---
title: Missing Captions Troubleshooting Guide
slug: troubleshooting/missing-captions-troubleshooting-guide
createdAt: 2026-03-27T17:44:56.782Z
---

Missing captions can occur at several points in the signal chain. The fastest path to resolution is figuring out where captions disappear.

## Step 1. Isolate the Fault Point

Before changing anything, capture and inspect the stream at each stage:

- **Source (encoder output)** → **Zixi input** → **Zixi output** → **Decoder/IRD**

Use a TS analyzer (Wireshark, a hardware analyzer, or VLC with stream info) to check whether captions are present at each stage. The point where they vanish is the fault point.

## Step 2. Check the Source Encoder

If captions are absent from the start of the chain this is likely an issue at the encoder.

**Things to check:**

- Is closed caption passthrough enabled? This is a common miss after a firmware update, reconfiguration, or factory reset.
- Is the encoder transcoding the video? Transcoding pipelines frequently strip CEA-608/708 data unless CC passthrough is configured.
- Verify the source material is actually captioned. Live sports and news feeds typically are, but the caption insertion feed (e.g. a separate caption encoder) may have its own failure.
- Are there frame drops in the encoder logs? CEA-608 data rides per-frame inside the video elementary stream dropped frames mean dropped caption bytes.

**Fix:** Enable CC passthrough in the encoder settings. If transcoding, ensure the transcoder is configured to re-encode or pass through caption data. Refer to your encoder vendor's documentation for specific information.

## Step 3. Check the Zixi Path

If captions are present at the Zixi input but missing at the output, something in the broadcaster/ZEC processing chain is removing them or an error is occurring.

**What to check:**

- Is any transcoding or remuxing being applied inside Zixi Broadcaster? This may be inadvertently stripping out the caption data.
- On failover sources, did a source switch occur recently? The backup source may not be configured identically to the primary. Check that the failover source encoder has the same CC settings.
- Review ZEN Master source/channel/target and Broadcaster logs around the time captions went missing. Look for source switch events, errors, or unexpected restarts.

## Step 4. Check the Decoder / IRD

If captions are present in the Zixi output but still not displaying at the endpoint:

**What to check:**

- Is the decoder configured to decode the correct caption service?
  - CEA-608: CC1 or CC3 (field 1/field 2)
  - CEA-708: Service 1 (most common default)
- Has the decoder been recently rebooted or reconfigured? Caption decode settings can reset to defaults.
- Does the playout or monitoring system have a caption rendering/overlay setting that may be disabled?

## Troubleshooting Decision Tree

Captions reported missing 

ZEN Master alert raised? → YES → Event Notification Profile has caption monitoring enabled — trace chain below to find fault point 

Captions absent from source TS? → YES → Encoder issue (Step 2) 

Captions present at Zixi input, missing at Zixi output? → YES → Distribution/processing issue (Step 3) 

Captions in Zixi output, not displaying at endpoint? → YES → Decoder / IRD issue (Step 4) 

A clear fault point found?  → NO → Capture TS at input and output and escalate to Zixi Support

## ZEN Master Event Notification Alerts

If you're using Zixi ZEN Master, it can be configured to actively alert on missing captions. If your **Event Notification Profile** has caption monitoring enabled, ZEN Master will raise an error any time captions are not detected in the stream.

- A ZEN Master caption alert is a reliable signal that captions are absent, but it isn't able to tell you *why.* Use Steps 1–4 above to find the fault point.
- If captions are intentionally not present on a channel (e.g. a non-captioned feed), disable the caption check in the Event Notification Profile for that channel to avoid false alarms.
- Check your Event Notification Profile settings in ZEN Master under *Settings → Event Notifications *to confirm which event types are active and which channels they apply to.

## Escalation

If captions are confirmed present in the Zixi output stream but a downstream device is still not displaying them, provide the following to support:

- TS capture at the Zixi output (.ts or .pcap)
- Encoder and Zixi Broadcaster logs covering the affected time window
- Decoder model and firmware version
- Whether the issue is constant or tied to specific events (e.g., source switches, time of day)