FFMPEG

Stream Information

ffmpeg -i input.mkv
ffprobe input.mkv

-hide_banner: Hides the banner information from all commands

MKV to MP4

ffmpeg -i input.mkv -c copy output.mp4
 
# Select specific streams
ffmpeg -i input.mkv -map 0:0 -map 0:2 -c copy output.mp4

-map: Select specific streams

Extract Subtitles

ffmpeg -i input.mkv -map 0:2 -c copy output.srt
 
# Covert other formats (ASS/SSA) to SRT
ffmpeg -i input.mkv -map 0:2 -codec:s srt output.srt

-codec: Used when stream have to be converted to a different format
-c copy: Export the stream in raw (original) format

Extract Audio as MP3

# VBR Conversion
ffmpeg -i input.mkv -map 0:1 -codec:a libmp3lame -qscale:a 0 output.mp3
 
# CBR Conversion
ffmpeg -i input.mkv -map 0:1 -codec:a libmp3lame -bitrate 192k output.mp3

For VBR:
0: Best quality large file size
9: Worst quality small file size

If the audio is already in MP3 no conversion is required

Format	Best Encoder	Use Case
MP3	libmp3lame	High-quality audio for general use, wide compatibility
AAC	libfdk_aac	Better quality than MP3, popular in streaming and mobile devices
OGG	libvorbis	Open-source, high-quality audio, often used in streaming
FLAC	libflac	Lossless audio for archiving, professional applications
WAV	pcm_s16le	Uncompressed, high-quality audio for professional applications
Opus	libopus	Superior quality for streaming, VoIP, and real-time communication

Trim Video

ffmpeg -i input.mp4 -ss 00:00:10 -to 00:00:30 -c copy segment1.mp4

Combine Videos

ffmpeg -f concat -safe 0 -i filelist.txt -c copy output.mp4

Without -i the input filenames can be listed directly