Limecraft Flow provides extensive support for multitrack or multi-channel audio, and for using different audio track layout configurations. This article explains how to setup your production to allow the use of multi-channel audio.
TABLE OF CONTENTS
Introduction
In another article we explain audio metadata, which is stored in the audio layout of the clip. It allows you to indicate up to four channel layouts (5.1 french + stereo french + 5.1 original + stereo original). The Limecraft browser-based player supports switching between audio channel layouts, but it requires a proper configuration of the production, as support for multi-channel audio requires specific definition and storage of proxies.
To get full multitrack support, in which the video player is able to switch between the channel layouts, the ingest process needs to be properly configured on the production. It is necessary to set the ingest preset in ‘Ingest Configuration’ settings to ‘multitrack’, see ‘Ingest configuration’. The player will then show a toggle menu in which you can switch between the audio of the different channel layouts.
Step 1 - Enable multitrack Audio
To enable the multitrack support for the production, go to Production Settings > Ingest Settings and change the selected Ingest preset to ‘Multitrack’. More information is in the ‘Ingest configuration’ section below.
Step 2 - Ingest configuration
The Ingest configuration screen gives an overview of how Flow treats incoming material to prepare it for playout in the browser. You can access Ingest Configuration via Production Settings > Ingest.
You are presented with an overview of the Flow ingest process, which might look like this:
This diagram shows three transcode slots. The top one is always executed before the others, as indicated by the green down-arrow icon. It can be used to generate media which serves as the input for the next two slots. These next two slots are executed in parallel (as indicated by the green plus icon).
The screenshot above uses abstract labels like ‘Source’, ‘Output 1’ etc., but in practice, these will point to encoder profiles.
Transcode slots and profiles
The ingest configuration defines which versions of your material will be created during Flow ingest.
Let’s start with an overview of some of the built-in profiles:
The ingest configuration is done by assigning these profiles to the available (3) transcode slots of the ingest process.
Today, we don’t allow freely filling in these slots. You can only toggle between the provided ingest presets.
Ingest presets
The default configuration looks like this:
When new material is uploaded to Limecraft Flow, it will run the Flow ingest. The first transcode slot (which is run before everything else) is not used in the default ingest preset. Only the two parallel slots are used. When the material is of type RAW, MEZZANINE or PROXY, two versions will be created: the web proxy, and the low-res web proxy.
However, when working with multitrack audio, you should use a different preset. Click the green change button, select multitrack and confirm.
The ingest configuration now looks like this:
When new material is presented to Flow, it will:
first create a mezzanine proxy from the material. This is a bit like a web proxy, but with all audio channels still present (no down mixing). The next transcode slot will wait for this to finish.
Once the mezzanine proxy has been created, create a dynamic proxy out of it. The latter can be played out in the Limecraft player and supports switching between the audio of different channel layouts.
Note: when sending material from Edge to Flow, it is advised to send the mezzanine proxy. The mezzanine proxy has a low enough bitrate to make the transfer fast, but still contains all the audio channels. Flow will then create the dynamic proxy from the mezzanine proxy.
If a clip’s audio layout contains multiple channel layouts, the player control bar will show a menu (with the cog icon) in which you can toggle between the different channel layouts:
