Version 48 (modified by jdlh, 3 years ago) (diff)

Add description of filter syntax, especially filter options.

FFmpeg Filtering Guide

FFmpeg has access to many filters and more are added on a regular basis. To see what filters are available with your build see ffmpeg -filters.


Refer to the FFmpeg filters documentation for more information and examples for each filter. This wiki page is for user contributed examples and tips, and contributions to this page are encouraged.

Filter syntax

When documentation refers to "filter options", or says the "filter accepts the following options", the syntax to use for the options is as described in FFmpeg Filters, section 4.1 Filtergraph syntax. Briefly, that syntax is to add, after the name of the filter, an = character, then the name of the first filter option, an = character, and the value of that option. If you want to specify further filter options, you delimit them with :, then append the name of the next filter option, an = character, and the next value.

For instance, to apply the loudnorm filter to an audio stream, the basic syntax is:

ffmpeg -i input -filter:a loudnorm  output

To add the print_format and linear filter options, use the syntax:

ffmpeg -i input -filter:a loudnorm=print_format=summary:linear=true  output

As described in section 4.1 Filtergraph syntax, you can omit the option names and = characters, supplying just the values, delimited by : characters. For example, in this invocation:

ffmpeg -i input -vf scale=iw/2:-1 output

FFmpeg assumes the option names in the order they are declared in the source code. For instance, in this use of the scale filter, FFmpeg assumes the option name width for the value iw/2, and the name height for the value -1.



Starting with something simple. Resize a 640x480 input to a 320x240 output.

ffmpeg -i input -vf scale=iw/2:-1 output

iw is input width. In this example the input width is 640. 640/2 = 320. The -1 tells the scale filter to preserve the aspect ratio of the output, so in this example the scale filter will choose a value of 240. See the FFmpeg documentation for additional information.

Speed up your video

See How to speed up / slow down a video for examples.

Filtergraph,Chain,Filter relationship

What follows the -vf in an ffmpeg command line is a filtergraph description. This filtergraph may contain a number of chains, each of which may contain a number of filters.

Whilst a full filtergraph description can be complicated, it is possible to simplify it for simpler graphs provided ambiguity is avoided.

Remembering that filters in a chain are separated by commas "," chains by a semicolon ";" and that if an input or output is not specified it is assumed to come from the preceding or sent to the following item in the chain.

The following are equivalent:

ffmpeg -i input -vf [in]scale=iw/2:-1[out] output
ffmpeg -i input -vf scale=iw/2:-1 output                                      # the input and output are implied without ambiguity

As are:

ffmpeg -i input -vf [in]yadif=0:0:0[middle];[middle]scale=iw/2:-1[out] output # 2 chains form, one filter per chain, chains linked by the [middle] pad
ffmpeg -i input -vf [in]yadif=0:0:0,scale=iw/2:-1[out] output                 # 1 chain form, with 2 filters in the chain, linking implied
ffmpeg -i input -vf yadif=0:0:0,scale=iw/2:-1  output                         # the input and output are implied without ambiguity

multiple input overlay in 2x2 grid

Here four inputs are filtered together using the -filter_complex option. In this case all of the inputs are the -f lavfi -i testsrc (the testsrc source filter) but could be other inputs.

Within the filtergraph the first input is unchanged, and the other three inputs are individually filtered using hflip, negate, and edgedetect. The hstack and vstack filters are then used to stack each video into the desired location.

ffmpeg -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc -filter_complex \
"[1:v]negate[a]; \
 [2:v]hflip[b]; \
 [3:v]edgedetect[c]; \
 [0:v][a]hstack=inputs=2[top]; \
 [b][c]hstack=inputs=2[bottom]; \
 [top][bottom]vstack=inputs=2[out]" -map "[out]" -c:v ffv1 -t 5 multiple_input_grid.avi

This next example is the same as above, but uses the pad and overlay filters instead. The pad filter is used to make an appropriate sized background, and overlay is used to place each video into the correct location. This method is slower than using hstack + vstack as shown above.

ffmpeg -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc -f lavfi -i testsrc -filter_complex \
"[0:v]pad=iw*2:ih*2[a]; \
 [1:v]negate[b]; \
 [2:v]hflip[c]; \
 [3:v]edgedetect[d]; \
 [a][b]overlay=w[x]; \
 [x][c]overlay=0:h[y]; \
 [y][d]overlay=w:h[out]" -map "[out]" -c:v ffv1 -t 5 multiple_input_grid.avi

Be aware that frames are taken from each input video in timestamp order, so it is a good idea to pass all overlay inputs through a setpts=PTS-STARTPTS filter to have them begin in the same zero timestamp, such as [0:v]hflip,setpts=PTS-STARTPTS[a];[1:v]setpts=PTS-STARTPTS[b];[a][b]overlay.

Escaping characters

As described in the documentation, it can be necessary to escape commas "," that need to appear in some arguments, for example the select filter:

ffmpeg -i input -vf select='eq(pict_type\,I)' -vsync vfr output_%04d.png        # to select only I frames

However an alternative, which also allows for white space within the filtergraph, and which may assist in clarity of reading complex graphs, is to enclose the whole filtergraph within double quotes " " thus:

ffmpeg -i input -vf "select='eq(pict_type,I)'" output       # to select only I frames
ffmpeg -i input -vf "yadif=0:-1:0, scale=iw/2:-1" output    # deinterlace then resize

Note that the examples given in the documentation mix and match the use of "full quoting" and "\" escaping, and that use of unusual shells may upset escaping. See Notes on filtergraph escaping for more information.

Burnt in Timecode

Using the drawtext video filter.

PAL 25 fps non drop frame:

ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\:00': r=25: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4

NTSC 30 fps drop frame

(change the : to a ; before the frame count)_________________________________________________________
ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\;00': r=30: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4

Scripting your command line parameters

If building complex filtergraphs the command line can get very messy so it can help to break things down into manageable pieces. However one needs to be careful when joining them all together to avoid issues due to your shell and escaped characters.

The following example shows a sample bash script containing a filtergraph of one chain with three filters; yadif, scale and drawtext.

# ffmpeg test script



cd $path

filter="yadif=0:-1:0, scale=400:226, drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: \
text='tod- %X':x=(w-text_w)/2:y=H-60 :fontcolor=white :box=1:boxcolor=0x00000000@1"
codec="-vcodec libx264  -pix_fmt yuv420p -b:v 700k -r 25 -maxrate 700k -bufsize 5097k"

command_line=(ffmpeg -i "$in_file" -vf "$filter" "$codec" -an $out_file")

echo "${command_line[@]}"

Note that the filtergraph spans more than one line. The echo command shows the full command as it is executed. Useful for debugging.

The array in the $command_line variable helps avoid loss of the quotes which occurs otherwise. Other shells may behave differently.

Synthetic Input

The testsrc source filter generates a test video pattern showing a color pattern, a scrolling gradient, and a timestamp. This is useful for testing purposes.

This example will create a 10 second output, 30 fps (300 frames total), with a frame size of 1280x720:

ffmpeg -f lavfi -i testsrc=duration=10:size=1280x720:rate=30 output.mpg

ffplay can also be used to view the resulting filtergraph:

ffplay -f lavfi -i "testsrc=duration=10:size=1280x720:rate=30"

You can also specify testsrc as a filter:

ffmpeg -filter_complex testsrc OUTPUT

Another type of testsrc is using the smptebars source filter:

ffmpeg -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30" output.mp4

Or a color

./ffmpeg -f lavfi -i color=c=red:size=100x100

There are other options for generating synthetic video input, see here and here ("generic equation" filter).

Other Filter Examples

Developing your own Filters

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