FCC Captions Requirements for FAST Channels

Closed captions are required for FAST channels. Roku, Fire TV, and most major TV platforms enforce caption requirements at submission time. The FCC sets the underlying regulatory requirement; TV platforms enforce it technically.

This guide explains what you need, what format, and how to get captions on your content.

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The FCC requirement

The FCC requires closed captions on video programming distributed to US viewers if that programming was previously shown on broadcast or cable TV with captions.

For FAST channels, this means:

• Content previously aired on TV: Must carry captions. If you're licensing content that aired on broadcast/cable, the captions are almost certainly already attached to the master file.
• Original online video content: Generally not subject to the same FCC mandate if it was never aired on TV first. However — and this is critical — TV platforms require captions regardless of FCC mandate status.

The practical rule: any content you intend to distribute on Roku or Fire TV needs closed captions. Whether or not the FCC technically requires it, the platform does.

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Caption formats: what they are and which to use

CEA-608 (analog captions)

The original broadcast caption standard. Embedded in the video file's line 21 data. Supports a limited character set, basic formatting (color, position), and two simultaneous caption channels (CC1, CC2 for primary/secondary language).

If you have older content from broadcast TV, it likely has CEA-608 captions already embedded.

CEA-708 (digital captions)

The modern digital caption standard for broadcast television, DTV, and satellite. Supports more styling (font, size, background), more languages, and is required for HD content by FCC rules.

CEA-708 captions are embedded as a stream within the video file (in the H.264/H.265 SEI layer for MP4 files, or as a caption stream in MPEG-TS).

For FAST channels on TV platforms: CEA-708 is required. Roku and Fire TV specifically require CEA-708 for HD content. If you have CEA-608 only, some platforms accept it for SD content but CEA-708 is always preferable.

WebVTT (web captions)

A text-based caption format (.vtt files) used primarily for web video. Supported by HLS as a separate text track alongside the video stream.

WebVTT is simpler to create and edit than CEA-708 — it's a plain text file — but CEA-608/708 embedded in the media is required for TV platform certification.

SRT (SubRip Text)

Another plain text caption format. Not directly supported in HLS streams but commonly used as a source format for converting to other formats.

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How to add captions to your content

Option 1: Auto-generate captions (recommended for most operators)

Use an AI transcription service to generate captions automatically:

• Amazon Transcribe — Good accuracy, supports multiple languages, output in SRT/VTT
• AssemblyAI — Very high accuracy, supports speaker diarization
• Whisper (OpenAI, open source) — Excellent accuracy, runs locally, free
• Rev.com — Human captions, 99%+ accuracy, $1.99/minute for English; AI captions available at $0.25/minute (pricing current as of May 2026; check rev.com for latest rates)

Vidiyo integrates automatic captioning during transcoding. After uploading content, you can enable caption generation in the content settings — Vidiyo will generate WebVTT captions automatically.

Option 2: Embed captions in your source files

If you're generating captions externally and want them permanently embedded in the video file:

From SRT to CEA-708 using ffmpeg:

ffmpeg -i input.mp4 -i input.srt \
  -c:v copy -c:a copy \
  -c:s mov_text \
  -metadata:s:s:0 language=eng \
  output.mp4

Note: mov_text is MP4 compatible but creates a separate text track, not CEA-708. For proper CEA-708 embedding in a broadcast-compatible MPEG-TS container, you need specialized tools:

• CaptionConverter (paid) — Converts SRT → CEA-608/708 and embeds
• MacCaption (Telestream, paid) — Professional broadcast caption tooling
• Subtitle Edit (free) — Converts between many subtitle formats

Option 3: Deliver captions as HLS text tracks

For modern HLS delivery, you can deliver captions as a separate .vtt file referenced from the HLS manifest:

#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,URI="captions_en.m3u8",LANGUAGE="en"

Vidiyo supports this automatically when captions are available for a content item. The caption track appears in the player's CC menu.

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Roku's specific caption requirements

Roku requires:

• Closed captions must be present for all content on their platform
• CEA-608 or CEA-708 for linear/FAST channels
• Content in English must have English captions
• Caption styling must be user-controllable (the platform provides this at the OS level)

When submitting a branded Roku channel for certification, caption compliance is a common rejection reason. Roku's checklist specifically calls out:

1. All video content includes captions
2. Captions are in the correct format for the content type
3. Captions display correctly without truncation or overlap
4. Caption timing is accurate (within 2 seconds of audio)

Fire TV caption requirements

Amazon Fire TV is slightly more lenient in certification but still requires captions for all content. The platform supports:

• CEA-608/708 for linear streams
• SideCarCaptions (external VTT) for VOD
• IMSC (TTML) for some content types

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Caption quality

Technically valid captions can still be bad. Common quality issues:

Timing. Captions that are consistently early or late are frustrating. Target ±0.5 second accuracy; ±1 second is acceptable; anything beyond 2 seconds is a compliance issue.

Accuracy. Auto-generated captions from AI services typically hit 90-95% word accuracy on clear English speech. For content with accents, domain-specific vocabulary, or poor audio, accuracy drops. For content where accuracy matters (news, educational), human review or professional captioning is worth the cost.

Speaker identification. For multi-speaker content, caption the speaker's name when there's ambiguity about who is speaking.

Sound effects. For viewers who are deaf or hard of hearing, caption significant non-speech audio: [MUSIC], [APPLAUSE], [DOOR SLAMS].

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Checking your captions

Before submitting to a TV platform, verify:

1. Open your content in a player that supports caption display (VLC, a browser with HTML5 video)
2. Enable captions and watch at least 5 minutes
3. Check timing, accuracy, and formatting
4. Confirm captions appear in English (or your target language)

For FAST channels on Vidiyo, you can preview captions in the content library before publishing.

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What's next

• How to start a Roku channel
• How to start a FAST channel
• Converting a YouTube library to a FAST channel