Accessible Audio and Video

For an audio-only recording, prepare a transcript containing the speech and relevant non-speech information. W3C's explanation of WCAG 1.2.1 describes an equivalent alternative for prerecorded audio-only content, subject to the criterion's stated exception for a clearly labeled media alternative for text.

For video with meaningful audio, prepare synchronized captions. W3C's explanation of WCAG 1.2.2 includes speaker identification and important sounds alongside dialogue. Dialogue-only translated subtitles may leave out that information. The words “captions” and “subtitles” also vary by region, so specify the content you need when arranging the work.

Review the visual information too. A speaker may point to a chart, demonstrate a step or display a name without saying it. Captions reproduce audio information; they do not automatically explain those images. W3C's description guidance addresses that separate task. A descriptive transcript combines relevant visual descriptions with the speech and sound information in a readable document.

A descriptive transcript is not a universal replacement for audio description. W3C lists audio description for prerecorded synchronized video under WCAG 1.2.5 at Level AA; assess the applicable criterion and the information already conveyed by the soundtrack.

Ask the intended audience how they will use the recording. Someone may need text while watching, a separate document they can navigate, description of the images, or another access arrangement. This is a practical planning question rather than a reason to assume one format works for everyone.

Scroll horizontally to inspect the diagram.

Source: W3C WAI media, transcript and description guidance. Conceptual relationships; the routes are not interchangeable or a measured complete-access score.

Keep the original recording and work on a clearly named copy. Note which passages are difficult and what you need to produce: an interview transcript, a captioned training recording or a reviewed presentation copy, for example.

If you process the audio, compare difficult words with the reference recording. Judge whether the passage is easier to understand and whether speech detail has changed. Reducing a distracting sound does not justify filling an uncertain gap in the text. Keep a note of uncertainty for the person checking the transcription.

For casework, follow the required transcription and evidence-handling instructions. W3C's transcription guidance explicitly distinguishes a verbatim legal deposition from ordinary web content where some non-substantive speech may be omitted. Do not silently turn a verbatim record into an edited reading copy.

If speech remains hard to follow, our guide to unclear speech after noise reduction explains why further cleanup may have limited value. Keep the text review separate from any restoration decision.

Start a caption draft by typing the audible speech and relevant sounds yourself, or by using automatic speech-to-text as a starting point. If a script exists, check it against what was actually recorded. Choose a workflow that lets you correct the text and set the times when each caption appears and disappears.

Treat automatic transcription as a draft. W3C's transcription guidance warns that errors can change meaning, including when a small word is missed. Review the text while listening to the corresponding passage, rather than correcting it from what a sentence seems likely to say.

Check names, numbers, negatives and changes of speaker carefully. Use consistent speaker labels supported by the recording or reliable supplied context. Do not guess a person's identity from a voice. If the words cannot be understood, use a clear uncertainty label such as “[unintelligible]” and retain a useful time reference for review.

Include sounds that matter to understanding the content: a relevant alarm, an off-screen response or laughter that changes the meaning of an exchange. Avoid transcribing every background sound simply because it exists. The purpose is to carry useful information to someone who cannot hear it.

For captions, break the text at sensible phrases and check that it can be read while following the video. W3C gives one or two lines and short line lengths as common captioning practices. The final presentation also depends on the content, language, player and audience; do not force an arbitrary line break that separates a name or changes the meaning.

Caption timing belongs to the version people will watch. If an editor removes a passage after the captions are prepared, recheck every affected cue. Check the beginning, middle and end as well as edited transitions.

The Library of Congress describes SubRip, or SRT, as a separate text file containing numbered caption blocks, start and end timestamps, and caption text. Its usual timestamp notation uses a comma before milliseconds. An SRT file contains no audio or video.

Here is a small example from the synthetic timing demonstration:

1
00:00:00,800 --> 00:00:01,400
[short tone]

2
00:00:03,000 --> 00:00:03,900
[two short tones]

The example uses deliberately generated tones with known timing. It contains no customer recording, uncertain speech or restoration comparison. It shows how a caption cue relates to an event; it cannot demonstrate transcription accuracy on a difficult recording.

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Source: the generated tone file and its matching SRT/WebVTT cues. Known synthetic intervals, in seconds; not a recording-restoration result.

Open the synthetic player example and transcript

Choose a caption delivery format for the viewing copy

Confirm the format your destination accepts. MDN documents WebVTT, with the `.vtt` extension, for a browser's HTML text track. Uploading an SRT file to a platform and attaching a WebVTT track to an HTML player are different delivery routes. Renaming a file extension alone does not convert its contents.

A sidecar caption file is a separate timed text file paired with the media. Choose a format the actual player or hosting platform supports, attach the matching file and check that viewers can select the intended track. Merely keeping the caption file beside a video does not prove the destination will display it. If the destination cannot display a separate track, a separately exported viewing copy can have captions burned into the picture, where they remain visible and cannot be switched off. Keep the original and editable caption file; check text size, placement and timing in that exported copy.

Open the actual exported media in the destination player. Confirm that the intended caption language appears, the track can be selected and its text follows the recording. Look for missed cues, timing drift, unreadable line breaks and captions covering important information in the image.

Check the controls with a keyboard: reach the player, start and pause playback, find the available caption control and continue past the player. A visible focus indicator and clear control labels matter. W3C's player guidance also calls out sufficient contrast and operation when the page is enlarged. Test the published placement on a narrow screen and with increased text or page size, rather than relying only on the caption editor's preview.

Put the transcript or a clearly labeled link near the media. W3C recommends making transcripts easy to find and usually placing them on the same page. A descriptive transcript needs the visual information too; simply removing timestamps from a caption file may leave out a displayed title, a chart or a silent action.

If you change the media after review, check the matching caption and transcript versions again. Keep their filenames and version notes together so a later upload does not pair new video with old text.

Scroll horizontally to inspect the diagram.

Source: W3C transcription/transcript/player guidance and DCMP caption-quality principles. Editorial workflow derived from accuracy and synchronization requirements.

Explain which passages are difficult and how the recording will be used. If you need a transcript, captions, description or a particular delivery format, name that output explicitly and confirm who will prepare and check it. A request for audio restoration does not by itself define those additional tasks.

Media Medic's restoration review can help assess what may improve in a recording. Transcription is an additional paid service; caption and access-format deliverables should be discussed rather than assumed. If the material identifies people or contains restricted information, discuss the actual file-handling arrangements before sharing it.

This guide separates the roles of captions, transcripts, description and player controls using W3C's published guidance, then cross-checks caption-file delivery against the Library of Congress's SRT description and MDN's HTML track documentation. It applies those distinctions to an existing-recording workflow.

The accompanying example was created from known tone intervals so caption timing can be inspected without suggesting that words were recovered from an unclear recording. It is a format demonstration, not a usability study, a restoration result or a test of every browser and platform. The workflow does not establish that a particular recording meets every audience need or any legal requirement.

Start with the information people need. Preserve the reference recording, check the words and meaningful sounds, match captions to the final media, and offer an easy-to-find transcript. Review the actual player and audience needs before calling the output ready.