[FFmpeg-devel] [PATCH] lavfi: add drawgraph filter

[Dave Rice]

Hi,

> On Jun 26, 2015, at 11:27 AM, Paul B Mahol <onemda at gmail.com> wrote:
> 
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
> Waiting for comments and flames.

Here are some comments and flames:

I noticed that when I set min to a value greater than max. I get a crash with "Bus error: 10".

There may be an issue with negative values for min/max. When I run:
ffplay -f lavfi -i color=gray -vf signalstats,drawgraph=lavfi.signalstats.YAVG:min=0:max=255
I see a line scroll across the center of the window. When I change min to -255 I see a line at ~3/4 down the frame, where I would expect -128 to be. Does the min and max expect non-negative numbers.

It could be helpful to include equations within foreground, such as:
ffplay -i movie.mkv -vf "signalstats,drawgraph=lavfi.signalstats.YAVG:min=0:max=255:foreground=if(gt(lavfi.signalstats.YAVG\,128)\,green\,red)"
or actually I could probably subsequently use geq to accomplish that.

Can you alias 's' for 'size' as many of the other filters do.

This is very helpful, thanks!
Dave