Audio Normalization Workflow Operation

ID: normalize-audio

Description

This operation normalizes the first audio stream of a video or audio track through SoX, it creates a new track with a reference to the original track which can be flavored and tagged. It can be used with audio and/or video files, at least one audio stream must be available otherwise nothing happens. Here are the internal steps done by the different inputs:

Used with Audio only file (forceTranscode is deactivated):

Check if necessary RMS Lev dB value is already in the track's metadata. If not run audio analyzation.
Run audio normalization with original audio file.
Replace the normalized audio file with the original.
Write analyzed audio metadata to the track's mediapackage.
Delete all used temporary files.

Used with Audio only file and forceTranscode activated:

Check if necessary RMS Lev dB value is already in the track's metadata. If not run audio analyzation.
(forceTranscode step) Encode audio to FLAC. (Must be used when given audio file format is not supported by SoX)
Run audio normalization with original audio file or encoded FLAC audio file.
(forceTranscode step) Mux normalized audio file back to the original audio container by replacing it with the original audio stream.
Write analyzed audio metadata to the track's mediapackage.
Delete all used temporary files

Used with Video file:

Extract audio file encoded as FLAC audio and save it temporary in a collection
Check if necessary RMS Lev dB value is already in the track's metadata. If not run audio analyzation.
Run audio normalization with extracted audio file.
Mux normalized audio file back to the original video container by replacing it with original audio stream.
Write analyzed audio metadata to the track's mediapackage.
Delete all used temporary files

Example result track:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track ref="track:track-2" type="presenter/normalized" id="70626874-17d2-480d-9d30-c10f0824961c">
  <mimetype>audio/x-flv</mimetype>
  <tags>
    <tag>norm</tag>
  </tags>
  <url>http://localhost:8080/files/mediapackage/8a510168-9102-425f-81e9-0943774dd229/70626874-17d2-480d-9d30-c10f0824961c/demo_slide_video_6min_buss.flv</url>
  <checksum type="md5">4e30d7d4305b0793f301816e796471db</checksum>
  <duration>414407</duration>
  <audio id="audio-1">
    <device/>
    <encoder type="MPEG Audio"/>
    <bitdepth>16</bitdepth>
    <channels>2</channels>
    <bitrate>64000.0</bitrate>
    <peakleveldb>-4.03</peakleveldb> <!-- NEW -->
    <rmsleveldb>-30.54</rmsleveldb> <!-- NEW -->
    <rmspeakdb>-10.85</rmspeakdb> <!-- NEW -->
  </audio>
</track>

Parameter Table

configuration keys	example	description	default value
source-flavors	"presentation/work,presenter/work"	The "flavors" of the track to use as a source input	EMPTY
source-flavor	"presentation/work"	The "flavor" of the track to use as a source input	EMPTY
source-tags	"engage,atom,rss"	The "tag" of the track to use as a source input	EMPTY
target-flavor	"presentation/normalized"	The flavor to apply to the normalized file	EMPTY
target-tags	"norm"	The tags to apply to the normalized file	EMPTY
target-decibel*	-30.4	The target RMS Level Decibel	EMPTY
force-transcode	"true" or "false"	Whether to force transcoding the audio stream (This is needed when trying to strip an audio stream from an audio only video container, because SoX can not handle video formats, so it must be encoded to an audio format)	FALSE

* required keys

Operation Example

<operation
    id="normalize-audio"
    description="Normalize audio stream">
  <configurations>
    <configuration key="source-flavor">*/work</configuration>
    <configuration key="target-flavor">*/normalized</configuration>
    <configuration key="target-tags">norm</configuration>
    <configuration key="target-decibel">-30</configuration>
    <configuration key="force-transcode">true</configuration>
  </configurations>
</operation>

Missing Encoding Profiles

Some of the encoding profiles necessary for this operation are not included in Opencast per default, but the operation will not work without them. You need to include the following encoding profiles by copy and pasting them in a .properties file in the etc/encoding folder of your installation.

# SoX Audio only (strip video)
profile.sox-audio-only.work.name = sox audio only
profile.sox-audio-only.work.input = visual
profile.sox-audio-only.work.output = audio
profile.sox-audio-only.work.suffix = -work.flac
profile.sox-audio-only.work.ffmpeg.command = -i #{in.video.path} -vn -c:a flac #{out.dir}/#{out.name}#{out.suffix}

# SoX replace Audio (replace audio)
profile.sox-audio-replace.work.name = sox replace audio
profile.sox-audio-replace.work.input = visual
profile.sox-audio-replace.work.output = visual
profile.sox-audio-replace.work.suffix = -work.#{in.video.suffix}
profile.sox-audio-replace.work.ffmpeg.command = -i #{in.audio.path} -i #{in.video.path} -map 1:v -map 0:a -c:v copy #{out.dir}/#{out.name}#{out.suffix}