aliasing when capturing analog Component v.s S-video

[clashradio]

I've been testing/capturing my NTSC laserdiscs with VirtualDub, using s-video from either the player or my external comb filter device(s) with great results. Decided to capture via Component from the various comb filters and I'm getting lots of aliasing. I've tried capturing RGB24 and other settings, same results.

VirtualDub settings: [VIDEO] uncompressed 4:2:2 YCbCr (YUY2) {I currently can't capture lossless} [AUDIO] PCM 16/48

Attached are two captured stills from the Snell & Wilcox test pattern. You will notice aliasing in the Component-test in a few areas, but most noticeable around the large, black circle.

Same capture settings for both. Any ideas?

[jagabo]

The fields are stored in the wrong location. The top field is stored as the bottom field, the bottom field as the top field. Ie, instead of the scanlines being stored in order 0,1,2,3,4,5... pairs are swapped 1,0,3,2,5,4...

You can fix that with SwapFields() in AviSynth, or the Field Swap filter in VirtualDub. You may be able to fix it while capturing in VirtualDub by enabling video filtering and adding the Field Swap filter.

[clashradio]

Thanks jagabo.

Adding SwapFields() to the AVISynth code worked, and enabling Swap Fields in VirtualDub while capturing also worked.

[jagabo]

By the way, colors looked a little sharper in the component capture.

[pandy]

By the way, colors looked a little sharper in the component capture.

Rather composite not component - seem S-Video doesn't work.

[lordsmurf]

Lots of external comb filter devices screw with video in a negative way.
You see that in DVD recorders, etc.

[clashradio]

Lots of external comb filter devices screw with video in a negative way.
You see that in DVD recorders, etc.

This particular test was with a Toshiba dvd recorder as a pass-through for it's 3D comb filter, using Component output. The other external comb filters I've tested only have s-video out. I was hoping to take advantage of Component for it's brightness and color separation.

But then I got to thinking; Component is sometimes labeled as Progressive output on consumer devices, as in line-doubler. Could this be why I had to swap fields during capture? I think some comb filters work as Frame and some work as Line?

[jagabo]

But then I got to thinking; Component is sometimes labeled as Progressive output on consumer devices, as in line-doubler. Could this be why I had to swap fields during capture? I think some comb filters work as Frame and some work as Line?

Most capture devices won't capture anything from a line doubled signal. The few times I've see samples of progressive output being captured by a device expecting interlaced NTSC video you see two half width pictures side by side. This is because the progressive signal is twice as fast as an interlaced signal.

[clashradio]

At one point I had a video processor which outputted @480p via HDMI, which my capture device recognized as NTSC Progressive. I sold it due to all research pointed towards capturing at 480i 29.97.