On Wed, May 14, 2014 at 06:54:45PM -0700, Ricky Huang wrote: > Hello all, > > I am currently examining avf_showspectrum.c and I have a few questions that I > am hoping you guys can clarify for me: > > (This is the command I am running, BTW: ./ffmpeg -i input.mp3 -filter_complex > showspectrum=mode=separate:color=intensity:slide=0:scale=cbrt -y output.avi) > > 1) First it is about the output: I am assuming the plotted image has time > horizontally, the frequency range vertically, and the intensity of color as > the amplitude. Is that correct? >
Yes > 2) In plot_spectrum_column() function, the code copies some amount of the > data to the rdft_data: > > s->rdft_data[ch][start + n] = p[n] * s->window_func_lut[start + n]; > > and then performs a av_rdft_calc() on the data. But it's never clear the > s->rdft_data array, does this mean the plot is cumulative over time? > see s->filled, which represents the amount of data loaded in rdft_data. It doesn't need to be cleared, the buffer content will be replaced, and when it's fully replaced a new av_rdft_calc() will occur. Every sample will be used only once, no accumulation. > > Thanks in advance. -- Clément B.
pgpJsghzt4xfn.pgp
Description: PGP signature
_______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
