Encode Workflow Operation

ID: encode

Parallel FFmpeg encoding

Description

The encode workflow operation can be used to encode media files to different formats using FFmpeg.

It can utilize the parallel encoding capabilities of FFmpeg. This has the advantage that the source file needs to be read only once for several encodings, reducing the encoding time quite a lot. Additionally, this will let FFmpeg make better use of multiple CPU cores.

Parameter Table

configuration keys	example	description
source-flavor¹	presenter/work	Single flavor specifying media to be encoded
source-flavors¹	presenter/work,presentation/work	Comma-separated list of flavors specifying media to be encoded
target-flavor	presenter/delivery	Flavor of the new media
source-tags	sometag	Comma-separated list of tags of media to encode
target-tags	sometag	Comma-separated list of tags to be assigned to the new media
encoding-profile	parallel.http	Encoding profile to use

¹If source-flavours are specified, media of these flavors are considered, if not, media matching the source-flavour configuration option is considered.

As explained in the "Encoding Profile Example" section, every media file created by an encode operation has its own named suffix. The suffix name is defined in the encode profile definition. It will be added as a tag to the corresponding track in the media package. This is different from the target-tags workflow operation parameter, which will cause the specified tag list to be added to every media file created by the operation.

For instance, let us take the example operation and encoding profile defined in this documentation. After a successful run of the operation, the media package will contain four new tracks: the first one containing the new tags engage-download, engage-streaming and low-quality; the second one containing the new tags engage-download, engage-streaming and medium-quality; etc.

Operation Example

<operation
    id="encode"
    description="encoding media files">
  <configurations>
    <configuration key="source-flavor">*/trimmed</configuration>
    <configuration key="target-flavor">*/delivery</configuration>
    <configuration key="target-tags">engage-download,engage-streaming</configuration>
    <configuration key="encoding-profile">parallel.http</configuration>
  </configurations>
</operation>

Encoding Profile Example

Unlike a regular compose operation, this operation can generate more than one output file and, therefore, more than one media package track elements. In order to distinguish these tracks, the encoding profile syntax for this operation allows different named suffix parameters in the form of <profile_name>.suffix.<suffix_name> = <suffix_value>.

Because file names are irrelevant for the workflow operations, each suffix name is added as a tag to the corresponding media package element. For instance, if a media file with a filename of myfile.ext is processed with the encoding profile in the example below, the first output file will be myfile-low.mp4 and the resulting media package element will contain a tag with the value low-quality; the second output file will be myfile-medium.mp4 and the resulting media package element will contain a tag with the value medium-quality; and so on.

# Distribution format definition for low quality presenter download
profile.parallel.http.name = parallel video encoding
profile.parallel.http.input = visual
profile.parallel.http.output = visual
profile.parallel.http.suffix.low-quality = -low.mp4
profile.parallel.http.suffix.medium-quality = -medium.mp4
profile.parallel.http.suffix.high-quality = -high.mp4
profile.parallel.http.suffix.hd-quality = -hd.mp4
profile.parallel.http.ffmpeg.command = -i #{in.video.path} \
  -c:v libx264 -filter:v scale=-2:288 -preset slower -crf 28 -r 25 -profile:v baseline -tune film -movflags faststart \
  -c:a aac -ar 22050 -ac 1 -ab 32k #{out.dir}/#{out.name}#{out.suffix.low-quality} \
  -c:v libx264 -filter:v scale=-2:360 -preset slower -crf 25 -r 25 -profile:v baseline -tune film -movflags faststart \
  -c:a aac -ar 22050 -ac 1 -ab 48k #{out.dir}/#{out.name}#{out.suffix.medium-quality} \
  -c:v libx264 -filter:v scale=-2:576 -preset medium -crf 23 -r 25 -pix_fmt yuv420p -tune film  -movflags faststart \
  -c:a aac -ar 44100 -ab 96k #{out.dir}/#{out.name}#{out.suffix.high-quality} \
  -c:v libx264 -filter:v scale=-2:720 -preset medium -crf 23 -r 25 -pix_fmt yuv420p -tune film  -movflags faststart \
  -c:a aac -ar 44100 -ab 96k #{out.dir}/#{out.name}#{out.suffix.hd-quality}

Resolution Based Encoding

The encode operation supports encoding based on the input video's resolution. For example, you can encode a certain output resolution only for high resolution inputs. For this you can define conditionally set variables like if-height-geq-720 as part of the ffmpeg.command property which retain their value only if the video resolution meets the defined criteria. This variable can then be used in the ffmpeg.command property.

This modification to the encoding profile from above will encode the 720p output only if the input height is at least 720 pixels, note the Reference #{if-height-geq-720} to the variable at the end of the ffmpeg.command property:

…
profile.parallel.http.ffmpeg.command.if-height-geq-720 = -c:v libx264 -filter:v scale=-2:720 \
  -preset medium -crf 23 -r 25 -pix_fmt yuv420p -tune film  -movflags faststart \
  -c:a aac -ar 44100 -ab 96k #{out.dir}/#{out.name}#{out.suffix.hd-quality}
profile.parallel.http.ffmpeg.command = -i #{in.video.path} \
  …
  -c:v libx264 -filter:v scale=-2:576 -preset medium -crf 23 -r 25 -pix_fmt yuv420p -tune film  -movflags faststart \
  -c:a aac -ar 44100 -ab 96k #{out.dir}/#{out.name}#{out.suffix.high-quality} \
  #{if-height-geq-720}

There are currently two resolution based conditionally set variables supported:

Variable	Example	Description
if-height-geq-<height>	if-height-geq-720	The value is set if the height of the video is greater or equal to <height> pixels.
if-width-or-height-geq-<width>-<height>	if-width-or-height-geq-1280-720	The value is set if the width of the video is greater or equal to <width> or if the height is greater or equal to <height>.
if-height-lt-<height>	if-height-lt-480	The value is set if the height of the video is less than <height> pixels.