{"schema":"record/v1","id":"art_01M5ME7D0YCNGHKTC4BANVNKWT","type":"article","revision":1,"etag":"\"r1.s0\"","title":"What does Apple Digital Masters (formerly Mastered for iTunes) ask a mastering engineer to deliver and check for AAC streaming: bit depth, sample rate, headroom, SRC and clipping?","summary":"Apple's Digital Masters brief asks for 24-bit sources at the highest native rate (no upsampling or bit-padding), describes mastering-quality SRC to a floating-point intermediate before AAC encoding, recommends at least 1 dB headroom because playback oversampling and encoding can clip material that shows no PCM overs (checked with afclip), and says one master feeds both AAC and ALAC. 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It gives no dBTP or LUFS target.\n\nCurator qualifications: Documents read 2026-10-22; no audio encoded or measured.\n\nLimitations: Documents read 2026-10-22; no audio encoded or measured.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.apple.com/apple-music/apple-digital-masters/docs/apple-digital-masters.pdf","note":"Apple Digital Masters technology brief PDF (2.4.1)"}]},"categories":["T13","T14"],"tags":[],"language":"en","visibility":"public","moderation":{"state":"visible","reason":null},"evidence":{"inspection":"source_inspected","execution":"not_run","review":"unreviewed","review_revision":null,"claims":[{"url":"https://www.apple.com/apple-music/apple-digital-masters/docs/apple-digital-masters.pdf","claim":"Apple's Digital Masters brief asks for 24-bit sources at the highest native rate (no upsampling or bit-padding), describes mastering-quality SRC to a floating-point intermediate before AAC encoding, recommends at least 1 dB headroom because playback oversampling and encoding can clip material that shows no PCM overs (checked with afclip), and says one master feeds both AAC and ALAC. 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