[FFmpeg-devel] [PATCH] doc/filters: itemize select/aselect examples
Stefano Sabatini
stefasab at gmail.com
Tue Dec 11 23:42:44 CET 2012
Improve rendering.
---
doc/filters.texi | 50 ++++++++++++++++++++++++++++++++++++++------------
1 file changed, 38 insertions(+), 12 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 679715d..cea6384 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -4728,45 +4728,71 @@ value means the current frame is more likely to be one (see the example below)
The default value of the select expression is "1".
-Some examples follow:
+ at subsection Examples
+ at itemize
+ at item
+Select all frames in input:
@example
-# select all frames in input
select
+ at end example
-# the above is the same as:
+The example above is the same as:
+ at example
select=1
+ at end example
-# skip all frames:
+ at item
+Skip all frames:
+ at example
select=0
+ at end example
-# select only I-frames
+ at item
+Select only I-frames:
+ at example
select='eq(pict_type\,I)'
+ at end example
-# select one frame every 100
+ at item
+Select one frame every 100:
+ at example
select='not(mod(n\,100))'
+ at end example
-# select only frames contained in the 10-20 time interval
+ at item
+Select only frames contained in the 10-20 time interval:
+ at example
select='gte(t\,10)*lte(t\,20)'
+ at end example
-# select only I frames contained in the 10-20 time interval
+ at item
+Select only I frames contained in the 10-20 time interval:
+ at example
select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
+ at end example
-# select frames with a minimum distance of 10 seconds
+ at item
+Select frames with a minimum distance of 10 seconds:
+ at example
select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
+ at end example
-# use aselect to select only audio frames with samples number > 100
+ at item
+Use aselect to select only audio frames with samples number > 100:
+ at example
aselect='gt(samples_n\,100)'
@end example
-Complete example to create a mosaic of the first scenes:
-
+ at item
+Create a mosaic of the first scenes:
@example
ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
@end example
Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
choice.
+ at end itemize
@section asendcmd, sendcmd
--
1.7.9.5
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