fluent-plugin-audio-transcoder

Fluentd filter plugin to transcode audio files using FFmpeg.

Overview

This plugin transcodes audio binary content according to specified parameters and re-emits the processed content. It uses FFmpeg for audio transcoding, allowing for volume normalization and format conversion to optimize files for speech-to-text processing.

Installation

Requirements

• Ruby 3.4.1 or higher
• FFmpeg installed and accessible in the system path
• Fluentd v0.14.10 or higher

RubyGems

$ gem install fluent-plugin-audio-transcoder

Bundler

Add the following line to your Gemfile:

gem 'fluent-plugin-audio-transcoder'

And then execute:

$ bundle

Configuration

Filter Configuration

<filter your.tag.here>
  @type audio_transcoder
  
  # FFmpeg transcoding options (optional)
  transcode_options -c:v copy -af loudnorm=I=-14:TP=0.0:print_format=summary
  
  # Output file extension (optional)
  output_extension aac
  
  # Path for temporary buffer files
  buffer_path /path/to/buffer/directory
</filter>

Parameters

Parameter	Type	Description	Default
transcode_options	string	FFmpeg command-line options for transcoding including filters	-c:v copy -af loudnorm=I=-14:TP=0.0:print_format=summary
output_extension	string	File extension for the transcoded file	aac
buffer_path	string	Path for temporary files used during transcoding	/tmp/fluentd-audio-transcoder

Input/Output

Input Record Fields

The plugin expects the following fields in the incoming record:

• path: Full path to the audio file (used for filename)
• content: Binary content of the audio file

Output Record Fields

The plugin modifies the following fields in the output record:

• path: Full path to the transcoded audio file
• content: Binary content of the transcoded audio file
• size: Size of the transcoded audio file in bytes

Other fields in the record remain unchanged.

Example

<filter audio.**>
  @type audio_transcoder
  transcode_options -c:v copy -af loudnorm=I=-16:TP=-1.5:print_format=summary
  output_extension mp3
  buffer_path /var/log/fluentd/audio_buffer
</filter>

This configuration will normalize the audio volume to -16 LUFS and convert it to MP3 format.

Note

• The plugin creates temporary files in the specified buffer_path during processing. These files are not automatically deleted after processing and should be managed separately if needed.
• This plugin does not modify the tag of events as it follows the standard filter plugin behavior.

Development

After checking out the repo, run bundle install to install dependencies. Then, run rake test to run the tests.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/bash0C7/fluent-plugin-audio-transcoder.

License

The gem is available as open source under the terms of the Apache-2.0 License.