Reduce Quilting artifacts - SVHS to DV

[Topsy]

Hello there,

I'm getting really bad quilting when passing through VHS through DV into PC.

Are all DV codecs the same or does anybody have any suggestions for an alternative PC DV codec and/or way of reducing the effect? Alternatively, anyone using a good relatively in-expensive non-dv capture card ?

many thanks in advance,

t

[johnmeyer]

It would be helpful to get at least a screen shot; a short clip would be even better.

"Quilting artifacts" is not a term I'd heard before, but it sounds like it might possibly be dot crawl. If it is dot crawl, then it is probably not caused by the DV codec, but instead might be from the way analog video is encoded. I am less familiar with PAL video than with NTSC, but I think PAL has a similar issue where the chroma and luma interact in such a way as to create "cross-hatch" patterns (the more typical term to describe this problem). The solution, if that is your problem, is to make sure you use an S-Video (rather than the yellow composite cable) connection between the VHS deck and the DV capture card (or camcorder, if you are using the pass-through on a DV camcorder). This should completely eliminate the problem.

BTW, a way to tell if it is dot crawl is that you will find that the problem is worse where this is lots of color, as in this image:

[JVRaines]

According to Adam Wilt:

Quilting shows up as discontinuities between adjacent DCT blocks in an image. They are most noticeable in DV on straight diagonal lines that are slightly tilted from the horizontal or vertical. Quilting is also common to other DCT compressors like those used in JPEG and MPEG.

Quilting is most often seen on DV footage as a "fixed pattern" distortion during slow pans or tilts. It can be accentuated by maximizing the "sharpness" or "aperture" control on a high-resolution video monitor (such as the 600-line Sony PVM series), which really brings it out, often to a frightening degree.

The 72-pixel by 48-pixel detail of the larger scene shows quilting on the edge of the table. The small arrows at the bottom of the image are aligned with the DCT block boundaries, every 8 pixels across the image.

[johnmeyer]

Excellent example, although I don't see anything different from the normal, inevitable staircasing that happens when diagonal lines are digitized by a finite number of pixels, and also the blocks that get created by any scheme that compresses using an algorithm which groups pixels into blocks.

I am in no way trying to be argumentative, but am only saying that this doesn't seem like anything different than what I'd see in almost any blow up of digital video from pretty much any source, using almost any compression scheme.

[SameSelf]

Hello there,

I'm getting really bad quilting when passing through VHS through DV into PC.

Are all DV codecs the same or does anybody have any suggestions for an alternative PC DV codec and/or way of reducing the effect? Alternatively, anyone using a good relatively in-expensive non-dv capture card ?

many thanks in advance,

t

I don't use it so much versus I just happen to have it (cuz it was so cheap) and have tested it (so I know it works well), but the I-o Data GV-USB2 capture device can be had for only ~$40 USD and captures to uncompressed YUV422 video versus DV-AVI. There are of course other similarly priced USB capture devices that capture to lossless formats on the market today. Not saying the GV-USB2 is the best or if capturing to YUV422 will even solve your problem, just offering up a suggestion to your question.

[Topsy]

Here is a still of the quilting through DV (left) and the same image captured years ago when I had access to ProRes/Blackmagic kit:



Source is VHS. You can see the "block boundaries" on the stripes of the shirt are present on DV.

The frustrating thing is that now I've noticed them I see them on everything I've captured! Noisy footage tends to exaggerate them more it seems.

[vhelp]

The frustrating thing is that now I've noticed them I see them on everything I've captured! Noisy footage tends to exaggerate them more it seems.
Image Attached Thumbnails

This was always a problem with interlace video, and the more you move or faster you panned the camera the worse the temporal-dis-joining of lines become, such as the example in your jpeg photo. The faster you moved/panned the camera on certain objects/scenes, the greater the distance of those objects or portions of a given scene will be between fields, the fields make up a frame. And de-interlacing them will show poorly in scenes like these. But I have noticed in some home cameras that they were slightly better at this. I have an old camera (still do) that does very similar to yours. If the camera were completely still, (not steady in your hand) those lines would be much clearer and uniform. Plus you exaggerated the proof slightly by saving it as a jpeg, and not to mention it is from vhs. I would recommend that you encode this with the highest bitrate you can afford w/out going past the standard, assuming dvd, if you want to reduce the visual noticeable-ness of these artifacts during playback.