Convert M4A to captions

Create accessible closed captions from your M4A audio. Convert Apple audio content to professional captions meeting accessibility standards.

ADA compliant
5-min turnaround
Accessible
Audio
Video
DOCX
SRT/VTT
PDF
53+ Languages
About This Format

Understanding M4A files

What is a M4A file?

Apple's audio format with superior quality at small sizes

An M4A audio file is a lossless audio format (and encoding algorithm) created by Apple and utilized on a variety of Apple products (including iPod, iPhone, iPad, iTunes, and Quicktime products). The m4a codec has been open-sourced so it is quite popular. M4A files are usually encoded with Advanced Audio Coding (AAC) which was originally designed to be the successor to MP3.
Both MP3 and M4A files are used for audio-only files, and are both unprotected (free from DRM features). Protected files will have a *.m4p file extension. AAC or M4A files do have better audio quality when compared to MP3 files when encoded at the same bitrate due to some of the codec’s improvements such as compression based on perception and a smaller block size for changing audio sounds and signals.

Common Uses

  • iTunes music library
  • Apple podcasts
  • Audiobook distribution
  • Voice memos on iPhone

Audio Quality

Better quality than MP3 at same file size

Transcription Tips for M4A

  • Excellent for transcription - designed for clear audio
  • AAC encoding provides better speech clarity than MP3
  • iPhone voice memos use M4A by default

Where M4A Files Come From

  • Apple Music
  • iTunes Store
  • iPhone/iPad recordings
  • Voice Memos app
10x
Faster than real-time
Get your M4A captions in minutes
99%
Accuracy rate
Industry-leading AI for M4A files
53+
Languages
Captions in any language
30+
Export formats
SRT, VTT, SCC, and more
How It Works

Create captions from M4A in 6 steps

Step 1

Create account

Sign up for Sonix's free trial. Includes 30 minutes free.

Step 2

Upload file

Upload your M4A file from your computer or cloud storage.

Step 3

Select language

Choose from 53+ languages spoken in your file.

Step 4

Auto-transcribe

Sonix AI transcribes your M4A with word-level timestamps.

Step 5

Edit captions

Fine-tune timing and formatting for accessibility.

Step 6

Export

Download closed captions in SRT, VTT, or SCC format.

Common Questions

Everything about M4A captions

What's the difference between captions and subtitles for M4A?

Captions include speaker identification and sound descriptions for deaf viewers. Subtitles focus on dialogue translation. For accessibility, choose captions.

Are M4A-to-caption conversions ADA compliant?

Sonix generates captions meeting ADA requirements when you include speaker labels and review for accuracy. M4A's quality helps achieve high accuracy.

Can I caption iPhone Voice Memos?

Yes! Voice Memos in M4A format work perfectly for creating accessible captions. Great for making recorded content available to deaf viewers.

How do I add speaker labels to M4A captions?

Sonix automatically detects speakers during transcription. Customize names before exporting captions. Speaker labels appear at the start of each segment.

What caption format works for broadcast M4A?

For broadcast television, export to SCC or STL formats which meet FCC requirements. Sonix supports professional broadcast formats.

How accurate are AI captions from M4A?

Sonix achieves 99%+ accuracy on clear M4A audio. For professional captioning, a quick human review ensures perfection.

Why Sonix

Accessible captions from M4A files

Accessibility First

Create captions that make your content accessible to deaf and hard-of-hearing viewers.

ADA Compliant

Meet accessibility requirements with properly formatted closed captions.

Sound Descriptions

Add non-speech elements like [music] and [applause] for full context.

SEO Benefits

Captions make video content searchable and improve discoverability.

Related

More ways to convert M4A files

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Other file formats

WMA to text
OGA to text
WAV to text
MTS to text
MPGA to text
XSPF to text
AAC to text
AIFF to text
OPUS to text
MP2 to text
See all supported file formats
Reviews

Trusted by accessibility teams

4.98 rating from 211 reviews

I'm a journalist and I'm finding that Sonix is a very valuable tool.
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Curtis F.
Gainesville, FL USA
The app is accurate, quick in response, and detailed in delivery. I am impressed.
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Lawrence A.
Lagos, Nigeria
Sooooooooooo easy to use and accurate.
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Jennifer K.
Seattle, WA USA
The speech to text was fast and very accurate.
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Janine G.
Cape Town, South Africa
Wow very cool. Sonix is so awesome. There will be huge demand for this. The editor will be really good for team sharing. Such a great platform.
KT
Karla T.
Toronto, Canada
I tried Sonix for the first time and I was astonished by the incredibile conversion accuracy.
RC
Rosario C.
Milan, Italy
It was super easy, affordable, and accurate!
AL
Allison L.
Ellsworth, WI, USA
Thank you for all of your help with my dissertation!!! Ya'll rock!!
MA
Miranda A.
Houston, TX
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