To prepare this context, we use the sws_getContext function, which is going to want our source width and height, our desired width and height, the source format and desired format, along with some other options and flags. It's kind of like a prepared statement in SQL or a compiled regexp in Python. This allows us to compile the conversion we want, and then pass that in later to sws_scale. But first, we're going to have to set up what's called an SwsContext. The basic function we're going to use to scale is sws_scale. Once FFmpeg is installed, you can crop and scale your video by using the following command: FFmpeg -i input.mp4 -crop top 403 -crop bottom 315 -scale 720×405 output.mp4 How to install FFmpeg on Linux When installing FFmpeg on a Linux server, you should have the corresponding package in your repository. In other words, it's the preferred way to do scaling. This new interface is more modular, faster, and I believe has MMX optimization stuff. Whereas before in our player we would use img_convert to go from RGB to YUV12, we now use the new interface. For example you can use mp3 or aac with an mp4 file (container), but not with webm files.Printable version Text version Tutorial 08: Software Scalingįfmpeg has recently added a new interface, libswscale to handle image scaling. ) and for each format there is a set of audio/video codecs accepted.

Notice that there is a set of formats (containers) accepted by browsers (most admit mp4, some also webm. $ ffmpeg -i INPUT -s 320x240 -c:a copy -c:v vp9 OUT.webm Vp9 will provide nearly 50% extra bandwidth saving, but only for supported browsers (Firefox/Chrome), and the encoding will much slower compared to libx264 (that itself is much slower that v:c copy): $ ffmpeg -i INPUT -s 320x240 -threads 4 -c:a copy -c:v libx264 OUT.mp4

The libx264 is recommended if you want compatibility with all browsers. Notice that once you start decoding-filtering-encoding (i.e., no copy) the process will be much slower (x100 time slower or even more). Video copy will ignore the video filter chain of ffmpeg, so no scaling is available (man ffmpeg is a great source of information that you will not find on Google).

Ffmpeg scale