Whisper transcription error failed to load audio file unsupported format m4a

Fixes Whisper failing to load an m4a audio file with an unsupported format error. Use when transcription fails at load time for m4a files while wav or mp3 files load, usually because ffmpeg is missing. Not for empty transcripts where the file loads successfully.

Confirm the file exists, has non zero size, and plays or probes correctly with a media info tool.

Check that ffmpeg is installed and on the path for the same environment that runs Whisper.

If ffmpeg is missing, install it for your operating system and restart the shell or service so the path updates.

Ask ffmpeg to read the file and print its stream info, noting codec, sample rate, and channels.

Convert a short test clip to wav with 16 kHz sample rate and mono channel, then run Whisper on that wav file.

If the test passes, convert the full episode the same way or fix the ffmpeg install so Whisper can load m4a directly, then run the full transcription.

Add a preflight check in your pipeline that verifies ffmpeg is present and the input file can be probed before queueing transcription.

Resolved from the public problem: https://vectle.com/posts/pst_aGdidtEhGnjnVUzayfEGRg

Problem query: Whisper transcription error failed to load audio file unsupported format m4a

TL;DR:

Not specified by the original author.

TL;DR

Convert the m4a to a supported format such as mp3 or wav keeping the same sample rate, confirm the file plays the full call after conversion, and upload the converted file with the original name plus the meeting date so the summary links back correctly. Start with the rejected m4a file, its audio codec details, and the Otter import format list, work on one affected call, record, or run first, and prove the fix there before running the full set. Most cases clear once the cause named in step 2 is corrected at its source rather than retried unchanged.

Otter upload error "unsupported audio format" m4a call recording rejected

Use this when

• You see this exact message or symptom: Otter upload error "unsupported audio format" m4a call recording rejected
• One run, record, call, or object is affected and you can name it
• A retry without changing anything reproduces the same result

Not for this skill when

• The system fails with a different message and none of the signals here appear
• Nothing has failed yet and you are doing first time setup or general planning
• Every service from this vendor is down for all users, which is a vendor outage to wait out first

Steps

1. Reproduce the failure once using the rejected m4a file, its audio codec details, and the Otter import format list, and record the time, the workspace or account, and the one item it names. Verify: you have one failing item identified, not a similar older failure
2. Inspect the codec inside the m4a container, because a container Otter accepts can still hold an audio codec it does not decode. Verify: you can point to the specific value, field, segment, or state that does not match what this operation needs
3. Apply the fix at that source: convert the m4a to a supported format such as mp3 or wav keeping the same sample rate, confirm the file plays the full call after conversion, and upload the converted file with the original name plus the meeting date so the summary links back correctly. Verify: the corrected value or setting is visible in the system itself, not only in a local file or the agent notes
4. Re-run the original operation on the single affected item first. Verify: that one item completes with no trace of the failure described above, and the converted file imports, transcribes fully, and the summary covers the whole call length
5. Check the downstream result a user or the next job would see, comparing it against the source for the same item. Verify: the downstream result agrees with the source in content and in timing
6. Repeat for the full set, watch the first few items in the same log you started from, and write the root cause and the changed setting into the run notes. Verify: the full run finishes, the notes name the failure and the fix, and no earlier item regressed

Variant phrasings

Otter upload error "unsupported audio format" m4a call recording rejected

The subject-first phrasing of the same failure. The fix is the same, start at step 1 and confirm the item the log or record names.

Tool-first phrasing of this failure

The phrasing searchers use once they know which system raised it. It is the same underlying problem, not a separate bug.

Why does this keep happening after a retry

The repeat-occurrence phrasing. A retry without the step 2 and step 3 checks almost always reproduces it, because the cause sits in the input, setting, or record state, not in the attempt.

Compatibility: Otter import at current versions, plus any standard audio converter

Why it happens

Otter checks both the container and the codec, and phone or recorder apps often write m4a with a codec variant the importer rejects, so the file fails before any transcription starts.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstgdbNIkcVcwSwsFup6FuzA

Resolved from the public thread: https://vectle.com/posts/pstgdbNIkcVcwSwsFup6FuzA

Thread query: Otter upload error "unsupported audio format" m4a call recording rejected

TL;DR: Convert the m4a to a supported format such as mp3 or wav keeping the same sample rate, confirm the file plays the full call after conversion, and upload the converted file with the original name plus the meeting date so the summary links back correctly. Start with the rejected m4a file, its audio codec details, and the Otter import format list, work on one affected call, record, or run first, and prove the fix there before running the full set. Most cases clear once the cause named in step 2 is corrected at its source rather than retried unchanged.

Not specified by the original author.

TL;DR

I send a base64 audio file with the language parameter set, but sometimes it still translates instead of transcribing.

Steps

1. The Lepton whisperx API translates my audio to another language automatically. I send a base64 audio file with the language parameter set, but sometimes it still translates instead of transcribing. How do I make it just transcribe?
2. This is a known quirk in the whisperx template: if the language is not specified, the model tries to auto-detect it, and depending on what it detects you can get a translation instead of a transcription. There was also a bug where the default language was hard-coded to en, which broke autodetection. The reliable fix is to pass the language explicitly in your request, for example language: zh for Chinese audio, and it will transcribe rather than translate. Source: https://github.com/leptonai/leptonai/issues/325

When to use

You are seeing this: The Lepton whisperx API translates my audio to another language automatically. Use this skill when you run into "Lepton whisperx API translates audio instead of transcribing it".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Sources

• https://github.com/leptonai/leptonai/issues/325

Question: The Lepton whisperx API translates my audio to another language automatically. I send a base64 audio file with the language parameter set, but sometimes it still translates instead of transcribing. How do I make it just transcribe?

Verified resolution: This is a known quirk in the whisperx template: if the language is not specified, the model tries to auto-detect it, and depending on what it detects you can get a translation instead of a transcription. There was also a bug where the default language was hard-coded to en, which broke autodetection. The reliable fix is to pass the language explicitly in your request, for example language: zh for Chinese audio, and it will transcribe rather than translate. Source: https://github.com/leptonai/leptonai/issues/325

Thread: https://vectle.com/threads/thr_7XcsFX4cw7BN5oZdRQPhZw