fix(ios): push the frames AVAudioConverter actually produced in the recorder callback#1097
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mdydek merged 2 commits intoJun 11, 2026
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…ecorder callback convertToBuffer:error:withInputFromBlock: sets frameLength to the number of frames it wrote, but the recorder callback overwrote it with a computed estimate and pushed ceil(numFrames * ratio) frames into the circular buffer. When the SRC's filter phase produced fewer frames than the estimate, the extra pushed samples were stale data from a previous render block - an audible click at nearly every block boundary whenever the requested callback rate differs from the hardware input rate. Fixes software-mansion#1096
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Jun 11, 2026
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Closes #1096
None.
Introduced changes
IOSRecorderCallback::taskOffloaderFunctionnow pushesconverterOutputBuffer_.frameLength— the frame countAVAudioConverteractually produced — into the circular buffer, instead of aceil(numFrames * ratio)estimate.converterOutputBuffer_.frameLength = ...assignment that was overwriting the converter's real output count with that estimate.Why
The SRC's filter phase makes per-call output fluctuate around
numFrames * ratio(a 512-frame block at 48 kHz → 16 kHz yields 170 or 171 frames depending on accumulated phase). Whenever the converter produced fewer frames than theceil()estimate, the extra pushed samples were stale data from a previous render block — a single-sample impulse (audible click) at nearly every block boundary, in every recording where the requestedonAudioReadysample rate differs from the hardware input rate. Full analysis with PCM evidence in #1096.Android is unaffected:
AndroidRecorderCallbackalready uses the produced count reported byma_data_converter_process_pcm_frames.Checklist