user23253: I want to crop a video frame sequence by frame number. For example for 10000 frames  sequence, i want to crop it 750 frame from beginning.

user1871: FFmpeg's image sequence demuxer has a start_number option, so if you want to skip img_0749.jpg and start from img_0750.jpg, you would start your command as follows,
ffmpeg -start_number 750 -i img_%04d.jpg ...

See the docs for the image2 demuxer at http://ffmpeg.org/ffmpeg-formats.html#image2-1

23253: <p>I want to crop a video frame sequence by frame number. For example for 10000 frames  sequence, i want to crop it 750 frame from beginning.</p>
 1871: <p>FFmpeg's image sequence demuxer has a start_number option, so if you want to skip img_0749.jpg and start from img_0750.jpg, you would start your command as follows,</p>

<pre><code>ffmpeg -start_number 750 -i img_%04d.jpg ...
</code></pre>

<p>See the docs for the image2 demuxer at <a href="http://ffmpeg.org/ffmpeg-formats.html#image2-1" rel="nofollow noreferrer">http://ffmpeg.org/ffmpeg-formats.html#image2-1</a></p>
