FFmpeg filter_complex Explained: Multi-Input Processing and Filter Chains

FFmpeg's -vf flag is limited to single-stream operations, but filter_complex allows multi-input and multi-output processing. It uses labels to route streams and can chain filters across different streams. To use filter_complex, create labels for input and output streams, and use -map to route labeled streams to output files. This guide breaks down the syntax and patterns for filter_complex.