The purpose of this document is to address the recurring issue of mono audio in video assets as delivered to Global Media Production for introduction to the supply chain.
Mono Audio in Video
Global Media Production often receives video sources where audio does not have a distinct stereo image, aka “mono”. While there may be 2 tracks of audio the tracks are not panned left/ right and therefore the stereo image is null, acting as mono.
First please note the current policy regarding audio for video:
The mono audio issue is categorized as a gross error and is not passable into the ingestion system as per SME and DSP standards. Our guidelines suggest that where a stereo mixed master is available for any track, it must remain available in all products as stereo. Only in cases where no stereo master is available or the content was produced before 1987, can mono type audio be accepted.
The Mono Issue
It is believed the mono issue is originating from errant encoding on the post-production side of the project.
Understanding the cause of most of these issues is user error, we are providing a guideline below to avoid this mistake. The example below references Apple Corp’s popular nonlinear video editing software, Final Cut Pro (FCP), but the techniques and technical details can be applied to any NLE software or system.
How To Avoid Mono Audio in Video Delivery Sources
When importing video with audio or individual audio tracks in FCP, the application does not always properly assume the audio configuration. It will often import the audio as two separate tracks that automatically are center-panned. This may be related to user preference settings in the software but also seems to be dependent on how the source audio itself is configured. If exported this way without making changes, what may have been a stereo source will now render as null-stereo and will sound mono.
In the below graphic, the audio track is selected on the Timeline and the Modify > Stereo Pair option is selected to force the tracks to be left/ right panned and paired as a group.
In the next graphic, the Audio Mixer is highlighted showing the channels panning lever panned hard-left, and hard right. In addition the audio tracks on the Timeline now have small green arrows pointing to each other indicated the tracks are grouped together, as stereo paired.
Now, it is required the Project’s Sequence Settings are aligned with the intended audio configuration. Below, seen on the General tab, the Audio Settings have Config: Channel Grouped selected.
Finally, under the Audio tab, the Grouping selected is Stereo. This ensures that the Timeline tracks will remain as intended upon Export.
In short, the User must ensure the project is set up as stereo and that the audio is assigned out as panned stereo. Importing the source into the system and rendering it back out without checking is the probable root cause of these errors.