Transcribe long recordings from a Sound Devices MixPre from poly WAV to one readable day.
An 8-hour documentary or interview day recorded on a Sound Devices MixPre transcribes in about 16 minutes once you export a mono or stereo mix from the polyphonic WAV. The first 20 minutes are free, and the 480 minutes fit a $6 pack of 500 with 20 to spare.
Many channels, one voice track
A MixPre packs every input into one polyphonic file. For a transcript, flatten it to a mix first.
What a poly WAV holds
By default a MixPre take on its SD card is a single polyphonic WAV with every input, and often a left-right mix, as channels inside one file. Editors open it as separate tracks. That shape is ideal for the sound mix and the wrong one to transcribe, so export a mix that holds every voice.
The size, channel by channel
Four channels at 24-bit, 48 kHz are 4 × 144,000 bytes a second, about 2.07 GB an hour, so eight hours is roughly 16.6 GB. A mono 16-bit mix of the same day is about 345 MB an hour, or 2.76 GB, and a 128 kbps MP3 is about 461 MB.
Exporting the mix
Open the take in your editor or the tool you use for dailies, balance the lavaliers and boom, and export one mono or stereo file. A mix above 2 GB starts once a pack is on the account; an MP3 uploads before one. If the upload refuses the file, convert it to MP3 first.
A day of interviews, searchable
The transcript returns in chapters with timestamps that match the takes, with interviewees named in the summary and key quotes. The names, places, numbers and dates said on camera are listed, which saves a fact-checking pass, and the chat finds a line across eight hours.
Polyphonic files elsewhere
A professional recorder writes a professional file, and a general upload box does not know what to do with it.
✗ How it usually goes
A clean day of sound, a messy route to text.
- The OpenAI Whisper API allows only 25 MB
- A 16 GB poly WAV with nowhere to go
- Channels transcribed one at a time
- The boom and lavs disagree on who spoke
- Takes logged by hand from the slate
- Selects chosen from memory
✓ One mix per day
Flattened, sent and read back in order.
- Mono or stereo mix under 5 GB
- A full eight-hour day returned in about 16 minutes
- Speakers named in the chapters
- Names and dates listed for fact-checks
- First 20 minutes free
- The day fits a $6 pack
Sample
A long documentary interview day, as it comes back.
This sample is illustrative and written for this page, not from a real film. Roles replace the names of the people on camera.
Export
One transcript. Five clean formats.
Every pack exports all five — no format is held back for a higher tier.
Plain text
De-ummed paragraphs. Ready to paste.
SRT captions
Timed to the speech. Every video editor reads this.
WebVTT
HTML5 player + YouTube uploads.
Show notes
Formatted with chapters and pull-quotes.
Machine-readable
Timestamped text for your own tools.
Pricing
Honest pricing, no surprises.
A pack from $6 (500 minutes) opens the full transcript. After that, no subscription and no auto-renew — every tier is a one-time minute pack, and credits never expire. Buy once, use the minutes whenever you need them.
Casual pack
$6/500 min
8 hours of audio — $0.72 an hour. One-time — credits never expire.
- 500 minutes of audio
- All export formats
- Unlimited AI chat per transcript
- Executive summary & key quote
Best value
$12/2,000 min
33 hours of audio — $0.36 an hour. Credits never expire.
- 2,000 minutes of audio
- Priority queue
- All export formats
- Unlimited AI chat per transcript
Bulk pack
$24/5,000 min
83 hours of audio — $0.29 an hour. Credits never expire.
- 5,000 minutes of audio
- Priority queue
- API access for batch pipelines
- All export formats
FAQ
Sound Devices MixPre recordings, the common questions.
How long does an 8-hour MixPre day take?
About 16 minutes. The longest file on the proof page, 9.31 hours, took 1,033 seconds.
What will an 8-hour MixPre day cost?
The first 20 minutes are free on a first visit, and the day uses 480 of the $6 pack's 500 minutes. For a series, four eight-hour days are 1,920 minutes and fit the $12 pack of 2,000; more than that belongs on the $24 pack of 5,000.
Can I upload the polyphonic WAV directly?
Export a mono or stereo mix instead. It keeps the file far smaller and makes sure every voice is in the audio that gets transcribed.
The MixPre ran past 10 hours. What then?
Export it as two files, each under 10 hours and 5 GB. Each returns as its own transcript with its own timestamps.
What languages can the contributors speak?
Any of the 99 languages detected automatically, Portuguese, Japanese and Afrikaans among them. An interview that switches languages is detected on its main one.
Which formats come back, and is the material kept private?
A shoot day exports to TXT, DOCX, SRT, VTT and JSON. Material for an unreleased film is handled privately: recordings are transcribed on our own servers and are never used for training.
Related
Production recorders and long shoots
Export the mix from the MixPre. The first 20 minutes of the day are on us.
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