[FFmpeg-devel] [WIP] lavfi: add showaudio filter
stefasab at gmail.com
Tue Dec 27 19:20:04 CET 2011
On date Tuesday 2011-12-27 14:58:03 +0100, Stefano Sabatini encoded:
> On date Monday 2011-12-26 00:14:39 +0100, Stefano Sabatini encoded:
> > Subject: [PATCH] lavfi: add showaudio filter
> > ---
> > libavfilter/Makefile | 3 +-
> > libavfilter/allfilters.c | 3 +
> > libavfilter/avf_showaudio.c | 174 +++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 179 insertions(+), 1 deletions(-)
> > create mode 100644 libavfilter/avf_showaudio.
> Main problem is now to understand how to visualize N samples in a
> packet using only w columns.
> One possibility: w defines the number of samples to visualize, this
> means that we have to visualize samplerate/w frames, i.e.:
> rate = samplerate/w
> For example with w=640, samplerate=22100:
> rate = 22100/640 ~= 35
> Alternatively I could fix the rate, and scale the image accordingly by
> samples_to_show = samplerate / rate
> For example with rate = 10, samplerate = 22100
> samples_to_show = 22100 / 10 = 2210
> and I could use lsws to scale such an image to make it suit w.
Updated implementing the first option.
* multiple channels support, every channel may be displayed on a
separate area a-la ffplay or on the same area, possibly letting the
user choose the color for each channel wave.
> RDFT should be easier to add (same for some power/volume
Due to different caching logic this could be a separate filter
(e.g. showaudio -> showwaves, showrdft?).
> For more complex audio visualizations we may consider to write a
> MilkDrop/ProjectM wrapper.
Started to look at this, it's quite complex due to the use of C++ and
to the opaque API (I can't still guess how to just get the video data
out of the SDL/GL mess). Hints are welcome if you have experience with
it (IIRC at least VLC has/planned to have a projectm wrapper, don't
know how it ended).
FFmpeg = Faithless & Faithful Most Plastic Egregious Gargoyle
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