FFMPEG - lavfi examples

FFMPEG
lavfi (Libavfilter input virtual device.)

(The following notes are also in the description)
Here's a link: https://ffmpeg.org/ffmpeg-all.html#lavfi

I decided to try out some of the examples on lavfi in the online ffmpeg documentation given in section 26.12.2

Examples...

In the first example you create a color video stream and play it back with ffplay:

This is the code:
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ffplay -f lavfi -graph "color=c=pink [out0]" dummy
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Then I did the same command but removed the graph and "out0" labels:

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ffplay -f lavfi color=c=pink
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Then I created three different video test filtered sources and played them:

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ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1];testsrc,negate [out2]" test3
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There was an example to read an audio stream from a file using the amovie source and play it back with ffplay:

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ffplay -f lavfi "amovie=Doom666.mp3"
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(If you look hard you might be able to see the hidden image?)
I chose the Doom soundtrack because I knew that they had somehow put image into the sound, I don't understand it and I don't know how they did it.
There is a better visualisation in this link:

From: https://www.youtube.com/watch?v=yzFit0nldf4So


After doing ffplay examples I also found an ffmpeg example in the following link:

https://www.bogotobogo.com/FFMpeg/ffmpeg_video_test_patterns_src.php

This example will create a 10 second output, 30 fps (300 frames total):
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ffmpeg -f lavfi -i testsrc=duration=10:size=1920x1080:rate=30 testsrc.mp4
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There are some other examples on the links that I've provided, and the ffmpeg manual goes into more detail about what lavfi is.

00:00 intro
00:15 create color video stream
00:33 same command without -graph
01:00 command to play 3 test filtered sources
01:40 command to read and play audio of Doom
02:36 command to make video of testsrc

Thankyou for watching :)