[FFmpeg-user] What is the fastest way to run cropdetect on specificframes in the video?
dflett at bigpond.net.au
Thu Jul 28 13:42:01 CEST 2011
From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-bounces at ffmpeg.org]
On Behalf Of Matt Kim
Sent: Monday, 4 July 2011 04:40
To: ffmpeg-user at ffmpeg.org
Subject: [FFmpeg-user] What is the fastest way to run cropdetect on
specificframes in the video?
I am trying to run the cropdetect function from the libavfilter library in
the fastest way possible.
And so I am trying to only take a collection of video frames throughout the
video and run it through the cropdetect filter.
So far I have tried two methods:
1. Run FFmpeg 4 different times in parallel at 4 different seektimes using
the -ss option.
- Unfortunately for me--the -ss option does not seem to work quickly,
and so attempts to run through every frame before reaching the correct time.
This causes the -ss option to be the bottleneck. This maybe be an issue
with file itself and not FFmpeg.
2. Apply the "select" filter before "cropdetect".
- This method is even slower than the previous one. I'm assuming that
applying the select filter on each frame takes much time.
*I have heard that moving the -ss option around may speed up the
process--but unfortunately on all of the encoded files I am dealing
with--this method does not seem to help.
Does anyone have any advice on how I may be able to run cropdetect faster?
Right now my analysis (using the parallel method) takes about 1 sec per 1
minute. This can cause problems though--as a 3hour long video will take
about 3 minutes to analyze.
Here is an example of how I am running my cropdetect filter:
ffmpeg -i [input video] -vf
-ss 600 -t 100 -an -y null.mp4
Any help would be greatly appreciated.
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The only suggestion I have is putting -ss and -t before -i in your command
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