How to configure CDI

Owned by Ramya Raman (Unlicensed)
Last updated: Oct 20, 2021
2 min read

Content Distribution Internetworking (CDI) is supported only on cloud instances (AWS) along with EFA (Elastic Fabric Adapter) enabled. CDI is similar to 2110 which enables the transfer of uncompressed content with low latency. Unlike 2110, CDI is unicast and sends multiplex data, i.e audio and video on the same stream. Metadata in CDI is transferred as in 2110-40.

CDI consists of Recieve (Rx) and Sender (Tx) configurations.

Tx Configuration:

For Tx configuration follow the below steps.

  1. Navigate to Outputs → Configuration. Click on edit an existing encoder or add a new encoder and navigate to Auxillary Streams.

2. In the CDI Publish Point section, input the Url, Network, and check the Enabled checkbox to enable CDI Tx configuration. Since CDI is a push protocol, the URL should include IP+PORT. For example, cdi://1.2.3.4:3000

By default, the transmitted stream, is a single stream, holding the video under “stream_id=1” and audio under “stream_id=2”. the stream ids can be defined by a more sophisticated URL: cdi://11.11.1.1:3000?video=20&audio=2

If only the video or the audio is defined, the other element is ignored.

3. For Encoder Configuration please refer to Encoder Configuration. Additionally, take into consideration the below parameter for interlaced content transfer on CDI.

Interlaced content handling on Tx:

There are multiple ways to send interlaced content on CDI:

  1. PsF: single buffer, full resolution, interleaved lines. Selecting one of the progressive SDI modes - 3/6/12 GB will produce PsF.

  2. Two Fields per buffer: first is the top, second is the bottom, sent on the same buffer. Selecting 1.5G SDI mode - will produce fielded stream - 2 per buffer.

  3. Single Field per buffer: buffer is effectively half res on the height. Currently not supported on the config - CDI doesn’t support this directly.

Configuration on the encoder - in all three cases, the “interlaced” checkbox should be checked.

Rx config:

For a detailed description of adding CDI sources please refer to CDI.

Configuration is similar to 2110: A receiver should be configured for video and each of the audio/metadata.

When configuring the “CDI/Audio” component: The receiving port can be the same and the video or empty (same), and the audio will be demuxed from the same muxed stream.

If a different port is defined: An additional receiver will be started.

“StreamId” defines the selected stream id from the muxed content. If left empty the first stream with the relevant content will be selected instantaneously (or 2nd/3rd … depending on the configuration). The same logic applies to metadata.