Title: Theory / Unimportant / CS / command line / media / ffmpeg
Tags: computer_to_instruction fromCommandLine hasNotNewEffectReturnsMeaning récupéré FromVariables seen_description

Instruction: ffmpeg
Page: https://www.ffmpeg.org/ffmpeg.html
Effect: very fast video and audio converter that can also grab from a live audio/video source. It can also convert between arbitrary sample rates and resize video on the fly with a high quality polyphase filter.

Page: https://www.ffmpeg.org/ffmpeg.html
Effect: uses foo as an input file
Context: ffmpeg
Abbreviation: -i foo

Variable: i an integer
Meaning: the i-th input file, counting from 0
Page: https://www.ffmpeg.org/ffmpeg.html
Context: ffmpeg

Variable: i:j an integer
Meaning: the j-th stream from the i-th input file, counting from 0
Page: https://www.ffmpeg.org/ffmpeg.html
Context: ffmpeg

Question: An option applies
Answer: to only a single file, the next one
Page: https://www.ffmpeg.org/ffmpeg.html
Context: ffmpeg

Name: demuxer
Definition: Transform a multimedia file into its encoded data packets
Page: https://www.ffmpeg.org/ffmpeg.html

Name: muxer
Definition: Transform an encoded data packets into multimedia file
Page: https://www.ffmpeg.org/ffmpeg.html

Name: decoder
Definition: Transform an encoded data packets into decoded frames
Page: https://www.ffmpeg.org/ffmpeg.html

Name: encoder
Definition: Transform decoded frames into an encoded data packets
Page: https://www.ffmpeg.org/ffmpeg.html

Question: How do ffmpeg synchronize multiple input files ?
Answer: tracking lowest timestamp on any active input stream
Page: https://www.ffmpeg.org/ffmpeg.html

Name: Simple filtergraphs
Definition: Filtergraph with exactly one input and output, both of the same type.
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 3
Section: 1.1

Fla: -filter
Effect: configure simple filtergraph
Page: https://www.ffmpeg.org/ffmpeg.html
Prefix: ffmpeg
Chapter: 3
Section: 1.1

Fla: -vf
Effect: configure simple filtergraph for video
Page: https://www.ffmpeg.org/ffmpeg.html
Prefix: ffmpeg
Chapter: 3
Section: 1.1

Fla: -af
Effect: configure simple filtergraph for audio
Page: https://www.ffmpeg.org/ffmpeg.html
Prefix: ffmpeg
Chapter: 3
Section: 1.1

Name: Complex filtergraph
Definition: A filtergraph which cannot be described as simply a linear processing chain applied to one stream.
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 3
Section: 1.2
Context: ffmpeg

Fla: -filter_complex
Effect: configure a complex filtergraph
Page: https://www.ffmpeg.org/ffmpeg.html
Prefix: ffmpeg
Chapter: 3
Section: 1.2

Fla: -codec:copy
Effect: Omit encoding/decoding part, copy encoded data packets
Page: https://www.ffmpeg.org/ffmpeg.html
Prefix: ffmpeg
Chapter: 3
Section: 1.2

Question: By default, the video stream choosen is
Answer: the one of highest resolution
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 4
Context: ffmpeg

Question: By default, the audio stream choosen is
Answer: the one with most channels
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 4

Question: By default, the subtitle stream choosen is
Answer: the first one
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 4

Name: A stream specifier
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 4
Representation: a string generally appended to the option name and separated from it by a colon

Question: Meaning of the empty string specifier
Answer: match all stream
Page: https://www.ffmpeg.org/ffmpeg.html
Chapter: 4

Instruction: ffprobe
Page: https://www.ffmpeg.org/ffprobe.html
Effect: Gathers information from multimedia streams and prints it in human- and machine-readable fashion.
Return positive value if input is not a media

Instruction: ffplay
Page: https://www.ffmpeg.org/ffprobe.html
Effect: very simple and portable media player using the FFmpeg libraries and the SDL library