[FFmpeg-user] set image width only?

Tim Nicholson tim.nicholson at bbc.co.uk
Fri Sep 9 08:20:26 CEST 2011

On 09/09/11 03:35, lovelove wrote:
> lovelove wrote:
>> I don't really understand the difference between
>> *-s 400x300*
>> and
>> *-vf "scale=400:300"*
> Aside from the difference from the -s parameter being unclear,
> the -vf scale parameter you suggested to me somehow interferes with key
> frame detection.
> This extracts all key frames of a video as single images:
> *ffmpeg.exe -i inputfile.avi -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync
> 0 -f image2 outputfile.AVI-%03d.tif**
> But when adding -vf scale, *ALL* images are extracted, not just keyframes:
> *ffmpeg.exe -i inputfile.avi -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync
> 0 -vf "scale=400:-1" -f image2 outputfile.AVI-%03d.tif**
> What's going wrong? thank you.

At a guess, because you haven't ordered the filters the resize is 
happening first and therefore all frames become keyframes...

You need to take the ouptut of the select and feed it into the scale...


ffmpeg.exe -i inputfile.avi -vsync 0 -vf 
"select=eq(pict_type\,PICT_TYPE_I) [select]; [select] scale=400:-1 
[out]" -f image2 outputfile.AVI-%03d.tif


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