fix: support large audio files (>25 MB) for transcription#37
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Flask had no MAX_CONTENT_LENGTH set, causing Werkzeug to reject uploads over 25 MB before they reached the route handler — making the existing compression logic unreachable dead code. - Set MAX_CONTENT_LENGTH to 2 GB to accommodate long WAV recordings - Calculate compression bitrate dynamically based on audio duration so the output always fits under Whisper's 25 MB API limit, regardless of how long the recording is (previously hardcoded 64k caused failures on recordings longer than ~50 minutes) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
shaulams
approved these changes
Apr 11, 2026
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Problem
Uploading audio files larger than 25 MB failed with a 413 error. The app never set `MAX_CONTENT_LENGTH`, so Flask/Werkzeug silently enforced a 25 MB upload limit — making the existing compression logic unreachable dead code.
Changes
1. Set MAX_CONTENT_LENGTH to 2 GB
Covers ~120 min WAV recordings at broadcast quality (the stated use case).
2. Dynamic compression bitrate
The hardcoded `64k` bitrate caused failures on recordings longer than ~50 minutes — the compressed file still exceeded Whisper's 25 MB API limit. Bitrate is now calculated from audio duration to guarantee output stays under 24 MB, capped between 8–64 kbps. Whisper handles low bitrates well for speech.
Both interview and narration transcription paths are fixed.
Tested
Verified with a 777 MB / ~76 min WAV file that previously failed at upload and now transcribes successfully.