I do exactly that (in Obj-C) with AAC files and the AVAudioPCMBuffer’s
floatChannelData is indeed raw PCM data.
> On Jul 2, 2018, at 1:36 PM, Waverly Edwards <wedwa...@k2m.com> wrote:
>
> Would someone provide guidance on how I can decompress M4A and AAC files into
> memory as raw LPCM.
> I need to decompress M4A and AAC files, manipulate and recompress the files
> back to disk.
> Writing data from LPCM to M4A or AAC is not a problem (except AAC file
> durations are always wrong but will play)
>
> I can read .caf, .m4a, .aac files into the buffer using the below code but
> only the .caf files are actually raw and allow me to work directly with the
> buffer contents
>
> let file = try? AVAudioFile(forReading: url)
> let buffer = AVAudioPCMBuffer(pcmFormat: file!.processingFormat,
> frameCapacity: AVAudioFrameCount(file!.length))
> do {
> try file!.read(into: buffer!)
> } catch {
> // problem, do something
> }
>
> I looked into AVAudioCompressedBuffer but I do not see how I get the data
> into this type of buffer and how to expand this into raw data for manipulation
>
> If it matters, I am programming on OSX (Sierra).
>
> Any advice?
>
> Thank you,
>
>
> W.
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