29 fps -> 25 fps (convert or change)

[delacroixp]

I'm encoding a 7-DVD lecture on 'Creation Science Evangelism' onto 1 DVD... Q23 works fine but I'm pushing for Q22...
It's a 29.97 fps 640x480 resolution release... I should imagine that 25 fps would be more than enough.

AutoMKV has the option for ConvertFPS and ChangeFPS... what's the difference and which would work better...


:):D:eek:
Pascal

[Guest]

Read the Avisynth documentation for an explanation of the filters. 'Better' is subjective here.

[delacroixp]

Read the Avisynth documentation for an explanation of the filters. 'Better' is subjective here.
Quite right... 'better' is so ambiguous and I'm pretty keen to see the results regardless... eventhough a drop in filesize without a percieved drop in motion-quality would be welcome...
I should also have made more effort to find a manual and do a little research... but your input is still appreciated...

@delacroixp

from avisynth manual

ChangeFPS changes the frame rate by deleting or duplicating frames.

The AssumeFPS filter changes the frame rate without changing the frame count (causing the video to play faster or slower). It only sets the framerate-parameter

ConvertFPS: the filter attempts to convert the frame rate of clip to new_rate without dropping or inserting frames, providing a smooth conversion with results similar to those of standalone converter boxes. The output will have (almost) the same duration as clip, but the number of frames will change proportional to the ratio of target and source frame rates.

also.. pay attention to audio.. maybe you must use the advanced audio fuction, expecially the Tempo.
your formula for 29.97 to 25 should be this (100.0*30.0*1001.0)/25000.0

It seams like ChangeFPS is the way to go...


:thanks: much...


:):D:eek:
Pascal

[Awatef]

Wow wow wow, hold it there, it's not about "25 fps would be more than enough", it's about wether you want PAL output or not.

If it's just about "saving bitrate", I shall stop you right there. I would rather "sacrifice" resolution, than corrupting the video. You can go down from 640x480 to 576x432 and get the same bitrate savings. I challenge you if you could tell the difference in fullscreen.

If it's about getting PAL output, I would recommend converting to 25i like this:

ConvertToYUY2()
ConvertFPS(50)
SeparateFields()
SelectEvery(4,0,3)
Weave()

Using ConvertFPS instead of ChangeFPS will blend frames together instead of deleting or duplicating frames, making the motion much smoother.

[Blue_MiSfit]

I second Awatef's post.

You never want to change the frame rate unless you have a VERY good reason to do so - i.e. streaming, or for a format conversion.

If you want to save bitrate (improve compressibility) then decrease resolution, or add some denoise filters.

~MiSfit

[delacroixp]

I have to confess that it was pure and simple selfishness on my part... trying to get more for less...

As it turns out... the file is 15% smaller, though I can't play it since none of the regular players (Zoom, VLC, MPC) can find the 'SegmentInfo'...
Perhaps, it looks alright... in which case I should actually do a 'consistent' 15 ChangeFPS... rather than having 80% of 30 fps and 20% of 15 fps...
NTSC and PAL are both great codecs, NTSC favouring faster action (more fps) while PAL favours clarity and detail (more res).

Ideally, we could encode from source material and encode at 30 fps when necessary... or 20 fps or less when circumstances do allow (eg Sleep (http://en.wikipedia.org/wiki/Sleep_%28film%29) and Empire (http://en.wikipedia.org/wiki/Empire_%281964_film%29), which was actually shown at 16 fps). Some movies look equally good at 1280x720 and 640x360 (eg, white scenes of polar-bears making love in the snow... lol).

The idea that 'x' fps or 'y' resolution is best for all movies... is falacious at best... akin to encoding all movies at the same bitrate...


:):D:eek:
Pascal


/******************************* EDIT **********************************************
/* Perhaps I should simply do a 2-pass with a blanket 10% reduction in filesize from the 21-CQ-CRF encode...
/* I've never tried 2-pass and a 22-CQ-CRF gives a 20% decrease in filesize..
/* Ran out of disk space (see post (http://forum.doom9.org/showthread.php?p=1007957#post1007957)).
/* 576x432 is looking increasing attractive
/*********************************************************************************

[delacroixp]

I encoded the series @ 544x432 and Q20 (serious L & R cropping)...
I even included an XML menu with an option to install the CCCP (http://www.cccp-project.net/) codec and player pack... with 4 MB to spare... now that's maximising space.

The colours are stunning and also more saturated than Q22 or even Q21...
I just hate downsizing... it feels like I'm 'corrupting' or 'destroying' the poor guys video... but the overall results are pretty awesome...


:):D:eek:
Pascal


/*********************** NOTE *******************
/* The DVD series is copyright © 2007 and
/* 'Permission is granted to duplicate for free distribution only.'
/***********************************************