29.97 to 23.976 - Audio change?

[TheLastOfThem]

Hi everyone,

I changed a 29.97 source to 23.976 and then Decimated. The source is now longer than the same 29.97 source. Do I need to slow down audio to compensate? I remember reading how 23.976 audio is the same as 29.97 audio? But found that confusing as to how that's possible

[manono]

I changed a 29.97 source to 23.976 and then Decimated.

What? How did you change it? With an AssumeFPS? If so, bad move. When one talks about changing from 29.97fps to 23.976fps, they usually mean performing an IVTC.

If that's what you're trying to do for a DVD source you first make the D2V project file using 'Honor Pulldown Flags' as the Field Operation, followed by opening the video using MPEG2Source and then do the IVTC using something such as:

TFM().TDecimate()

The framerate changes from 29.97fps to 23.976fps, the length remains the same and the audio remains in synch. If your audio went out of synch you did something different.

As usual, if you're asking for help on what to do with a DVD source you have, cut a small piece using DGIndex and upload it here.

But found that confusing as to how that's possible

As the result of an IVTC the framecount is cut by 20%, the framerate is cut by 20%, and the length remains the same.

[jagabo]

It depends on how you did the frame rate conversion. The 23.976 fps video can have the exactly same running time as the 29.97 fps video, or it can run 25 percent longer, depending on how you did the conversion. Or if you totally screwed up it could be something entirely different.

[TheLastOfThem]

It depends on how you did the frame rate conversion. The 23.976 fps video can have the exactly same running time as the 29.97 fps video, or it can run 25 percent longer, depending on how you did the conversion. Or if you totally screwed up it could be something entirely different.

I decimated to 23.976 I did not do ChangeFPS. Source was 29.97 - I used QTGMC (keeping fps the same / no bob) and then TDecimate(mode=0)

[manono]

I changed a 29.97 source to 23.976 and then Decimated.

I used QTGMC (keeping fps the same / no bob) and then TDecimate(mode=0)

Make up your mind. You can't have it both ways.

Post a sample. Or if you're trying to IVTC it, I gave you how to do it above.

[TheLastOfThem]

How does one decide between Resampling the FPS (which just increases/decreases frames while keeping duration fixed - similar to bob deinterlacers) versus DECIMATING to 23.976?

[johns0]

Why did you change the fps in the first place?29.97 is better than 23.976 if both are progressive.

[TheLastOfThem]

Sorry manono! I meant I changed the 29.97 source to 23.976 THROUGH decimation.

Source does not show 3:2 pulldown but a rather odd pattern...1 interlaced frames and 4 uninterlaced frames.

[TheLastOfThem]

Why did you change the fps in the first place?29.97 is better than 23.976 if both are progressive.

I'm not sure....I guess I'm assuming a lot and that the source is a cartoon meant to be seen at 23.976?

[TheLastOfThem]

Source

http://www.mediafire.com/download/4x4s8mzhwhxz7br/sample_%281%29.mkv

[davexnet]

It's a tape capture ? How did it become 59. 9 frames per second ?

[TheLastOfThem]

It's tape. No idea how it became 59.94....

[davexnet]

Is this your capture? What device and software did you use ?

Is the file you provided the actual capture file? Or some conversion ?

[TheLastOfThem]

uPPED RAW file

[TheLastOfThem]

Yeah I believe it's just a mediainfo error....I made the file 14fps and then it reports "Framerate: 29.97"

It still runs at 15fps. Doing 29.97 as the fps reports 60p but it isn't running as that.

[TheLastOfThem]

Here is the raw file...as you all can see it is 29.97. Not sure why it becomes 60p using mkvmerge

http://www.mediafire.com/download/ok563h5heka058k/rawfile.m2ts

[davexnet]

I'm not sure why the frame rate is changed, perhaps somebody who knows more about the file type can explain.

you can access the original m2ts using FFmpegsource in Avisynth, or even directshowsource .
Once you get the proper frame rate you can use tfm().tdecimate()

[TheLastOfThem]

ironically FFMpegSource sees the .m2ts as 59.94 fps in AviSynth

[johns0]

The reason it see's it as 59.95 fps is cause it's interlaced,best to leave it as is rather than butchering it.

[TheLastOfThem]

So it's just a pure interlaced source. I really rather butcher it. Any idea what fps to put it to?

[jagabo]

It's not a pure interlaced source. It was once film. But your capture is so poor the usual ivtc methods don't work right.

LWLibavVideoSource("rawfile.m2ts") 
TFM(cthresh=15) # field match
TDecimate() # restore original 23.976 fps
Vinverse() # reduce residual combing from poor horizontal time base

That mostly works but there are some frames with aliasing artifacts because there are occasional duplicate interlaced frames that didn't field match properly.

[TheLastOfThem]

How can you tell if its film? Most things are film aren't they? At least for cartoon drawn at 8fps and made into film ...

[jagabo]

This appears to work adequately for this clip:

LWLibavVideoSource("rawfile.m2ts") 
TFM(field=0, pp=0)
TFM(field=1, pp=0)
# maybe another TFM() here without pp=0 to deinterlace any orphaned fields
vInverse()
TDecimate()

You need to check this on some smooth panning shots to see if it breaks down. There will probably be some back and forth motion.