[FFmpeg-user] Fw: Re: Confusion about fieldmatch, decimate and framerate

[Nicholas Robbins]

--- On Thu, 11/7/13, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> From: Carl Eugen Hoyos <cehoyos at ag.or.at>
> Subject: Re: [FFmpeg-user] Confusion about fieldmatch, decimate and framerate
> To: ffmpeg-user at ffmpeg.org
> Date: Thursday, November 7, 2013, 10:06 PM
> Nicholas Robbins <nickrobbins
> <at> yahoo.com> writes:
> 
> > > > Uploaded to upload.ffmpeg.org/incoming as
> > > sample-robbins.mkv
> > > 
> > > The sample claims to be 60fps while it actually is
> 30fps.
> > > Assuming you produced the mkv file from a MPEG
> original:
> > > Is the problem also reproducible with the original
> mpeg 
> > > file?
> > 
> > So I get the original file using mplayer's dumpstream.
> 
> Could you provide that sample?
> I am not saying there is much difference, but reporting a 
> problem with the original sample is generally slightly 
> better (I will open a report).

I uploaded a sample vob from a source that appeared to have the same issue.

> 
> Some random additional comments:
> The decimate filter is "stupid", it will produce a cfr 
> output that depends on the fps of the input, the filter 
> can only work for cfr input with correct frame rate.
> You can get this input by using the fps filter first, 
> since your sample is (apparently) really 30fps cfr, the 
> fps filter neither drops nor duplicates frames, it only 
> adjusts the frame rate.
> I originally suggested "fps=30000/1001" and "r 24000/1001" 
> but it appears to me the sample is actually 30fps (and 
> not 29.9), so better values (if the sample is longer than 
> one minute) may be "fps=30" and "r 24".

How could you tell what the actual frame rate is?

> Carl Eugen
> 
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