[FFmpeg-user] Save webcam stream in mpg, not avi format

[Roger Pack]

On 8/28/15, Felix Baier <felixbaier-at-yahoo.de at ffmpeg.org> wrote:
> Hi Eugen —
>
> I have done some more testing of the code and run the camera for a night. I
> should get 8-9 videos of each one hour length per night. However, I get 4
> videos of one hour length, but at twice the speed. The frame rate apparently
> is unaffected by this (still 25fps), at least as far as it is displayed in
> the properties of the videos.
>
> I changed “-vcodec mpeg4 -qscale 2” to “-vcodec mpeg4 -q:v 2” after I got a
> notification that the first version was ambiguous. The complete code I used:
>
> ffmpeg -r 25 -f dshow -s 640x480 -i video="Microsoft LifeCam HD-5000”
> -vcodec mpeg4 -q:v 2 -f segment -segment_time 3600 -reset_timestamps 1
> -segment_start_number 1 -segment_format avi -r 25
> c:\Users\Desktop\out%%03d.avi
>
> Any idea what might be going on?

I believe your problem here is the use of "-r" for the input, which
basically means "override what its actual framerate is, and pretend
that its 25 fps"
https://trac.ffmpeg.org/wiki/DirectShow#Specifyinginputframerate
(any ideas out there for how we could make this more clear? Is this a
general aspect more than just dshow?)
Cheers!
0roger-