Command Structure and Syntax

The fundamental syntax for FFmpeg follows a pattern where global options precede input files, input-specific options precede the -i flag, and output-specific options precede the output filename.

ffmpeg [global_options] [input_options] -i input_file [output_options] output_file

By default, FFmpeg attempts to perform lossless conversion, maintaining the same audio and video parameters as the source material unless specified otherwise.

Video Transcoding and Format Conversion

To convert video containers without re-encoding the streams (fast process), use the copy codec. This is useful for changing containers like MP4 to MKV.

ffmpeg -i source_video.mp4 -c:v copy -c:a copy output_video.mkv

To re-encode video using specific codecs, such as converting an older file to H.264:

ffmpeg -i input.avi -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4

Converting to HLS segments for adaptive streaming requires creating a playlist and segment files:

ffmpeg -i movie.mp4 -c:v libx264 -c:a aac -f hls -hls_time 4 -hls_list_size 0 -hls_segment_filename segment_%03d.ts stream.m3u8

Stream Extraction and Processing

Separating audio from video allows for dedicated audio processing. The -vn flag disables video recording.

ffmpeg -i multimedia_file.mp4 -vn -acodec copy audio_only.aac

Conversely, to extract video without audio (disabling audio with -an):

ffmpeg -i multimedia_file.mp4 -an -vcodec copy video_only.h264

To extract specific frames from a video as images, use the image2 muxer:

ffmpeg -i clip.mp4 -r 1 -f image2 snapshot_%03d.png

Video Filtering and Manipulation

FFmpeg provides powerful filtering capabilities via the -vf (video filter) option. To resize a video while maintaining aspect ratio, use the scale filter with a value of -1 for the height to calculate it automatically.

ffmpeg -i original.mp4 -vf scale=1280:-1 -c:a copy resized.mp4

To overlay a watermark image onto a video, use the overlay filter. This example places the logo 10 pixels from the top-left corner.

ffmpeg -i main_video.mp4 -i logo.png -filter_complex "overlay=10:10" watermarked_video.mp4

Trimming a video segment without re-encoding is efficient. The following command cuts from 10 seconds to 20 seconds.

ffmpeg -ss 00:00:10 -i input.mp4 -t 00:00:10 -c copy segment.mp4

Network Streaming Protocols

FFmpeg can push streams to various network protocols. To stream a file via UDP:

ffmpeg -re -i local_file.ts -c copy -f mpegts udp://192.168.1.50:1234

For publishing to an RTMP server (common for live streaming ingestion), the syntax typically involves the FLV format.

ffmpeg -re -i source_video.mp4 -c copy -f flv rtmp://live-server/app/stream_key

Audio Processing Options

Audio files can be converted and processed. To change the sampling rate of a WAV file to MP2:

ffmpeg -i input_audio.wav -ar 44100 output_audio.mp2

Adjusting volume can be done using the volume filter. The example below increases volume by 2.0 (double).

ffmpeg -i quiet_track.mp3 -af "volume=2.0" loud_track.mp3