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sessions.md

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Sessions

Sessions are the core abstraction for executing FFmpeg, FFprobe, and FFplay commands. Every execution in FFmpeg Kit Extended Flutter is tracked as a session.

Session Types

There are three primary session types, all inheriting from the base Session class:

  • FFmpegSession: Used for video and audio processing (FFmpeg commands).
  • FFprobeSession: Used for extracting media metadata (FFprobe commands).
  • FFplaySession: Used for media playback (FFplay commands).
  • MediaInformationSession: A specialized FFprobeSession optimized for MediaInformation retrieval.

Session Lifecycle

A session goes through several states during its lifecycle:

  1. Created: The session object exists but execution hasn't started.
  2. Running: The command is currently being executed.
  3. Completed: Execution finished normally (success or failure).
  4. Failed: Execution failed due to an error.

SessionState Enum

enum SessionState {
  created,
  running,
  completed,
  failed,
}

Base Session Methods

All session types provide the following methods:

  • getSessionId(): Returns the unique identifier for the session.
  • getState(): Returns the current SessionState.
  • getCommand(): Returns the command associated with the session.
  • getReturnCode(): Returns the exit code (available after completion).
  • getOutput(): Returns the full console output of the session.
  • getLogs(): Returns the session logs as a single string.
  • getFailStackTrace(): Returns the stack trace if the session failed.
  • getStartTime() / getEndTime(): Returns execution timestamps.
  • getSessionDuration(): Returns total execution time in milliseconds.
  • cancel(): Terminates the session if it is currently running.

Session Identification

You can identify the specific type of a session using these methods:

  • isFFmpegSession()
  • isFFprobeSession()
  • isFFplaySession()
  • isMediaInformationSession()

FFmpegSession

An FFmpegSession is specifically for processing tasks. It supports progress tracking through statistics.

FFmpegSession Features

  • Statistics: Access real-time encoding stats via onStatistics when using executeAsync.
  • Logs: Access detailed processing logs.

FFprobeSession

An FFprobeSession is for metadata extraction.

FFprobeSession Features

  • MediaInformation: If the session is a MediaInformationSession, you can use getMediaInformation() to retrieve structured metadata.

FFplaySession

An FFplaySession represents a playback instance.

FFplaySession Features

  • Playback Control: While FFplayKit provides global controls, individual FFplaySession objects also expose methods for pause(), resume(), and stop().
  • Playback Stats: Monitor current playback position and duration.

Return Codes

The return code indicates why a session finished:

  • ReturnCode.success (0): Execution finished successfully.
  • ReturnCode.cancel (255): Execution was cancelled by the user.
  • Other values: Indicate various FFmpeg/system error codes.

Check success using:

if (ReturnCode.isSuccess(session.getReturnCode())) {
  // Operation succeeded
}