Using the Multi-Track Audio Config Interface

You can use the Audio Config tab to configure multiple audio tracks, and the channel layout for each within MPEG Transport Streams. This is only available for MediaConnect and SRT inputs. This guide explains the components of the interface, and explains some common use cases.

Interface Overview

1. Mixes: The central feature is a grid where each row represents an input channel and each column represents an output channel. The input and output channels are grouped into tracks by their headers. This is where you will define the layout and routing from inputs to outputs. You can define multiple mixes with different sets of commentary teams each with it's own layout. Each mix can each be sent separately to multiple downstream destination from the Outputs tab. Each commentary team can be assigned to only 1 mix.

2. Input Track Layout: On the left side of the grid, you'll see your input tracks labeled as TK 1, TK 2, etc. These are the tracks coming from your commentary teams or clean input transport stream. The number of rows below each header defines the number of audio channels in that track. It is important that this track layout matches the input layout you expect in the Transport Stream Spalk will receive live, otherwise you may encounter errors.

3. Output Track Layout: Along the top, you will see an identical track layout to the input, this is due to the way Spalk's MPEG-TS multiplexer works, requiring you to replace tracks that already exist in the input Transport Stream.

4. Audio Routing Matrix: This is the area with the checkboxes inside each Mix. It allows you to direct input tracks to output channels by checking the corresponding boxes. If you wish an input track to be present in the output track, the checkbox where they intersect must be clicked. For example if you wish Channel 1 on the input to be present on Channel 1 of the output, you should check the top-left check box.

5. Latency Field: At the bottom of a mix, you can set its latency in milliseconds. This is the delay applied to the stream to ensure the commentary audio has time to be synchronised and added. See How to choose latency below for more information.

6. Preset Buttons: At the top of the tab, there are buttons to group, split, and reset config to default, affecting how tracks are mixed and managed. This allows you to quickly configure large numbers of commentary teams.

7. Channel Count: At the top of the tab you can use the + and - buttons to increase and decrease the number of channels you expect in your clean audio input transport stream.

Example: Mixing Two Languages into a Single SRT Output

1. Start with Two Mixes:
 - Assume you have two commentary teams in two languages – English and Bengali – each on separate mixes initially.
 - Assume we also have International Sound (clean game sound without commentary) present on the clean input audio track 1 and 2.

2. Combine the Commentary Teams:
- Drag the Bengali commentary team from its separate mix (Mix 2) and drop it onto Mix 1 with the English commentary team.
- Delete the now-empty Mix 2.

3. Configure the Mix Matrix:
- Ensure that the English commentary is on Track 1, channels one and two.
- Place the Bengali commentary on Track 2, channels three and four.
- Adjust the mix matrix checkboxes to ensure that the correct input tracks are going to the correct output channels. The international sound should be on Track 1 (channels one and two) and the commentaries should be correctly assigned to their tracks. The interface will resemble the below

4. Save the Configuration:
- Click 'Submit' to save the configuration. If the stream is live, reset the media workflows to apply these settings.

5. Set the Output:
- In the outputs tab, you will see that both commentary teams are grouped in the same gray box, indicating they are on the same mix.
- Input the SRT output URL or destination. This is where your single mixed stream will be sent.

6. Final Checks and Submission:
- Schedule the output if necessary by setting a time for the stream to go live.
- Perform a final check to ensure the mix levels are correct and the teams are correctly assigned.
- Submit the final output. If you're live, make sure to reset the media workflows so the changes take effect.

Example: Sending Full-Mix and a Isolated Commentary Tracks in the same Transport Stream

Sometimes it is useful to send both a full mix (commentary + international sound) and an isolated track, for further downstream mixing and archiving purposes. Here is how to lay out your audio mix to achieve this.

1. Select Your Teams: Identify the commentary team you wish to mix. In this example we have a single French commentary we want to send in this style. We will assign a Mix on channels 3+4, and isolated commentary on channels 5+6.

2. Assign Teams to mix:
- By default the team will be in it's own mix, if this is not the case drag the team to a new clean mix.

3. Configure Mixed Output Channels:
- In the mix matrix, ensure that the selected output channels for the full mix contain both international sound, and the commentary input channels.

4. Configure Solo Output Channels:
- In the mix matrix, further ensure that the selected solo output channels are mapping just the team's input channels.

5. Check and Save:

 - Review the matrix to ensure all settings are correct. The boxes should be checked in such a way that the audio from both tracks is routed to the same output channel. Click 'Submit' to save the mix. It should resemble the screenshot below.

 

How to choose latency

At the bottom of a mix, you can set its latency in milliseconds. The latency is the amount of delay applied to the stream to ensure the commentary audio has time to be synchronised and added. If the the mix has a commentator whose network is slow and the latency is too low, we will be unable to synchronise them as their audio arrives too late, and there will be a delay on the output.

We recommend as follows:

- If the mix contains a commentator whose network is slow, we recommend using a value greater than 2000ms.

- If the mix contains only commentators with reliable network connections, we recommend setting this to 'Auto' when there is one commentary team, and 2000ms when there are multiple commentary teams.

 

Important Notes

- Resetting: If you reset a commentary team within a mix, it will impact all commentary teams within that mix because they share the same output.
- Independent Levels: Each commentary team's audio levels can be independently adjusted without affecting the other team.
- Save Often: Regularly click 'Submit' to ensure changes to your configuration are not lost.
- Adding Tracks: If you wish to add audio tracks to the event, ensure that the ingest has a minimum of 500kbps null packets per track you want to add.
- Support: If you have any questions, do not hesitate to contact support for assistance.

By following these steps, you should be able to successfully combine multiple commentaries into a single MPEG-TS using the multi-track SRT interface.