Cropping video question

[miklg21]

So I don't really understand this whole cropping thing. I have noticed that every video converter has the option to crop a movie. When you crop a 16:9 movie it gets rid of the black horizontal bars right? So if it does that is it stretching the video to fill those areas now?

Thanks

[twolfe18]

i dont really understand the part of your question about stretching, but i will try to explain this as simply as i can. cropping is useful because it ensures that all of the data that you are using to encode the video is going towards improving the quality of the picture you are interested in rather than just black bars. if you have a given video and you encode it two times at the same bitrate, once with the black bars included and once with them cut out: the video with the black bars cut out will look better. the reason for this is that the encoder has to spend energy (in this case energy is cpu time and bits) to describe the black bars, but if you cut out the black bars, the encoder can focus all of its energy on the picture between the bars. stretching has nothing to do with this.

[miklg21]

thanks for the info. So when you crop what does it do with that section ( the black bars)?

[Abond]

Yes, it will stretch the video to fill these areas

[twolfe18]

if you crop the video and set the resize to the same aspect ratio as before the crop, then it will stretch the video to fit the frame, but this should rarely (if ever) happen. when you crop, you should end up with a final aspect ratio that matches the video (without the black bars) rather than the original format (be it 16/9 or 4/3) so that stretching does not occur. if you are stretching (or more specifically, stretching one axis more than the other), then you have not corrected for the aspect ratio properly.