Concat Workflow Operation Handler

Overview

The "concat" operation handler has been created to concatenate multiple video tracks into one video track. Note, that the concatenation process used will always re-encode the videos.

The internal ffmpeg command is using the following filters: fps, scale, pad and setdar for scaling all videos to a similar size including letterboxing, aevalsrc for creating silent audio streams and of course the concat for the actual concatenation step.

FFmpeg Filter Example

-filter_complex '
  [0:v]fps=fps=25.0,scale=iw*min(640/iw\,480/ih):ih*min(640/iw\,480/ih),pad=640:480:(ow-iw)/2:(oh-ih)/2,setdar=4:3[b];
  [1:v]fps=fps=25.0,scale=iw*min(640/iw\,480/ih):ih*min(640/iw\,480/ih),pad=640:480:(ow-iw)/2:(oh-ih)/2,setdar=4:3[c];
  [2:v]fps=fps=25.0,scale=iw*min(640/iw\,480/ih):ih*min(640/iw\,480/ih),pad=640:480:(ow-iw)/2:(oh-ih)/2,setdar=4:3[d];
  aevalsrc=0::d=1[silent];
  [b][0:a][c][silent][d][2:a]concat=n=3:v=1:a=1[v][a]' -map '[v]' -map '[a]'

Usage

This operation is quite similar to the compose operation. The only difference is that the input properties are not only limited to one source-flavor and source-tag. The operation supports multiple flavor and tags as input. To add multiple source, add different key with the prefix source-flavor-/source-tag- and an incremental number starting with 0. For example:

• source-flavor-part-0
• source-flavor-part-1
• source-flavor-part-..

Configuration Keys

Key	Required	Description	Default	Example
source-flavor-part-X	false	An iterative list of part/flavor to use as input track.	NULL	presenter/trimmed
source-tag-part-X	false	An iterative list of part/tag to use as input track.	NULL	source-to-concate
source-flavor-part-X-mandatory	false	Define the flavor part-X as optional for concatenation.	false	true
source-tag-part-X-mandatory	false	Define the tag part-X as optional for concatenation.	false	true
encoding-profile	true	Encoding profile to use for the concatenation.	NULL	concat
target-flavor	true	Flavor(s) to add to the output track.	NULL	presenter/concat
target-tags	false	Tag(s) to add to the output track	NULL	engage-download
output-resolution	true	Output resolution in width, height or a source part	NULL	1900x1080, part-1
output-framerate	false	Output frame rate in frames per second or a source part	-1.0	25, 23.976, part-1

Example

Example of a concat operation in a workflow definition.

<!-- Add intro and outro part to the presenter track -->
<operation
  id="concat"
  fail-on-error="true"
  exception-handler-workflow="error"
  description="Concatenate the presenter track and the intro/outro videos.">
  <configurations>
    <configuration key="source-flavor-part-0">intro/source</configuration>
    <configuration key="source-flavor-part-1">presenter/trimmed</configuration>
    <configuration key="source-flavor-part-1-mandatory">true</configuration>
    <configuration key="source-flavor-part-2">outro/source</configuration>
    <configuration key="target-flavor">presenter/concat</configuration>
    <configuration key="target-tags">engage-download,engage-streaming</configuration>
    <configuration key="encoding-profile">concat</configuration>
    <configuration key="output-resolution">1920x1080</configuration>
    <configuration key="output-framerate">part-1</configuration>
  </configurations>
</operation>

Encoding Profile

The encoding profile command must contain the the #{concatCommand} parameter.

profile.concat.name = concat
profile.concat.input = visual
profile.concat.output = visual
profile.concat.suffix = -concatenated.mp4
profile.concat.mimetype = video/mp4
profile.concat.ffmpeg.command = #{concatCommand} \
  -c:a aac -b:a 128k \
  -c:v mpeg4 -b:v 1200k -flags +aic+mv4 \
  #{out.dir}/#{out.name}#{out.suffix}