Keep MPEG2 Interlace+Telecine in AVI

[ScottZ]

Sounds odd I know, but I'm converting mpeg2 source material for use with a video editing card and need to keep things as they are. The source material is 24fps and encoded for 29.97fps.

The card has it's own AVI Codec and requires to have files encoded with it in order use them in realtime with the hardware. Unfortunatly, the codec has no options to set, so it is very limited in scope.

The majority of the tools I've tried will always default to converting an MPEG2 interlaced+telecine source to progressive+IVTC (which is understandable), but have problems getting them to not do both conversions.

In some cases I've been able to turn off the IVTC conversion, but the resulting frame is still being output as a progressive image to the codec.

I've tried going the Interlaced+Telecine 29.97 -> Progressive+IVTC 24fps -> 29.97 Interlaced+Telecine route with marginal results.

Any recommendations on what tools to use for converting MPEG2 -> AVI and keep the interlace+telecine?

Many Thanks,
-Scott

[Tommyknocker]

Have you tried loading the MPEG-2 file into Virtual Dub mod and saving under a different codec?

[FOO]

Avisynth can do anything you can think of almost.

[ScottZ]

Thanks for the tips, but still no go on VirtualDub Mod (unless I'm not seeing the options correctly).

VirtualDub Mod senses that the Mpeg is at 24fps (23.97) and wants to go progressive. Under Frame Rate there isn't an option to keep Interlace. The None option under Inverse Telecine is Progressive output. Changing frame rate just stretches out the timing on the progressive frames it generates.

TMPEG and Flask see that it is at 24fps, but know it is telecined at 29.97 and can read the fields, but again, just generate progressive frames.

The problem doesn't seem to be reading the frame in it's interlaced+telecine format, but in sending the frame by field to the codec.

I know the codec can handle it as that is how it captures analog NTSC video.

I'm having trouble with AVISynth, but still working on it.
Any help would be appreciated in reading the mpeg2 file and serving the interlaced frames correctly.

Thanks again,
-Scott

[Tommyknocker]

Since you are working on AviSynth, my current favorite AviSynth GUI is AVSGen. I run it, choose the MPEG I want to open and it generates the script and will run the script if you like.

[ScottZ]

Ok.. I spent the day trying this out.

I can split the fields, but it is still being sent out in a progress frame format. So far I don't see how to use AVI Synth to solve what I'm after.

I need to send to the codec the odd field first (without completing a frame). Then the even field to the codec (and now complete the frame)

All the tools I've tried that have interlace/field options wind up sending a complete progressive frame. It is reading the interlaced fields but is sending a sequential line frame.

They create a frame buffer, fill it in with the interlaced lines, and then send lines 1,2,3,4.. (etc) sequentialy to the codec. This creates a "psuedo interlace" frame.

I need to truely send lines 1,3,5,7 followed by lines 2,4,6,8 to the codec.
This is how the captured files are stored.

The best I can get AVI Synth to do is create seperate frames with seperate fields.

Any ideas?

[FOO]

Now that I think about MPEG->AVI interlaced,
I have decided it's impossible .
AVI has no provision for interlacing.

[ScottZ]

Not true.

[FOO]

Possibly so , I guess I have to go look it up.
so how do you produce an interlaced uncompressed AVI ?
That is the desired Avisynth output.
I know Avisynth keeps track internally
and SeparateFields() should produce field based video.
adding AssumeFieldBased might help

Come on Scott , tell us how it works

[ScottZ]

DirectShow encoded AVI video streams can support interlaced video if your codec can (which mine can).

OpenDML (AVI2) formated headers support Interlaced Video data

DV Video AVI (AVI1 and AVI2) support interlaced video

To simply say there is no support isn't true.

And this isn't something new, even my old Miro/Pinnicle DC30 stored video in MJPEG interlaced format.

You can simply tell by seeing the field artifacts on a single frame when stepping through a video and watching it on a NTSC montior.

HOW to do it with the tools available is the quesiton.
If I knew how, then I wouldn't be asking.

[FOO]

Yes , I have brain damage, I did a lot of DV and had to worry about
field order. Can't remember stuff for more than a week.
My MJPEG codec has a check box for "2 fields if more than 240 lines"
That may mean the output is field based .
So what's an easy test for whether an AVI is interlaced or not ?

Avi codec doesn't seem to know
Gspot says TYPE: OpenDML I/L: Not supported on one of
my Mjpeg AVIs

[FOO]

You can simply tell by seeing the field artifacts on a single frame when stepping through a video and watching it on a NTSC montior.

I don't know about that. How do you tell the difference between
loading a frame and
loading two fields ?