulder]

The optimal capture resolution depends on the chipset the capture card has. Capturing at 768x576 might mean that the card is sampling at a lower resolution and then stretching to the desired resolution which is not preferable. The capture guide contains some information which should be useful in this case.

[Inc]

But 768x576 does not use square pixels, and that is what Real video uses, since its designed for output on PCs

768x576 digitally equals to PAL square pixels at PAR1:1 (768/576 = 4/3) so the size is perfect for shown on a PC. But as Boulder said, the case depends on the Capturedevice and its capturewindow-result.

With real 4:3 captures he can directly resize to any 4:3 PC final resolution like 640x480 or 384x288 ... deinterlacing or YXZbobbing in case of interlaced captures would be obligatory for pc/web display purposes.

[jggimi]

768x576 digitally equals to PAL square pixels at PAR1:1You're right! I was thinking "720x576." Sorry for the misinformation.