Useful Ffmpeg Filters.

This is covering other things that can be done directly in ffmpeg that might be useful.

Table of contents

Useful Ffmpeg Filters.

Other FFmpeg Resources

GOP values explained
ffimprovisr is a great resource to find more friendly descriptions/examples of common ffmpeg use-cases.

Audio

-filter_complex "[1:0]apad" -shortest

This is a useful filter to add when adding an audio file, if the audio file might not match the length of the resulting movie. This will either pad the audio to match the video, if the audio is short, or truncate the audio to match the video.

TODO - Provide full example of adding audio to the “quickstart” demo.

Image resizing.

Keeping the image height a factor of 2.

There may be reasons that you want to do any image resizing directly inside ffmpeg, (e.g. when converting from another movie format). A number of the codecs require that the width and height be a factor of 2 (and sometimes 4). The expression below will ensure that the height is set correctly, assuming the width is 1920

-vf scale=1920:trunc(ow/a/2)*2:flags=lanczos

If you are downrezing, you will get the best results with the lancozs filter, otherwise the default is bicubic.

TODO - this needs testing, to confirm filter quality.

See: https://trac.ffmpeg.org/wiki/Scaling for more info.

Concatination of video files.

See: https://trac.ffmpeg.org/wiki/Concatenate

This has been useful in splitting long prores encodes into chunks, and then merging them back together. The merge process is not quick, so there are limits to how much you can split the process, but provided that the merge process not I/O bound, it can typically end up with faster encodes.

TODO - Provide some examples of speed improvement, as well as a sample command line.

ffmpeg help


ffmpeg -formats	list all file formats
ffmpeg -muxers	list all muxers (e.g. mp4, mov)
ffmpeg -h muxer=	List of options for a particular muxer, e.g. ffmpeg -h muxer=mp4
ffmpeg -filters	list all filters
ffmpeg -codecs	list all codecs (encoders and decoders)
ffmpeg -encoders	list just encoders
ffmpeg -h encoder=	List args for specified encoder, e.g. ffmpeg -h encoder=prores_ks. This also lists what supported pixel formats are supported.
ffmpeg -h decoder=	List args for specified decoder, e.g. ffmpeg -h decoder=exr

Useful Filters

Ffmpeg has a crazy number of filters (see Ffmpeg filters) below are some potentially relevant ones to VFX pipelines.

stereo framepack

https://www.ffmpeg.org/ffmpeg-filters.html#toc-framepack - Generate a frame packed stereoscopic video

ffmpeg -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT

stereo3d

https://www.ffmpeg.org/ffmpeg-filters.html#toc-stereo3d Re-pack an existing stereo movie into a different format

SMPTE HD bars

Creates a SMPTE HD colorbars image. NOTE, this is actually created in YUV space, and only for 8-bit Y’CrCb.

ffmpeg does have a built-in SMPTE color bars, however by default, it does not create it in the right colorspace, so you do need to specify the color primaries, colorspace and colortrc to make it behave correctly. Also note, these are 8-bit only.

This is an h264 output yuv422p

ffmpeg -re -color_primaries bt709 -colorspace bt709 -color_range tv -color_trc bt709 -f lavfi -i smptehdbars=duration=1:size=1920x1080:rate=1 -c:v h264 -crf 10  smptehdbars-h264.mov

This is a 8-bit 444 raw encode.

ffmpeg -re -color_primaries bt709 -colorspace bt709 -color_range tv -color_trc bt709 -f lavfi -i smptehdbars=duration=1:size=1920x1080:rate=1,format=yuv444p -c:v v408 smptehdbars-v408.mov

This is a PNG output, warning this would only be to the legal range, so the pluge would be zeroed out:

ffmpeg -color_primaries bt709 -colorspace bt709 -color_trc bt709 -re -f lavfi -i smptehdbars=duration=1:size=1920x1080:rate=1 -vframes 1  smptehdbars.png

Zoneplate

Creates a Zoneplate test chart. This was introduced in ffmpeg 6.1 and is great for testing filtering.

Creating it with ffmpeg directly to RGB:

ffmpeg -f lavfi -i zoneplate=ku=512:kv=100:kt2=0:ky2=256:kx2=556:s=wvga:yo=0:kt=11:duration=1 -pix_fmt rgb48be zoneplate_rgb16.png

Creating it with ffmpeg directly to YCrCb:

ffmpeg -f lavfi -i zoneplate=ku=512:kv=100:kt2=0:ky2=256:kx2=556:s=wvga:yo=0:kt=11:duration=1 -pix_fmt yuv420p10 -strict -1 zoneplate_yuv420p10.y4m

Nullsrc

A dummy source video signal.

Creating a blank YUV h264 file of 1024 frames.

ffmpeg -r 24 -f lavfi -i nullsrc=s=1280x720,format=yuv444p -frames:v 1024 yuv444p.mov

Creating a blank YUV 10-bit h264 file

ffmpeg -r 24 -f lavfi -i nullsrc=s=1280x720,format=yuv444p10le -frames:v 1024 yuv444p10le.mov

THis is commonly used with geq.

geq

geq Apply a generic equation to each pixel

ffmpeg -r 24 -f lavfi -i nullsrc=s=512x512 -pix_fmt yuv444p -frames:v 1024 -vf geq=X/2:128:128 yuv444p_ramp.mov

If you want other bit-depths, you do need to add an additional format flag for example:

ffmpeg -r 24 -f lavfi -i nullsrc=s=1024x512,format=yuv444p10le -frames:v 1024 -vf geq=X:512:512 yuv444p10_ramp.mov

identity

Calculate the differences between two image streams. toc-identity

ffmpeg -i movie1.mov -i movie2.mov -lavfi identity -f null -

Will output a line like:

 identity Y:0.430940 U:0.516449 V:0.448389 average:0.465259 min:0.452062 max:0.480941``

Where each number is a 0-1 scale, where 1 is identical.

The two images need to be the same resolution and pixel format (at least both RGB or YCrCb).

lut lutrgb and lutyuv

lut_002c-lutrgb_002c-lutyuv

Allows you to create a calculated LUT that is then applied to the picture.

PSNR

Obtain the average, maximum and minimum PSNR (Peak Signal to Noise Ratio) between two input videos psnr

ffmpeg -i movie1.mov -i movie2.mov -lavfi psnr -f null -