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

[Dave Rice]

> On Jun 28, 2015, at 1:54 PM, Paul B Mahol <onemda at gmail.com> wrote:
> 
> On 6/28/15, Dave Rice <dave at dericed.com> wrote:
>> 
>>> On Jun 28, 2015, at 11:07 AM, Paul B Mahol <onemda at gmail.com> wrote:
>>> 
>>> On 6/28/15, Dave Rice <dave at dericed.com> wrote:
>>>> Hi,
>>>> 
>>>>> On Jun 27, 2015, at 4:52 PM, Paul B Mahol <onemda at gmail.com> wrote:
>>>>> 
>>>>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>>>>> ---
>>>>> doc/filters.texi           |  76 ++++++++++++
>>>>> libavfilter/Makefile       |   1 +
>>>>> libavfilter/allfilters.c   |   1 +
>>>>> libavfilter/vf_drawgraph.c | 297
>>>>> +++++++++++++++++++++++++++++++++++++++++++++
>>>>> 4 files changed, 375 insertions(+)
>>>>> create mode 100644 libavfilter/vf_drawgraph.c
>>>>> 
>>> 
>>> [...]
>>> 
>>>> 
>>>> With this version using a color name for foreground no longer works:
>>>> 
>>>> This works:
>>>> ffplay -f lavfi -i mandelbrot -vf
>>>> signalstats,drawgraph=metadata=lavfi.signalstats.YAVG:min=0:max=255:slide=scroll:bg=green:fg=0x0000FF
>>>> 
>>>> This doesn't:
>>>> ffplay -f lavfi -i mandelbrot -vf
>>>> signalstats,drawgraph=metadata=lavfi.signalstats.YAVG:min=0:max=255:slide=scroll:bg=green:fg=red
>>> 
>>> AFAIK The expressions can not work with strings.
>>> 
>>>> 
>>>> Also here's an example with blend:
>>>> ffplay -f lavfi -i mandelbrot -vf "signalstats,split=3[a][b][c];\
>>>> [a]drawgraph=metadata=lavfi.signalstats.YAVG:min=0:max=255:slide=scroll:fg=0xFFFF0000:mode=dot[a1];\
>>>> [b]drawgraph=metadata=lavfi.signalstats.UAVG:min=0:max=255:slide=scroll:fg=0xFF00FF00:mode=dot[b1];\
>>>> [c]drawgraph=metadata=lavfi.signalstats.VAVG:min=0:max=255:slide=scroll:fg=0xFFFFFF00:mode=dot[c1];\
>>>> [a1][b1]blend=and[ab];[ab][c1]blend=and[out]"
>>>> 
>>> 
>>> The blending kills difference in colors so I may add multiple graphs
>>> support for filter.
>> 
>> Setting the background to black and blending seems a little better, though
>> I'm losing one of my graphs in this example.
>> 
>> ./ffplay -f lavfi -i mandelbrot -vf "signalstats,split=3[a][b][c];\
>> [a]drawgraph=lavfi.signalstats.YAVG:min=0:max=255:slide=scroll:bg=black:fg=0x0000FF:mode=dot[a1];\
>> [b]drawgraph=lavfi.signalstats.YLOW:min=0:max=255:slide=scroll:bg=black:fg=0x00FF00:mode=dot[b1];\
>> [c]drawgraph=lavfi.signalstats.YHIGH:min=0:max=255:slide=scroll:bg=black:fg=0xFF0000:mode=dot[c1];\
>> [a1][b1]blend=lighten,[c1]blend=lighten[out]"
>> 
>> Also the foreground expression is in ABGR or BGR.  This is the opposite
>> arrangement of what is specified here
>> http://ffmpeg.org/ffmpeg-utils.html#Color.
> 
> Using blend for this is SLOW.

If the background could set to full alpha, then multiple graphs could be added together with the overlay filter. I tested some alpha expressions with bg (black at 00, 0x00000000) and didn’t seem to get transparent results.

> Have you tried new 'line' mode?

Oooo, this is great. Probably more readable than dot in many situations.

> Also expressions allow changing color of dot/line/bar so try it and
> tell me if its fine.

I tested this with several modes and it works as expected (excepting that ABGR/BGR vs RGBA/RGB note). Thanks for adding this.

Some other comments:
I tried to use an equation within metadata but got no plotted result. For instance, "metadata=pow(lavfi.signalstats.YMIN\,2)”. There are some values that may occur in a wide range, so a logarithmic or mathematically adjusted display may be preferable.

Can input width and input height be used in variables within a size expression. In many cases I would like to draw the graph over the input video, but to do this I must know the input video size in advance.
Dave Rice