From: Michael Koch <astroelectronic@t-online.de>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH] avutil/eval: Use even better PRNG
Date: Fri, 19 Jan 2024 09:53:46 +0100
Message-ID: <4d214d22-e1af-9374-1a66-886ca1692ad5@t-online.de> (raw)
In-Reply-To: <20240109015521.26231-1-michael@niedermayer.cc>
There is still a small problem with the random generator, but this has
nothing to do with the recent changes.
If the random() expression is used in the geq filter, then multiple
pixels get the same sequence of random numbers.
As can be shown with this command, where the frame has only two pixels:
ffmpeg -loglevel repeat -f lavfi -i nullsrc=size=1x2,format=gray -vf
"geq=lum='print(random(0));print(random(0));print(random(0))'" -frames 1
-y out.png
I think it's because the filter is executed in multiple threads.
-filter_threads 1 fixes the problem, but it slows down the whole filter
thread.
Michael
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next prev parent reply other threads:[~2024-01-19 9:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-09 1:55 Michael Niedermayer
2024-01-10 22:48 ` Stefano Sabatini
2024-01-11 2:39 ` Michael Niedermayer
2024-01-19 8:53 ` Michael Koch [this message]
2024-01-20 0:33 ` Michael Niedermayer
2024-01-13 3:51 Michael Niedermayer
2024-01-14 14:14 ` Stefano Sabatini
2024-01-16 0:27 ` Michael Niedermayer
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