How to scale during transcoding?

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paul1n
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How to scale during transcoding?

Postby paul1n » 21 Jun 2007 14:40

I'm experimenting with VLC to transcode TV captures to mpeg2.
In order to avoid deinterlacing artefacts I drop odd fields. The resulting video size is 720x388 (PAL with only half the frame height).

What I want is to scale up by 2x in the vertical direction to end up with 720x576 pixels.

In VirtualDub this is very easy, using the resize filter. But Vdub can't generate mpeg2.

Struggling with VLC now to do the scaling. Tried transcode{width=720,height=576...} but somehow a weird aspect ratio gets written into the mpeg file, so that the image is stretched to 1440 pixels horizontally. Tried to fix the aspect ratio by using --sout-transcode-canvas-aspect but this just adds black padding, leaving the image as stretched as before. Other aspect ratio options seem only to work with display output.

Anyone an idea how to perform the resizing?

PS I know the AR can be fixed during playback in VLC but I want to burn the mpeg to DVD and play it on my home player. My player does not support Mpeg4 so I have to use Mpeg2. A 2-step solution works (VirtualDub => Divx with scaling, then VLC => Mpeg2) but I'd rather avoid the quality loss.

Paul

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