AJA FS4: timecode during conversion and AES audio from multiple HD feeds

FS4 and timecode preservation

Timecode Xlator is documented from firmware v3.0 onward. Record the unit's version under CONFIG > 13 Software Version, p. 59; the PDF edition does not establish the installed firmware. The FS4 v3.1r1 manual (published September 3, 2026) describes what this signal path supports.

For an EVS setup, identify what XTGO generates and what the specific Epsio version expects before testing. This guide covers AJA's documented handling of ATC packets. It does not extend that support to every signal called LTC or VITC, or provide EVS settings without the applicable manual.

Check ATC before and after conversion

Under ANC > 6 Timecode Xlator, p. 70, On allows LTC, VITC1 and VITC2 ATC packets to pass or be translated to the configured Output Format during conversion. Off is the factory default: it passes ATC without conversion and removes it when converting. The same page lists exceptions; enabling the control does not guarantee every format or destination.

In Four Channel Mode, ANC applies to the selected VID1–VID4, p. 67. Check which processor carries the signal. Review its input and Output Format as well as the system Output Frame Rate and Genlock Source; the general setup steps, pp. 43–44 separate those settings. Follow Input follows the input and does not by itself force 1080i59.94.

For an off-air test, save the initial state and check that the source supplies the required ATC before the FS4. Select the intended path and conversion, check Timecode Xlator on that processor, and compare the data at its output. Use a tool that reads the packet and also check the destination's reading. Recording a number visible in the picture does not establish that it traveled as ATC.

If the data is missing before the FS4, check the source. If it is present at the input but missing at the output, check the version, processor, format and Timecode Xlator against the manual. If it is present at both points but the destination cannot interpret it, record the packet type, continuity and receiver requirement before attributing the problem to the converter. Delay, continuity and EVS compatibility have not been measured for your setup.

Four independent HD feeds: choose the mode before configuring

The FS4 v3.1r1 manual, pp. 10–12 distinguishes Four Channel Mode, with four independent HD/SD processors, from Single Channel Mode, with one processor capable of 4K/UltraHD. Connectors carrying one UHD signal do not represent four independent sources. Frame-rate conversion also has limits by family; record 59.94, 50 or 60 precisely.

Under CONFIG > 2 FS4 Mode, p. 43, HD/SD selects Four Channel Mode and 4K/UHD selects Single Channel Mode. Changing modes requires a reboot. Prepare this off air and save the configuration first: pages 46–47 explain that settings and presets are separate for each mode, and a Four Channel Mode preset affects all four channels.

With Four Channel Mode selected, identify the input, VID and output connector for each path. In the documented single-link transport, VID1 feeds SDI Out 1 and SDI Out 5 if the optional SFP is installed. Other transports use connectors differently. Check the signal and format at the receiver before accepting each path; the FS2 OUTPUT menu must not be assumed to apply to the FS4.

Combine audio from four SDI inputs at the AES output

The following map is a proposed test using SDI inputs. If a camera enters through an SFP or another input, select its actual port instead.

The MAP menu, pp. 93–95 routes audio inputs to individual outputs. In the FS4 browser interface, AES > Map, p. 116 shows AES Audio Out. Select Map to choose the source for each channel of that output. Also check AUDIO > 8 Global Audio Output, p. 63: Off enables individual selections; a global source imposes a common route on all outputs. Save its state before changing it.

Test one source at a time with channel identification and controlled monitoring. At the receiver, check where each channel arrives and whether audio from another input is present. The map takes audio from SDI inputs; this does not establish that it automatically follows the video selected for each VID or any output BNC. Check the model's AES/EBU cable and pinout before connecting it; do not use the FS2 analog wiring diagram.

Then verify each pair's timing relationship with its video. TIMING > 1 Maintain A/V Sync, p. 83 links video timing adjustments to audio delay under specific conditions; selecting Map as the VID's audio source disables the function. A mixed AES map does not establish automatic synchronization of four feeds. Delay must be measured in the actual path, with the receiver and transport in use.

Record acceptance for each destination

Complete the blank FS4 worksheet. Record one change per test, the settings needed to restore the initial state, and separate evidence for picture, reference, audio and ATC. Leave the result pending if the test has not been performed.

For the other model's controls, see FS2: format, reference and audio. If the next device is a switcher, see the AV-HS410 guide. The full path for conference screens, recording and streaming helps define the destinations for video processing.

Speech arrives before the picture: measure the audience's signal path

To measure the offset, use a test signal with a visible and audible event that is identifiable and repeatable. Compare both at the destination of interest, using the normal camera, processor, audio and screen or recording path. Record whether sound arrives early or late and which method can measure it. A test recording also needs its own synchronization checked; do not assign a number based on a visual impression.

If speech arrives early, assess audio delay in the relevant branch after measuring. If it arrives late, adding more audio delay makes that offset worse: review the paths and the adjustments supported by the exact equipment. Save the initial values and change one variable per test. To locate where the relationship changes, compare accessible points along the path using the same method.

The FS4 v3.1r1 manual, pp. 92–93 applies DELAY to input audio by channel pair. Under EMBED > DELAY > 1.0 SDI1 Delay, Global uses one value for all eight pairs; Channel Pair recalls each pair's values. Switching between them changes the values applied. Record the mode and values first, then check every output receiving that input.

For any Sony, Ross or Blackmagic equipment, or an audio console, identify the model, version and applicable manual before changing its settings.

Maintain A/V Sync: align first, then follow subsequent changes

TIMING > 1 Maintain A/V Sync, pp. 83–84 establishes a one-way link: a video timing change can change audio delay. Adjusting audio delay does not change video timing. Switching from Off to On does not immediately change the current delay, so toggling On/Off does not compare two offset corrections.

The AJA procedure example, p. 85 routes SDI 1 video and audio to Video 1 and SDI Out 1. It sets up the paths first, then, with Maintain A/V Sync Off, adjusts video timing followed by EMBED SDI 1 Delay to align them. If video timing needs changing afterward, it enables On and adjusts only that timing. If video remains correct but audio synchronization changes, it adjusts only audio delay.

That sequence is the manufacturer's procedure for its example, not a test performed by GLMedia. Before applying it, confirm that the VID audio source is SDI, AES or MADI. Mix Down, Sig Gen, Mute and Map disable the function. In Four Channel Mode, the master VID also matters when audio is shared.

To compare configurations, save each state and record its values. The manual proposes presets for A/B comparisons, but recalling a preset replaces settings and affects all four channels in Four Channel Mode. Prepare that comparison off air and check every affected destination; a preset does not change only one delay value.

One audio source shared by several VIDs: what the master controls

Shared-audio behavior is documented in FS4 v3.1r1, pp. 85–86, figure 36. Of the VIDs taking the same audio source, the lowest-numbered VID is the master. In the example, VID1 and VID2 take AES: changing VID1 timing with Maintain A/V Sync On changes AES Audio Delay, affecting audio on SDI Out 1, SDI Out 2 and the digital AES output. Changing VID2 timing does not change that shared delay.

The note on p. 86 retains the same master even when its Maintain A/V Sync is set to Off. Disabling it does not transfer control to another VID. Directly adjusting AES Audio Delay also affects destinations using that source, as the figure shows; do not treat it as an adjustment for only one screen.

To prepare the test, draw which audio input each VID uses and which outputs receive it. Identify the master from that routing. Save the initial state, verify the function's conditions, and test a timing change on only one VID, off air. Record the delay before and after and reception on every branch, then restore the agreed state.

If destinations need different adjustments, a shared source does not provide independent output delays. Measure each path and check which control the exact equipment on that branch supports before reorganizing the system. AJA's figure explains an internal FS4 interaction; it does not guarantee lip sync on LED screens, TVs or streams.

Use the FS4 audio synchronization worksheet, which is blank, to record the shared source, master and effects at each destination. When planning video processing, add that information to the screen, recording and streaming diagram.