AAC audio to text
An AAC file is one of the ten containers the upload field names, so it goes up as it is. The words come back line by line, each with the second it starts and the second it ends. One file is up to 64 MB and 120 minutes, the free plan is $0, Pro is $10 a month.
Two ways an AAC file reaches you
AAC is a codec, and a codec travels inside a container. When a phone or a voice recorder writes an .aac file, the audio is often a bare stream; when a video tool writes one, the same audio sits inside an MP4 box. Both cases end up here, and the only difference is what you call the file on your disk.
| What you have on disk | What to do | Why |
|---|---|---|
| A raw .aac file | upload it unchanged | aac is named in the accept list of the upload field |
| AAC inside an MP4 container, saved as .m4a | upload it unchanged | m4a is named in the accept list of the upload field |
| AAC inside an MP4 container, saved as .mp4 | upload it unchanged | mp4 is named in the accept list of the upload field |
| AAC inside a container with an unusual name | rename the copy to .m4a and upload that | the picker filters by extension and by the type the system reports |
What the limits mean for an AAC file
| Limit | Value | Source |
|---|---|---|
| Size of one file | 64 MB | transcrib.si/pricing.html, checked |
| Length of one file on Pro | 120 minutes | transcrib.si/pricing.html, checked |
| Length of one file on the free plan | 30 minutes | transcrib.si/pricing.html, checked |
| Files a day on the free plan | 3 | transcrib.si/pricing.html, checked |
| Free plan price | $0 | transcrib.si/pricing.html, checked |
| Pro price | $10 a month paid yearly ($120 a year), or $20 a month paid monthly | transcrib.si/pricing.html, checked |
| Audio covered by Pro a month | 1,500 minutes of fair use | transcrib.si/pricing.html, checked |
Speakers, timecodes and exports
Switch on “Split by speaker” and the lines are grouped by voice — the same request that the speaker labels page compares across seven services. Every line keeps its timecodes, so the text can be lined up against the recording or exported as subtitles in SRT or VTT. Plain text is TXT or Markdown, tabular output is CSV, and DOCX is there on Pro. The meeting guide shows how to use all of it on one recording.
Where the recording is read
An AAC file in Russian is processed on our own transcription infrastructure, outside the United States. A file that is entirely in English can be passed to a third-party cloud speech provider in the United States when that fallback is enabled. The audio is used to produce the transcript and to run the service; it is never sold and never used to train models for other customers. Deleting the transcript deletes the audio with it, and the file leaves the live system immediately and the encrypted backups within 30 days. The privacy policy and the security notes spell this out.
If the upload is refused
- The file is over 64 MB. AAC is a compressed format, so this usually means a very long recording. Split it, or move to the guide for long recordings.
- The free plan says the file is too long. Free accepts up to 30 minutes; Pro takes files up to 120 minutes.
- The picker does not show your file. Rename a copy to .m4a or .mp4 and try again — both are in the accept list.
- The sound is broken. A recording cut short stays cut short; no service can invent the missing end of it.
The other containers
The upload field of the site names ten of them: mp3, wav, m4a, mp4, webm, ogg, flac, aac, wma and mov. All of them go through one pipeline and return the same structure, so an AAC recording and an MP3 of the same hour give the same text. The general guide lists every format with the limits next to them.
Put a file on the page and read the first lines.
The widget below is the same one as on the home page: file → transcript with timecodes and speakers → export. The transcript is saved to your account.
Drop an audio or video file
or — mp3, wav, m4a, mp4, up to 64 MB and two hours
Transcription runs under your account: sign in or create a free account.
No account yet? The free plan needs no card. Create a free account or sign in.
Questions this page answers.
Is a raw .aac file accepted?
Yes. The upload field of the site names aac among the ten containers it takes, and the file is read exactly as it was written.
My AAC file is really an MP4 with a wrong name. What do I do?
Make a copy and name it .m4a or .mp4. Both extensions are in the accept list, so the picker will show the file and the server will read the container as it is.
How long can an AAC recording be?
Up to 120 minutes and 64 MB per file on Pro and Team. The free plan takes files up to 30 minutes and 3 files a day.
Can the speakers be told apart?
Yes, and on every plan. Tick “Split by speaker” and the lines are marked with the voice they belong to, exactly like on the MOV page.
Do you publish an accuracy number?
No. The site publishes no single accuracy figure — ask for the evaluation report and the sample set and we will send them.
Related pages.
The picture is ignored, the sound is not.
A Windows recording, uploaded as it is.
Where most AAC recordings come from.
The Russian path through our engine.
What six services publish about their own numbers.
The plans and the limits.
Mark Burmistrov, Founder.
Every number on this page comes from the service contract, the pricing page or our own measurements. The author of the page and the publisher of the site are the same person. Questions and corrections: support@transcrib.si.