Redirect FFprobe stdout to JSON Keeping stderr

This guide explains how to export ffprobe metadata into a JSON file by redirecting standard output (stdout) while keeping diagnostic logs and standard error (stderr) visible in your terminal console. You will learn the exact shell syntax for stream redirection and the required ffprobe parameters to produce clean JSON files on Linux, macOS, and Windows.

Understanding the Streams in FFprobe

By default, command-line shells manage output using separate data streams:

  • Standard Output (stdout / File Descriptor 1): The stream where ffprobe outputs the requested structured data, such as JSON or XML.
  • Standard Error (stderr / File Descriptor 2): The stream where ffprobe displays application logs, banners, warnings, and error messages.

Because these streams are separated by default, directing standard output to a file does not capture or hide standard error unless you explicitly merge them.

The Command Syntax (Linux, macOS, and Windows CMD)

To capture the JSON output to a file while leaving error and log messages in the terminal, redirect only file descriptor 1 using the > operator:

ffprobe -v error -show_format -show_streams -of json input.mp4 > output.json

If you prefer to be explicit with file descriptors, specify 1>:

ffprobe -show_format -show_streams -of json input.mp4 1> output.json

Breakdown of Arguments:

  • -of json (or -print_format json): Instructs ffprobe to format the requested metadata into valid JSON and write it directly to stdout.
  • -show_format: Extracts container-level metadata (duration, bitrate, tags).
  • -show_streams: Extracts individual stream metadata (codec details, resolution, audio channels).
  • input.mp4: The target media file.
  • > output.json: Redirects stream 1 (stdout) to output.json. Stream 2 (stderr) remains attached to the terminal window.

Controlling the Verbosity of stderr

If you want to maintain the stderr stream for monitoring while preventing normal program banner clutter, use the -v (verbosity) flag:

  • Show only critical errors:

    ffprobe -v error -show_format -show_streams -of json input.mp4 > output.json

  • Show warnings and errors:

    ffprobe -v warning -show_format -show_streams -of json input.mp4 > output.json

  • Show full diagnostic logs without the build configuration banner:

    ffprobe -hide_banner -v info -show_format -show_streams -of json input.mp4 > output.json

In all cases, any warning or error produced by the decoder will print directly to your screen, and only valid JSON will be written to output.json.

PowerShell Syntax (Windows)

PowerShell handles native command redirection slightly differently. In PowerShell 5.1 and newer, use the explicit stream indicator:

ffprobe.exe -v error -show_format -show_streams -of json input.mp4 1> output.json

If you experience character encoding issues with PowerShell's redirection operators, use the raw byte pipeline instead:

ffprobe.exe -v error -show_format -show_streams -of json input.mp4 | Out-File -FilePath output.json -Encoding utf8

Because Out-File only receives objects from the success stream (stdout), errors and warnings sent to stderr will continue to render directly in the PowerShell console.