SDI Audio Embedder

1 Preface

With the Audio Embedder feature the tracking data stream can be embedded into an audio channel of the incoming SDI video signal. The tracking engine outputs the SDI video with embedded tracking data which can then be fed into a graphics engine. The Pixotope Graphics engine can de-embed the tracking data in the Director. For other graphics engine vendors a Standalone SDI Tracking Data De-Embedder software product, running in Windows, is available.

This feature makes the recording and playback of tracking data very easy. Any device that can record an SDI video feed with uncompressed audio can record the tracking engine output, meaning recording the video together with the matching camera tracking data.

The following requirements are needed:

• A Blackmagic video card with SDI input and output in the tracking engine

• Audio compression must never be applied to the tracking data embedded in the audio channel. It turns the tracking data unusable and can not be reversed

• Only for Pixotope Fly: A video card with two SDI inputs and one output

2 Setup

2.1 License

For using this feature a license addon is needed. Open the License Manager and log in to your user account. Either check out a camera tracking license which includes the SDI Embedder addon or select the SDI Embedder from the Available Addons field. If you need to select a camera tracking package and an addon, use the Ctrl key to select both and then click Checkout.

2.2 Chief

1. Start the Chief and click on the Setup button

2. If there is no Audio embedder option in the Setup menu, update the Chief package to the newest version

3. Activate the Audio embedder option and click Save + Quit/Restart

2.3 Video In and Out

1. Connect the SDI cables for video In and Out to the desired spigots and route the video of the tracked camera to the input spigot.

For Pixotope Fly both Worker and Chief need to receive the SDI video. For this reason the video needs to be fed into two separate spigots of the video card.

2. Click on the Linux Menu on the left side of the task bar

3. Type in “blackmagic” and open the Blackmagic Desktop Video Setup

4. Configure all Connector settings to In or Out

3 Operation

3.1 Camera tab

Device, Connector and Video Mode refer to the incoming video. If these settings are not matching the video routed to the tracking engines input, no video will be shown in the Chief Video window.

Pixel Format defines the depth of color of the Chief video that the tracking engine works with and outputs. When not using the audio embedding this can be set to 8 Bit to save processing time. when using the audio embedder, in most cases the video coming from from the tracking engine needs to be in the highest possible quality, meaning 10 Bit. However, if no device which receives the SDI video from the tracking engine needs more than 8 Bit depth of color, this setting can be set to 8 Bit.

Audio Channels defines the number of audio channels in the SDI signal that the tracking engine will pass through. The tracking data will be embedded into one audio channel meaning that one more audio channel will be used compared to when not using audio embedding. The SDI standard gives only the options of selecting 2, 8, 16 or 32, so this value has to be set to a number high enough for the amount of channels used for audio data plus one more channel for the tracking data. For example in case two audio channels are occupied with audio data, that means a third audio channel will be needed for the embedded tracking data. In such a case it would need to be set to 8. The channel to contain the tracking data will be defined in the Audio Embedder tab.

Bits per Sample is similar to Pixel Format. Set it to 32 for the tracking engine to output the video with the highest possible quality.

3.2 Output tab

Device, Connector and Level in this tab refer to the outgoing video.

3.3 Audio Embedder tab

With the drop down button at the top of this tab the format of the tracking data is defined in order to match the graphics engine being used.

Channel defines in which of the audio channels the tracking data will be embedded. The number of audio channels must be defined first in the Camera tab and the Chief restarted. A channel must be chosen that is not used for any audio data.

Offset offsets the position of the tracking data inside the audio channel by bits. This can be needed in case any of the devices used in the signal pipeline corrupt the first bits of the signal. In case no tracking data are recognized by the de-embedder even though embedded, try an offset value between 20 and 800. This setting does not change anything for the de-embedder.

Dump prints information about the embedding in the system log (see also next chapter). It prints the amount of audio packet samples and bytes for the tracking data. Every five seconds it additionally prints one line containing 42 bytes for the meta data (Illustration 7).

3.4 Send Delay

The Send Delay needs to be controlled after the Audio Embedding has been set up.

1. Activate the Dump in the Audio Embedder tab

2. Go to the Delay tab

3. Set the Send Delay to a value between 1 and 19 where the Audio embedder Dump appears completely regular as shown in Illustration 7. Keep in mind that every five seconds one line for the 42 bytes of metadata will be printed too

4 De-Embedder

The De-Embedder for the Pixotope Graphics engine as well as the standalone De-Embedder software will be available from Pixotope Graphics release 24.1, expected end of May 2024.

If you want to use the De-Embedder before 24.1 is released, please contact support@pixotope.com.