Channel Replacement or Extraction
In multi-language broadcast, media files are often supplied, with a separate WAV containing a required language track. The challenge is to insert the audio from the WAV directly in to the media file so that the playout system doesn’t need to be modified. You might have the alternative problem – you want to pull the Mix & Effects (M&E) out of a media file, but want your creative talent to spend their time on making a good mix using the M&E, and not wasting their time and on simply extracting the audio in the edit suite.
Both functions can be done in a fully automated fashion, and many times faster than real time, using the Channel replacement/Extraction option within Engine.
This function lets you take your media file, and replace some of the audio within that file, with audio taken from AIFF or WAV files.
The format of the main media file, and of the AIFF/WAV file(s) is flexible. For example, the media file can have up to 64 tracks of audio, and can be a mix of PCM and Dolby E. The AIFF/WAV files can be mono, stereo, or multi channel, and can also be a mix of PCM and Dolby E. Engine prevents you accidentally breaking a Dolby E pair by only changing half of the pair, but aside from that, tracks containing Dolby E can be manipulated with the same flexibility as PCM tracks.
Watch this short guide to setting up workflows for track replacement
In the following workflow example, the main media file has 8 channels of audio. We are replacing channels 3 & 4 from the original file with the contents of a stereo WAV.
This example is typical of a language replacement workflow. You might have a file with English on channels 1&2, French on 3&4, and you have been supplied with a German language WAV. This workflow will replace the French track with the German track. Note that this can be carried out in conjunction with all other Engine features if required. For example, this next workflow shows Engine performing Loudness Compliance on the original channels 1&2 as well as the replaced 3&4, followed by Dolby E encoding and then channel replication.
An alternative use for channel replacement is to add a premixed audio description commentary into the main media file, and this could be done with the same workflow.
Often broadcast workflows use stereo WAV files, even when dealing with 5.1 and whilst this can be very efficient once in this format, it frequently requires passing the file through a transcoder to provide the correct formats. However you can now do this directly inside Engine.
Engine can produce multiple output files from a source media file, even if the source file only had two channels. In this example, the main input to Engine is a stereo MXF file containing 5.1 data that has been Dolby E encoded. The workflow decodes the Dolby, and creates three stereo PCM WAV files, containing L & R, C & LFE, and Ls & Rs.
Another good example of where this technique is useful within a Broadcast workflow, is for Upmix. Again you could start with a stereo WAV, then upmix to 5.1, and create three output WAV files, again containing L & R, C & LFE, and Ls & Rs.
However Engine has more flexibility than only extracting tracks at the end of a workflow. In this example, the results of upmix are extracted as three stereo WAV files, but the full upmix is then Dolby E encoded, giving one stereo WAV file containing the Dolby E, in addition to the upmix as separate components. The level of choice within Engine means it can save a great deal of time in your workflow, by giving everything you need without needing to use extra tools.