FLAC (Free Lossless Audio Codec) is the audiophile and archival favourite: the size advantage of compression, with zero loss of audio data. It's used for music ripping where every detail matters, for archival recordings that need to outlast format generations, and for high-end interview capture where the source recording is the master and any transcription artefact you can avoid is a win.
FLAC vs WAV vs MP3 — what changes for transcription
For practical transcription accuracy, FLAC is identical to WAV: both are lossless, the engine sees identical waveforms after decoding. The difference is file size: a 1-hour stereo FLAC is typically 200–350 MB vs ~600 MB for the same recording as WAV — about half. Compared to MP3, FLAC carries the full uncompressed signal where MP3 has thrown away ~90% of the bits; the gap matters for noisy, low-volume, or unusually-spoken audio (heavy accents, technical jargon, overlapping voices) where every artefact-free decibel helps.
Where FLAC is the right input
Archival projects digitising tape, cassette, or vinyl into a permanent text+audio archive. Oral history projects capturing interviews that need to be both listened to (decades from now) and indexed (now). Audiobook publishers with master FLAC stems wanting an accurate transcript for ebook companion text or for accessibility captions. Music transcription of spoken-word tracks (poetry, monologue, comedy) where the artistic recording shouldn't be re-encoded.
Markdown structure for archival recordings
The structured Markdown output is especially valuable for archival use — a flat plain-text transcript becomes hard to navigate at hour-plus durations, while structured Markdown with section headings (## at topic shifts), punctuated paragraphs, and timestamps lets a researcher decades from now grep for a specific term and jump straight to the audio position. The Markdown is the index; the FLAC is the master.
Before / After
Before (PDF):
[FLAC audio file]
Lossless 16-bit 44.1 kHz stereo, 220 MB, 32 minutes
Metadata: Vorbis comment block (artist, album, recording date, archive ID)
(no extractable text — full-fidelity PCM waveform)
After (Markdown):
# Oral History — Margaret Williams (Recorded 1998-04-12)
## Childhood in Birmingham
[00:00:05] So you grew up in Birmingham, in the 1930s. That's right, born in 1929. Grew up on Soho Hill in Handsworth. My father worked at the BSA factory.
## The War Years
[00:01:42] What do you remember about the war? The first thing I remember is the night they bombed the city centre…
Frequently asked questions
Does FLAC give measurably better transcription than MP3?
For clean recordings, the difference is small — modern transcription engines are robust to typical MP3 compression. For noisy field recordings, low-volume voices, heavy accents, or technical jargon at the edge of the engine's training data, the lossless FLAC reduces error rates by a measurable amount. For archival work where a transcript is created once and used forever, the FLAC source is the right choice if you have it.
Are FLAC tag/metadata fields read?
Vorbis comment metadata (artist, album, recording date, custom archive IDs) is read for processing context but not directly preserved in the Markdown output. If you need the metadata in the output, paste it as a YAML front matter block by hand at the top of the .md file after conversion.
Can I transcribe high-resolution FLAC (24-bit/96 kHz)?
Yes — high-resolution FLAC files are accepted and decoded normally. The transcription engine internally downsamples to its working rate (16 kHz mono is plenty for speech), so the extra resolution isn't leveraged for accuracy, but the file uploads and converts without any pre-processing on your end.
How long does a 1-hour FLAC take to transcribe?
A few minutes — most of the time is the transcription engine processing audio, which runs faster than real time. Upload time depends on your connection and FLAC size (typically 200–350 MB for 1 hour stereo), so for a fibre connection the whole round trip is often under 5 minutes; for slower uploads, expect more upload-time-dominated total.
Can I use FLAC transcripts for accessibility captions?
Yes. Alongside the Markdown, the transcription tool can export SRT and VTT subtitle files directly, which is the format caption players expect. The Markdown itself is a structured reading document with timestamps rather than a caption file, so use the SRT/VTT export when you need captions and the Markdown when you need a searchable archive.