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The Sync API accepts short audio clips with the following constraints:
ConstraintValue
Minimum duration80 ms
Maximum duration120 s
Maximum file size40 MB
Sample width16-bit only
ChannelsMono or stereo (stereo is down-mixed internally)
Sample rates8000, 16000, 22050, 24000, 32000, 44100, 48000 Hz
FormatsWAV (audio/wav) or raw PCM S16LE (audio/pcm)
For WAV, the sample rate and channel count are read from the file header. For raw PCM, pass sample_rate and channels in the config part — see Sending raw PCM audio. Audio that violates a constraint is rejected with a 400, 413, or 415 — see Error handling for the full error table. For audio longer than 120 seconds, use Pre-recorded STT. For live audio, use Real-time STT.