[Libav-user] av_rdft_calc() resulting buffer

[Ricky Huang]

Hello all,

According to a LAS blog post here: http://blog.pkh.me/p/6-las-lossy-audio-spotter.html.  It says that "the buffer is composed of couples of real and imaginary floats except for the two first ones which are the real parts of the first and last bins…" under the "Processing the audio data" section.

Does anyone know where that is documented?  I looked on ffmpeg's doc (http://www.ffmpeg.org/doxygen/2.2/group__lavc__fft.html#ga745b8757713a5a0f0347eddcc6ccc9a4) and sees nothing on that.  I also looked at the avf_showspectrum.c code and it doesn't seem to make the special case for those two positions.


Thanks in advance.
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