filter threads

In FFmpeg, filter threads refer to the number of threads that are used to execute video and audio filters during the processing of multimedia content. Filters are software components that can be used to apply various effects or transformations to audio and video streams, such as resizing, cropping, color correction, and noise reduction.

When FFmpeg applies filters to video or audio streams, it can use multiple threads to speed up the processing. This is especially useful when dealing with high-resolution videos or complex filter chains.

To enable filter threading in FFmpeg, you can use the `-filter_threads` option followed by the number of threads you want to use. For example, to use 4 threads for video filtering, you can use the following command:

ffmpeg -i input.mp4 -vf scale=1920:1080 -filter_threads 4 output.mp4

Note that not all filters support multithreading, and the effectiveness of using multiple threads will depend on the specific filter and hardware configuration. In general, using more threads can speed up the processing of complex filter chains, but it may also increase the memory usage and CPU load of the system.