Thank you Clement, your answers helped. On May 15, 2014, at 12:05 AM, Clément Bœsch <[email protected]> wrote:
> 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. > _______________________________________________ > Libav-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/libav-user
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