Overscanning issue when encoding

[SolarLamp]

Is it possible to be rid of the overscan problem when encoding? any helpful suggestions would be appreciated, thanks in advance

[adam]

Well you cannot get rid of overscanning but you can encode around it. It doesnt actually change what you see but it saves you some bitrate so the overall quality should be better.

Most tv's crop out around 12-16 pixels from all sides. All you need to do is crop this portion of your picture and add black bars to fill the gap. There's no point in wasting bits on the part of your picture that you don't see.

The easiest way to do this would be with FitCD. It can take overscanning into account and create an AVS script for you to frameserve with. If you are just using TMPGenc then you can simply add a black mask over these pixels. Look in advanced/clip frame. If your movie is widescreen then you need only do this on the sides, if its fullscreen do it on top and bottom as well.

Again, it won't look any different on the television. But the black bars will be cut off instead of picture, so you ended up with less to encode. If you plan on watching any of your vcds/svcds on your pc than you may not want to do this since the black bars will be visible, as overscanning doesn't occur on pc monitors.

[klaymen]

Thanks for the FitCD tip, this was new to me as well :-)

Another interesting feature in TMPGEnc is the "Video arrange" setting, which allows you to add (instead of overlay) black borders. If you have a source with a given vertical resolution, it's a good idea to avoid vertical resampling.

Let's assume you got a DivX of a widescreen edition, usually in a 640x272 pixel resolution, and you'd like to convert it to MPG2, DVD-resolution (720x480). You COULD try to make an anamorphic version of it, but it would be futile as your original vertical resolution is only 272, which is exactly the vertically used widescreen resolution in a letterboxed 4:3 version (NTSC 4:3 is 640x480, and 480/(2.35/1.33) = 272). So you'd like to make a 4:3 (letterboxed) version with vertical 272 resolution and add black borders. You can do that easily using TMPGEnc in "Advanced" tab. Under "Video arrange method", choose "Center (custom size)" instead of "Full size" and enter "720x272" as reolution just below. This will re-sample your original 640x272 source to 720x272 (so only a horizontal resampling) and add black borders on top and bottom to the output resolution, which should be 720x480 (this resolution must be entered in the leftmost tab of TMPGEnc as output resolution, default for NTSV DVD).

Another example: Using my analog DC10+ capture card, I can capture MJPEG video in a TV-crop mode, which already cuts away the overscan border from beginning (it actually cuts it away, it is NOT an overlay operation, so pixel density of 600x450 is the same as in full 640x480 mode). Of course it is unwise to convert this directly to an MPG2, because this would "zoom in" the captured video to full size, adding overscan area again. So some formerly visible parts drop out into the overscan area, plus you loose sharpness because of re-sampling. The calculation is like this: The DC10+ would normally capture in a 640x480 reolution. In TV-crop mode, it only captures 600x450 pixels (which roughly corresponds to the TV-visible mode - it also removes the ugly bottom scanlines that appear if you capture from analog video tapes). To compress this in TMPGEnc, you would use again "Center (custom size)", but enter 675x450 as resolution in Advance tab (because horizontal DVD-resolution is 720, and 640:720 = 600:675). This re-samples your source only horizontally (600x450 to 675x450) and adds black borders on all 4 sides to blow it up to 720x480 (full DVD-resolution). Particularely considering interlacing it is useful to avoid vertical resampling.

SVCD, of course, needs other values (I guess 450 horizontally instead of 675, so it's 450x450 in the second example).

Unfortunately I know no way to use similar conversions in programs like CCE. As CCE doesn't seem to be able to deal with frameservers (at least not last time I tried), I'm still sticking with TMPGEnc.

Regards from the Neverhood :-)

Klaymen

[adam]

CCE works perfectly fine with frameservers. Just use avisynth, this will give you many more options than just TMPGEnc alone.

[klaymen]

Yes, but it only works with Cinemacraft 2.50... 2.62 or 2.64 don't take Avisynth files. There's a tool I read about (link2) that should make it possible, but I don't have it.

Also, after I used CCE to compress a 23.97fps XVid source, followed by pulldown (0.99) to convert it to 29.97fps, Scenarist rejected the resulting .mpv file. It complained about more-than-36-pictures in a GOP (#2) or between sequence headers. SpruceUp and Maestro would accept it, but not Scenarist (and only Scenarist supports AC3 sound...). I hope TMPGEnc is working (worked until now). Hmm.. guess I'm a bit OOT now :-)

Klaymen

[adam]

http://www.doom9.org/Soft21/SupportUtils/Link2v095.zip

There is a link to link2, you can use avisynth with any version of CCE now, though using link2 won't be as fast when using a dvd source.

Also the very latest builds of CCE 2.64 also support avisynth directly, in addition to 2.5.