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.



Limecraft supports switching between audio channel layouts while playing out. Using multi-channel audio and switching between audio layouts assumes proper configuration of the production, as support for multi-channel audio requires specific definition and storage of proxies. This article explains the basic setup of multi-channel audio in general. For more information on the specific setup of audio channel layouts, please refer to the appropriate section

Limecraft Flow supports multiple audio layout configurations

To get full support for multi-channel audio, in which the video player is able to switch between the channel layouts, the ingest process needs to be properly configured on the level production. It is necessary to set the ingest preset in ‘Ingest Configuration’ settings to ‘multitrack’. 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.

Limecraft screenshot detail illustrating how to enable multi-channel audio

Limecraft screenshot detail illustrating how to enable multi-channel audio

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 schematic overview of the Flow ingest process, which might look like this:

Limecraft screenshot detail illustrating how you can manipulate the processing sequence of the different steps of the ingest process

In this example, the video ingest process consists of 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:



Web Proxy

The default h264 web proxy which is generated for playing material in the html5 video player. The resolution will be limited to 1280x720 and the bitrate to 2Mbps.

The audio is a stereo mix, where the uneven channels are all mixed to the left and the even channels are all mixed to the right.

Low res web proxy

A scaled-down version of the web proxy profile. The resolution will be limited to 768x432 and the bitrate to 1Mbps. This is useful when the network bandwidth is limited.

The audio is a stereo mix, where the uneven channels are all mixed to the left and the even channels are all mixed to the right.

Mezzanine proxy

This is an intermediate format used in multitrack audio scenarios. It is not directly playable in the browser. The video is similar to the web proxy, but the audio will still contain each audio track of the original. This intermediate version can be used to generate web proxies having a different audio mix.

Dynamic proxy

Dynamic proxies contain multiple versions to allow the player to switch between different versions while playing out. This profile has video which is similar to the web proxy. The audio is based on the audio layout property of the clip. A playable version is created per channel layout. The player will show a toggle menu to switch between the different channel layouts.

The ingest configuration is done by assigning these profiles to the available (3) transcode slots of the ingest process. Limecraft doesn't allow freely filling in these slots. You can only toggle between the provided ingest presets. 

Defining Ingest Presets to create proxies with Multi-channel Audio

The default configuration looks like this:

Limecraft screenshot detail showing the settings of a default ingest process

By default, when new material is uploaded to Limecraft, it will create two proxies in parallel. 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, if you require proxies supporting multi-challen audio, you should change the ingest configuration. Click the green change button, select multitrack and confirm.

Limecraft screenshot detail illustrating how you can enable multi-track audio proxies by modifying the ingest presets

The updated ingest configuration now looks like this:

Limecraft screenshot detail illustrating updated ingest settings to enable proxies supporting multi-channel audio

When new material is now ingested, Limecraft will:

  • first create a mezzanine proxy from the material. This is similar to a web proxy, but including all audio channels (no down mixing). The next transcode job will wait for this to finish.

  • Once the mezzanine proxy has been created, Limecraft will create a dynamic proxy using the former. The dynamic proxy is using Dynamic Adaptive Bitrate encoding suitable for Dynamic Adaptive Streaming over Http ("DASH")which can be played out in the Limecraft player, thereby supporting switching between the different channel layouts.

Note: when sending material from Limecraft Edge to Limecraft 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.

Playing out Multi-channel Audio

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: