Video Source Type setting in TMPG

[Bizuser]

I read the online help for TMPGEnc, and it says that it will set the Video Source Type (settings/advanced tab) according to the actual nature of the input video, once you enter a source of video on the main page. Possible values are interlace and non-interlace.

I use Avisynth as my video source for TMPG. I also am doing frame rate conversion, so am using 'assumefps', 'convertfps', etc, in my avisynth script. I noticed the following 'strange' behavior depending on how I set the specific frame rate value, which seems odd. I did the following tests. The avs file fps values may not make 'perfect sense' alone, but I was trying to come up with the most basic script file to test with. My raw material (the input to avisynth) is interlaced PAL 25 fps.

The basic AVS file was as follows:
LoadPlugin("F:\DVD2SVCD\MPEG2DEC\mpeg2dec.dll")
mpeg2source("F:\DVD2SVCD\MOVIE\DVD2AVI.D2V")
assumefps(23.976)

I then changed the fps value and reloaded it into TPMG, and observed the setting of 'video source type' (using 'code' tag to get monospaced text; is there a better way?!)

------------------------------------------------------
assumefps value    video source type
---------------    -----------------
25 (native to src) Interlace
23.976             non-interlace
29.976             Interlace
50                 non-interlace
47.952             non-interlace
59.952             non-interlace
-------------------------------------------------------

Similarly, if I REMOVE the assumefps() line, and insert bicubicresize(480,480,0.0,0.6), the source type remains interlace, while if I change it to bicubicresize(352,288...), the source type becomes non-interlace...

Anyone know why it's doing this (esp. with the framerate stuff; I can imagine why the resize is doing it), and, what's the impact of overriding what it detects? The weirdest thing is that 23.976 is considered non-interlaced, while 29.976 is considered interlaced!

<later...>
I tested with other settings in avisynth; got some good, some strange, results:

---------------------------------------------------------------
Avisynth entry     video source type
---------------    -----------------
None (native)      Interlace
Bob                non-interlace (expected)
bob+weave          Interlace (expected)
separatefields     non-interlace (expected)
smartdeinterlace   interlace (NOT expected!!!)
----------------------------------------------------------------

I've searched the forum but can't find anything on this. Thanks!

[DJRumpy]

The reason is because TMPGenc is guessing. When you used the AssumeFPS(23.976), TMPGenc assumes your working with FILM source material, which is Progressive (Non-interlaced). When you used the AssumeFPS(29.97), TMPGenc assumes your working with either interlaced, or telecined material, so it set the input source setting accordingling.

When you doubled the frame rate, TMPGenc assumes you have deinterlaced your material, by created 1 frame for each field. This is the case with your 50,47.952, and 59.952 fps settings.

When you put in a bicubicresize, with the vertical set to 288 (240), you are effectively de-interlacing a source as well, so TMPGenc changes it's settings accordingling. This is because the drop in vertical size, to 1/2 height, effectvely removes one field, and gives you a non-interlaced output.

TMPGenc is a good piece of software, but it's not going to think for you. It makes an educated guess. It's up to you to make sure it's right. If your input source is telecined, then set it as such, unless you've converted it to progressive with AVISynth in the process.