Default value 500.
@item first_pts
-Assume the first pts should be this value.
+Assume the first pts should be this value. The time base is 1 / sample rate.
This allows for padding/trimming at the start of stream. By default, no
assumption is made about the first frame's expected pts, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
-silence if an audio stream starts after the video stream.
+silence if an audio stream starts after the video stream or to trim any samples
+with a negative pts due to encoder delay.
@end table
@end example
@end itemize
-@section select
-Select frames to pass in output.
-
-It accepts in input an expression, which is evaluated for each input
-frame. If the expression is evaluated to a non-zero value, the frame
-is selected and passed to the output, otherwise it is discarded.
-
-The expression can contain the following constants:
-
-@table @option
-@item n
-the sequential number of the filtered frame, starting from 0
-
-@item selected_n
-the sequential number of the selected frame, starting from 0
-
-@item prev_selected_n
-the sequential number of the last selected frame, NAN if undefined
-
-@item TB
-timebase of the input timestamps
-
-@item pts
-the PTS (Presentation TimeStamp) of the filtered video frame,
-expressed in @var{TB} units, NAN if undefined
-
-@item t
-the PTS (Presentation TimeStamp) of the filtered video frame,
-expressed in seconds, NAN if undefined
-
-@item prev_pts
-the PTS of the previously filtered video frame, NAN if undefined
-
-@item prev_selected_pts
-the PTS of the last previously filtered video frame, NAN if undefined
-
-@item prev_selected_t
-the PTS of the last previously selected video frame, NAN if undefined
-
-@item start_pts
-the PTS of the first video frame in the video, NAN if undefined
-
-@item start_t
-the time of the first video frame in the video, NAN if undefined
-
-@item pict_type
-the type of the filtered frame, can assume one of the following
-values:
-@table @option
-@item I
-@item P
-@item B
-@item S
-@item SI
-@item SP
-@item BI
-@end table
-
-@item interlace_type
-the frame interlace type, can assume one of the following values:
-@table @option
-@item PROGRESSIVE
-the frame is progressive (not interlaced)
-@item TOPFIRST
-the frame is top-field-first
-@item BOTTOMFIRST
-the frame is bottom-field-first
-@end table
-
-@item key
-1 if the filtered frame is a key-frame, 0 otherwise
-
-@item pos
-the position in the file of the filtered frame, -1 if the information
-is not available (e.g. for synthetic video)
-
-@item scene
-value between 0 and 1 to indicate a new scene; a low value reflects a low
-probability for the current frame to introduce a new scene, while a higher
-value means the current frame is more likely to be one (see the example below)
-
-@end table
-
-The default value of the select expression is "1".
-
-Some examples follow:
-
-@example
-# select all frames in input
-select
-
-# the above is the same as:
-select=1
-
-# skip all frames:
-select=0
-
-# select only I-frames
-select='eq(pict_type\,I)'
-
-# select one frame every 100
-select='not(mod(n\,100))'
-
-# select only frames contained in the 10-20 time interval
-select='gte(t\,10)*lte(t\,20)'
-
-# select only I frames contained in the 10-20 time interval
-select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
-
-# select frames with a minimum distance of 10 seconds
-select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
-@end example
-
-Complete example to 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.
-
@section setdar, setsar
The @code{setdar} filter sets the Display Aspect Ratio for the filter
following filters (e.g. @code{fieldorder} or @code{yadif}).
This filter accepts a single option @option{mode}, which can be
-specified either by setting @code{mode=VALUE} either setting the
-value alone. Available values are:
+specified either by setting @code{mode=VALUE} or setting the value
+alone. Available values are:
@table @samp
@item auto
Below is a description of the currently available multimedia filters.
+@section aselect, select
+Select frames to pass in output.
+
+These filters accept a single option @option{expr} or @option{e}
+specifying the select expression, which can be specified either by
+specyfing @code{expr=VALUE} or specifying the expression
+alone.
+
+The select expression is evaluated for each input frame. If the
+evaluation result is a non-zero value, the frame is selected and
+passed to the output, otherwise it is discarded.
+
+The expression can contain the following constants:
+
+@table @option
+@item n
+the sequential number of the filtered frame, starting from 0
+
+@item selected_n
+the sequential number of the selected frame, starting from 0
+
+@item prev_selected_n
+the sequential number of the last selected frame, NAN if undefined
+
+@item TB
+timebase of the input timestamps
+
+@item pts
+the PTS (Presentation TimeStamp) of the filtered video frame,
+expressed in @var{TB} units, NAN if undefined
+
+@item t
+the PTS (Presentation TimeStamp) of the filtered video frame,
+expressed in seconds, NAN if undefined
+
+@item prev_pts
+the PTS of the previously filtered video frame, NAN if undefined
+
+@item prev_selected_pts
+the PTS of the last previously filtered video frame, NAN if undefined
+
+@item prev_selected_t
+the PTS of the last previously selected video frame, NAN if undefined
+
+@item start_pts
+the PTS of the first video frame in the video, NAN if undefined
+
+@item start_t
+the time of the first video frame in the video, NAN if undefined
+
+@item pict_type @emph{(video only)}
+the type of the filtered frame, can assume one of the following
+values:
+@table @option
+@item I
+@item P
+@item B
+@item S
+@item SI
+@item SP
+@item BI
+@end table
+
+@item interlace_type @emph{(video only)}
+the frame interlace type, can assume one of the following values:
+@table @option
+@item PROGRESSIVE
+the frame is progressive (not interlaced)
+@item TOPFIRST
+the frame is top-field-first
+@item BOTTOMFIRST
+the frame is bottom-field-first
+@end table
+
+@item consumed_sample_n @emph{(audio only)}
+the number of selected samples before the current frame
+
+@item samples_n @emph{(audio only)}
+the number of samples in the current frame
+
+@item sample_rate @emph{(audio only)}
+the input sample rate
+
+@item key
+1 if the filtered frame is a key-frame, 0 otherwise
+
+@item pos
+the position in the file of the filtered frame, -1 if the information
+is not available (e.g. for synthetic video)
+
+@item scene @emph{(video only)}
+value between 0 and 1 to indicate a new scene; a low value reflects a low
+probability for the current frame to introduce a new scene, while a higher
+value means the current frame is more likely to be one (see the example below)
+
+@end table
+
+The default value of the select expression is "1".
+
+@subsection Examples
+
+@itemize
+@item
+Select all frames in input:
+@example
+select
+@end example
+
+The example above is the same as:
+@example
+select=1
+@end example
+
+@item
+Skip all frames:
+@example
+select=0
+@end example
+
+@item
+Select only I-frames:
+@example
+select='eq(pict_type\,I)'
+@end example
+
+@item
+Select one frame every 100:
+@example
+select='not(mod(n\,100))'
+@end example
+
+@item
+Select only frames contained in the 10-20 time interval:
+@example
+select='gte(t\,10)*lte(t\,20)'
+@end example
+
+@item
+Select only I frames contained in the 10-20 time interval:
+@example
+select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
+@end example
+
+@item
+Select frames with a minimum distance of 10 seconds:
+@example
+select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
+@end example
+
+@item
+Use aselect to select only audio frames with samples number > 100:
+@example
+aselect='gt(samples_n\,100)'
+@end example
+
+@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.
+@end itemize
+
@section asendcmd, sendcmd
Send commands to filters in the filtergraph.
projects / ffmpeg / blobdiff