Thanks for your suggestion. Adding -r 25 does indeed solve the problem.
Although I don't understand why it is required. The input framerate is
25 and it's detected correctly when I use the simpler filter chain.
Ah, I know why this happens, you need to use settb=1/FPS filter after vstack.
This happens because adrawgraph filter it order to not drop output
frames need to have same timebase as input audio. Otherwise you would
get different metadata values.
Also note that your FPS in this case is 48000/1024. ~= 46.xxx
48000 is the audio sample rate, but where does the 1024 come from?
I have a new example with testsrc2 and anoisesrc. There is no input file
required for reproducing.
There are two graphs: The first one uses signalstats and drawgraph, and
the second one uses astats and adrawgraph. The problem is that the two
graphs don't advance with the same speed in X direction. Do you have an
idea how to make them synchrone?The video width is the same in both
cases, otherwise vstack wouldn't work.
The speed of drawgraph is correct, 1 pixel per frame. The speed of
adrawgraph is too fast.
Other question: reset=1 in astats means that the calculation result is
reset after each frame. But how does the filter know when a frame ends,
if the input of this filter is only an audio signal?
c://ffmpeg/ffmpeg -f lavfi -i testsrc2=size=hd1080:duration=10:rate=25
-f lavfi -i anoisesrc=d=10:c=pink:r=48000 -lavfi
[0]signalstats,drawgraph=m1=lavfi.signalstats.YAVG:mode=line:slide=scroll:min=0:max=255,settb=1/25[G1];[1]astats=metadata=1:reset=1,adrawgraph=m1=lavfi.astats.1.RMS_level:mode=line:slide=scroll:min=-90:max=0,settb=1/25[G2];[G1][G2]vstack,settb=1/25
-r 25 -y test.mp4
Michael
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