Concat workflow operation handler

FFMPEG 1.1 is required for the encoding profile related to this operation!


The "concat" operation handler has been created to concatenate multiple video tracks into one video track. The concatenation process uses the ffmpeg scale filter which is always re-encoding the videos, this means the resulting video has most likely a loss of quality.


The internal ffmpeg command is using the following filters: 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. More info can be found here:

Sample complex concat filter command

-filter_complex "[0:v]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]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]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]'


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

Configuration keys

Key Required Description Default Value 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 an optional track for concatenation. false
source-tag-part-X-mandatory false Define the tag part-X as an optional track for concatenation. false true
encoding-profile true Define the encoding-profile to use for the concatenation operation. See example of profile below. NULL concat
target-flavor true Define the flavor(s) to add to the output track. NULL presenter/concat
target-tags false Define the tag(s) to add to the output track NULL engage-download
output-resolution true Define the output resolution in width, height or take it from one of the given parts NULL 1900x1080, part-1


Example of an concat operation in a workflow definition.

<!-- Add intro and outro part to the presenter track -->
  description="Concatenate the presenter track and the intro/outro videos.">
    <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>

Encoding profile

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

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