Fundamentals of Audio/Video Encoding and ffmpeg Command Basics

ffmpeg is a leading multimedia processing framework that supports encoding, decoding, transcoding and runs on Linux, macOS and Windows.

Video files use container formats (e.g., avi, rmvb, mp4, flv, mkv) that package audio and video streams; tools like MediaInfo reveal details such as resolution, bitrate and frame rate.

Bitrate (bits per second) determines data flow; higher bitrate yields clearer video. Frame rate (FPS) measures frames displayed per second and affects smoothness, especially in games.

Key performance indicators for live streaming include latency (time difference between send and receive), stutter rate (number of playback interruptions), and first‑frame time (time to display the first decoded frame).

Common ffmpeg command‑line options include -i for input file, -b:v to set video bitrate, -s for resolution, -r for frame rate, -c:v libx264 for H.264 encoding, and -re to send at native frame rate.

Example commands:

Stream: ffmpeg -re -i localFile.mp4 -c copy -f flv rtmp://ps0.xxx.com/xxx

Play stream: ffplay http://pl0.xxx.com/xxx/xxx.flv

Transcode to H.264 MP4: ffmpeg -i D:/test.mov -c:v libx264 -strict -2 D:/test.mp4

Change bitrate: ffmpeg -i test.mp4 -b:v 1500k testk.mp4

Change resolution: ffmpeg -i D:/test/test.mp4 -s 800x600 D:/test/testf.mp4

Change frame rate: ffmpeg -i D:/test/test.mp4 -r 25 D:/test/testr.mp4

Probe stream info: ffprobe http://pl0.xxx.com/xxx/xxx.flv

For more details, refer to the official ffmpeg website: http://ffmpeg.org/.