[libav-bugs] [Bug 517] add framestep video filter

bugzilla at libav.org bugzilla at libav.org
Tue May 26 00:56:51 CEST 2015


--- Comment #5 from Nikoli <nikoli at gmx.us> ---
Created attachment 537
  --> https://bugzilla.libav.org/attachment.cgi?id=537&action=edit

> Framestep sounds like a simplified https://www.libav.org/avconv.html#select and probably can be implemented on top of it.

Thanks! Indeed "select" video filter works fine, migrated to
--vf=lavfi=[select="not(mod(n\,${every}))"] mpv option.

Adding "framestep" alias to select="not(mod(n\,${n}))" seems useful.

> why it is important to have mpv use this filter?

avconv does not support DVDs and BDs, with mpv it is possible to extract frames
from them without remuxing. Other reasons for using mpv are mostly historical:
mplayer, mplayer2 were my main video players and now mpv is. I better know how
it behaves, how to use it and what expect.

But mpv seems to miss several important features: it is not able to save frame
number and type.

Anyway it would be nice to have avconv based version of attached script, so
help is appreciated.

> Please elaborate how you intend to use it.

1) Encode some video with different encoders and/or settings.
2) Extract same frames from various parts of source and video encodes.
3) Open these frames in image viewer and look how different encoders and
encoding settings affect picture details and quality.
4) Decide what encoder and settings use for final encode.
5) (Optional) Upload frames from source and encode for comparison.

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