I/O, Clocking, and Reference

Input and Output Routing

Connect your SDI, AES-3, and/or AES67 sources to the rear panel of the LA-5291 as required for your installation.

The LA-5291 can access any of the eight audio pairs carried on its incoming HD- or SD-SDI streams. Inputs and outputs for five stereo pairs via AES-3 are also provided.

Note - Although the hardware is present for two independent SDI I/O paths, only the first SDI I/O is active at this time. The second path will be enabled in a future firmware update.

Any visible and accessible AES67 networked audio source can be input into LA-5291 for decoding, transcoding, or encoding, then returned to the network via AES67, embedded into the SDI output, and/or sent to the AES-3 output.

LA-5291 supports taking an input signal for decoding, transcoding, or encoding from one source type and sending the resulting audio or bitstream to another output type.

Initial I/O Setup

Log into the LA-5291 and click on the I/O menu (1A). Choose between SDI/AES-3/MADI or AES67 inputs and outputs in the Workflow menu (1B).

Signal Routing

Routing a signal into the LA-5291 is a two-step process.

The first step is creating an input group from the available physical hardware inputs (2A). The second step is routing the audio from these inputs into the transcoder input (2B).

Routing a signal to the output is a similar two-step process.

The first step is creating an output group from the available physical hardware outputs (2D). The second step is routing the audio from the transcoder output (2C) to the physical outputs.

Creating an Input Group

Click on your first audio input source (3A) to highlight it, then right click and select “Create Input Group.” You may enter a custom name for this source in the Label field (3C) and customize the color (3B) of the graphical routing lines.

Click the Save button (3D) to save the configuration or the Cancel button (3E) if you need to start over without saving your configuration.

Routing a Signal to the Transcoder Input

After saving the input group, it is necessary to first set the priority of the input source by dragging the input audio lines (4A) and then clicking when the desired priority level is highlighted (4B). The LA-5291 will look for a signal first on the inputs connected to Priority 1. If no signal is present, it will look to subsequent priorities in order.

Important - Priorities must be configured so that encoded sources are a higher priority than PCM (non-coded) sources.Important

Next, choose the input signal type for this input group (PCM, Dolby E, or Dolby ED2) from the Type dropdown menu (5A).

To edit or delete a group, highlight then right click on the colored Edit rectangle (6A).

Creating an Output Group

The steps for creating an output group are identical to creating an input group, but with the Outputs menu.

Routing Transcoded Audio to the Physical Output

Once the first output group has been created and saved, drag the output audio lines to connect the physical outputs to the output of the transcoder, then click to save.

Latency and Delays

Latency through the LA-5291 varies depending on which inputs and outputs are used and whether or not SRCs are enabled. In any case, it will be necessary to compensate for any latency incurred by the transcoding process. Please see the Specifications section for latency measurements for the current software version.

To compensate for the encoder’s latency and avoid lip-sync issues, an SDI video delay is provided in the Delays sub-menu of the I/O menu (5-7A). Click on the millisecond and/or microsecond fields in the Video Delay section (5-7B) and type in the required value. If the output needs to be delayed by an even frame (the value of which will vary depending on frame rate), simply enter that number.

Note - Entering an even frame value will result in a situation where it is necessary to add additional audio delay to the AES67 and AES-3 outputs so that they match the timing of the SDI output signal. This can be accomplished by setting the Audio Delay (5C) to a value equal to the difference between a full frame and the latency of the unit.

Sample Rate Converters

Sample rate converters (SRCs) are provided on each SDI input pair, each SDI output pair of the first SDI output, and each AES-3 input pair. The AES-3 output is always synced to the active reference clock. There are no SRCs in the AES67 path.

The SRCs can be enabled and disabled per pair by first highlighting then clicking on the appropriate input or output pair, and then selecting Channel Settings (8A).

Important! Only PCM audio can be passed through a Sample Rate Converter. Coded audio bitstreams including Dolby Digital Plus, Dolby Digital Plus JOC, Dolby ED2, and Dolby E cannot be passed through an SRC without corrupting the data stream.

Clock Reference

Because the LA-5291 offers very flexible signal routing and supports multiple input and output formats, having a firm grasp of the clock sync (reference) requirements is critical.

Clock Reference Requirements

Sample Rate Converters (SRCs) are provided on both SDI inputs, the SDI 1 output, and the AES-3 input. The AES-3 output is always synced to the active reference clock. There are no SRCs in the AES67 path.

Reference clock source options include:

• Internal 48kHz

• SDI Input

• AES-3 InputMADI Input (when optional MADI card is present)

• PTP (AES67)

When all input sources are SDI and the output of the transcoder is routed to the embedded SDI output, the reference signal present on the SDI input must be used.

When using AES-3 I/O, the LA-5291 can be referenced to either the AES-3 clock (using the SRCs in the SDI path) or to the SDI clock (using the SRCs in the AES-3 path.

When using an AES-3 source without an accompanying reference, the LA-5921’s 48kHz internal clock can be used as the system reference if necessary, providing the SRC on the AES-3 input is enabled.

Whenever AES67 audio is used either on the input, the output, or both, the LA-5291 must be slaved to an externally-generated PTP clock as it cannot generate its own PTP reference.

Note - The LA-5291 is set to operate in slave mode by default. There are controls in the Sync/ QoS sub-menu of the System menu to change this should the ability to operate as a clock master be introduced in future software versions, but only Slave Only mode is currently supported.

Setting Clock Reference

Click on the Clock menu (9A). Use the dropdown menus to choose a Primary Reference Clock and a Secondary Reference Clock (9C) and, if needed, a VRef clock source (9E).

The status of the selected Primary and Secondary Reference Clocks is shown to the right of the dropdown menu (9D). The absence or presence of a signal for each input type along with the format, resolution and frame rate for incoming SDI signals is shown in the Input Status section (9B).

GPI/O

The LA-5291 offers five GPI and five GPO functions through its rear panel DB-15 connector, activated by a momentary contact closure.

GPI/O Pinout

GPI/O Functions

GPI functions (11A) include:

• None

• Reboot/Reset Unit

• Hardware (Relay) Bypass

GPO functions (11D) include:

• None

• GPI Passthrough

• Power Supply 1 up

• Power Supply 2 up

• Power Supply 1 down

• Power Supply 2 down

• Unit resetting

• Unit rebooting

• Unit powering down

• Unit above temperature

• Unit bypass (relay bypass) active

• Change in reference

• Primary reference clock is lost

• Secondary reference is lost

• Primary reference clock is active

• Secondary reference is active

• Internal reference is active

The State Indicator (11B) for each function will light for the duration of the closure on GPIs. For GPOs, it will light for the duration of the active event.

At this time, there are no user-defined Parameters (11C) associated with any GPI or GPO. Should functions with such parameters be included in future software releases, they will appear in a dropdown menu.