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Actually FLAC and Opus support was added to the Core Audio / AudioToolbox / AVFoundation APIs in iOS 11. Though the Opus decoder only supports raw packet decoding, i.e. you still need something to decode the container (usually ogg).

Also, FLAC file decoding is horribly slow - compared to the FOSS reference decoder -, because for some reason the whole file is scanned through on the first read when using the AudioFile APIs (AudioFileReadPacketData). (I’m gonna make a demonstration project for this and send them a bugreport tomorrow.)




Fyi, here’s the demonstration project I talked about: https://github.com/tzahola/AudioFileFLACBug


So bizarre to write their own decoder, especially given libFLAC is BSD licensed.


It actually makes sense, because libFLAC has no public API for getting the compressed audio packets as is. Rice/huffmann/whatever decompression always happens inside libFLAC.

With Apple’s AudioFile API you can decide whether you want the decompressed PCM samples, or the underlying compressed packets. You can get better energy efficiency if you offload the decompression step to the dedicated coprocessor. The difference is smaller than with hardware vs software h.264 decoding, but there is a difference.

(For lossy codecs this also makes sense when you want to forward the compressed packets to a wireless speaker in order to avoid lossy recompression on Bluetooth transmission.)




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