Convert FLAC to captions

Create accessible closed captions from your lossless FLAC audio. Professional-quality captions from the highest quality source audio.

Free to start — no credit card required.See pricing

ADA compliant
5-min turnaround
Accessible
FLAC conversion guide

Create captions from FLAC in 6 steps

  1. 1
    Create account~30 sec

    Sign up for a free Sonix trial with 30 free minutes.

  2. 2
    Upload file~1 min

    Upload your FLAC file from your computer or cloud storage.

    44+ formats supported
  3. 3
    Select language~10 sec

    Select the language spoken in your file.

    54+ languages
  4. 4
    Auto-transcribe~5 min

    Sonix AI transcribes your FLAC with word-level timestamps.

  5. 5
    Edit captions~2 min

    Fine-tune timing and formatting for accessibility.

  6. 6
    Export~10 sec

    Download your closed captions as SRT or VTT files.

    30+ export formats
The FLAC file format

Understanding FLAC files

What is a FLAC file?

Lossless audio compression - CD quality at half the size

Free Lossless Audio Codec file (FLAC) is an audio format similar to MP3, but lossless. What does this mean? The audio in a FLAC file is compressed without any loss in quality, whereas a MP3 file compresses the audio but usually lowers the quality of the file by excluding certain frequencies. A FLAC file works similar to how a ZIP file is compressed. Since FLAC is highly optimized for audio, you’ll receive a better compression ratio when compared to the ZIP compression algorithms. You can play compressed FLAC files in your favorite media player (including VLC, your car, or home stereo, or computer) just like you would an MP3 file (without having to uncompress it separately).
FLAC files are one of the fastest and most widely supported lossless audio codecs and is one of the few that are non-proprietary and has a well-documented open-source reference implementation. There are no attached patents for FLAC files. It was developed in 2000 and FLAC files discourage developers to not include any DRM features.

Common uses for FLAC files

  • Audiophile music collections
  • Music archiving
  • High-fidelity audio
  • Lossless music streaming
  • Bandcamp downloads
  • HD music stores
  • Audio archivists
  • Tidal streaming rips

Who works with FLAC files?

Oral historians, university and library digitization teams, and field researchers rely on FLAC to preserve interviews and recordings as archival masters, since the compressed file decodes bit-for-bit identical to the original. Podcast producers, radio engineers, and mastering studios also keep FLAC versions of episodes and sessions so they can re-edit or re-export later without generational quality loss.

FLAC vs WAV: which should you use?

Both FLAC and WAV are lossless, but WAV stores audio uncompressed while FLAC compresses it to roughly half to two-thirds of the size with no change to the decoded audio. FLAC also has built-in metadata tagging and per-frame checksums for verifying file integrity, features WAV largely lacks. Choose WAV when working inside recording and editing software that expects raw PCM; choose FLAC for long-term archiving, distribution, or uploads where smaller files save storage and transfer time.

Convert WAV to text
10x
Faster than real-time
Get your FLAC captions in minutes
99%
Accuracy rate
Industry-leading AI for FLAC files
53+
Languages
Captions in any language
30+
Export formats
SRT, VTT, and TTML
FLAC conversion FAQ

FLAC captions: frequently asked questions

Why use FLAC for professional captions?

FLAC's lossless audio provides the clearest source for caption transcription. When accuracy is critical, FLAC source files deliver the best possible results.

Are FLAC-to-caption conversions ADA compliant?

Sonix generates captions meeting ADA requirements. FLAC's perfect quality helps achieve accuracy levels exceeding professional captioning standards.

Can I add sound descriptions to FLAC captions?

Yes! After transcription, add non-speech descriptions like [music], [applause], or [door closes] in Sonix's editor.

How accurate are AI captions from FLAC?

Sonix achieves 99%+ accuracy on clear FLAC audio, often exceeding this due to the pristine lossless quality.

What caption format works for broadcast FLAC?

For broadcast television, export to TTML formats which meet FCC requirements.

Can I caption FLAC files with multiple speakers?

Yes! Speaker detection works excellently with FLAC's perfect audio quality. Each speaker gets labeled captions.

Do I need to convert FLAC to MP3 before transcribing?

No. FLAC files can be uploaded and transcribed directly, and skipping the MP3 conversion avoids an unnecessary lossy re-encode of your audio.

Why won't my FLAC file play in iTunes or Apple Music?

Apple's media apps do not natively support FLAC; Apple uses its own lossless codec, ALAC. You can play FLAC on Apple devices through the Files app or a third-party player, or convert the file to ALAC or AAC for library use.

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