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How HDFVR and webcams handle unsupported resolutions


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#1 Octavian

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Posted 23 April 2013 - 04:05 PM

When you configure HDFVR to use a certain resolution and framerate , the final recording is not 100% guaranteed to have the same resolution ( and framerate).

The reason is because not all webcams support all resolutions. Newer webcams like the leading Logitech c920 support a miriad of resolutions but older ones only support the basic 16:9 and 4:3 ones OR do support bigger resolutions (like 1280x720 or 640x480 ) only at 15fps. Some ancient ones might not even support anything other than 320x240 @ 10 fps.

So what happens when HDFVR is configured to record 1280x720@30 fps and it's run from a computer with an old webcam?

This is what happens:
  • The webcam returns a video stream with the closest resolution (to the resolution and fps configured in HDFVR) and fps it can
  • HDFVR shows the webcam using the ratio of the resolution of the stream coming from the webcam (not the resolution configured in HDFVR)
  • HDFVR scales the image up or down (keeping the new ratio) to fill the black video area in HDFVR as much as possible. Keeping the ratio means balck borders will be present.
  • the final video file has the same resolution as the one returned by the webcam
An example:

I have configured HDFVR to use a 714x113@30 fps. A really wierd resolution.
Then I run that HDFVR on a 4 year old LG notebook with an integrated webcam.
The webcam returned a really dodgy 708x112 video (I had asked for 714x113). The final .flv file had the same resolution (708x112).
All the time HDFRV showed the 708x112 video whille keeping the aspect ratio at 708:112 (and not 714:113).




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