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Can someone please post, in as much detail as possible, which AAC audio profile and bitrate settings Quicktime utilizes during an export on OS X Mavericks (10.9) when choosing File > Export > Audio Only... using a 16-bit 44100 Hz .wav file as a reference

I can observe, using the Inspector window in QuickTime, that the exported files approximate 256kbps (VBR?) and are 48000 Hz, but I want more precise and complete information.

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Can you supply a sample? By QuickTime X you mean version 10? (Disclaimer, I don't run Mavericks yet.) – slhck Nov 22 '13 at 16:28
@slhck I do mean version 10. I'm sorry for the confusion. I have removed that Roman numeral reference from the question. – jsejcksn Nov 29 '13 at 21:35

The default bit rate mode in QuickTime has been ABR for a long time.

Average Bit Rate (ABR) - Default Mode

-- Recommended for controlling file size --

A target bit rate is achieved over a long-term average (typically after the first few seconds of encoding). Unlike CBR mode, this mode does not provide constant delay when using constant bit rate transmission, but this mode provides almost best global quality while still being able to strictly control the resulting file size.

This, and more mathematical information can be found in Technical Note TN2271 -- Bit Rate Control Modes for AAC Encoding.

Note that if you want control, you can use iTunes to set VBR/ABR, bitrate and HE-AAC.

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