Note how the resize comes before the codec setting. Of course, you won't necessarily use that many (or even any) options depending on the filters you choose.Ī simple resize and convert to ProRes 422HQ would be:įfmpeg -i "inputvideo.mp4" -vf "scale=1280:720:flags=spline" -c:v prores -profile:v 3 -pix_fmt yuv422p10le -c:a pcm_s16le "outputvideo.mov" vf "filter1=optiona:optionb:optionc, filter2=optiona:optionb:optionc" vf has so many filters it would be impossible to describe here, but the structure for how each is called is basically: Q3: What variant of Lanczos is used in default lanczos from scale and zscale? Are these both Lanczos3? The number of taps for Lanczos3 can be defined as 3 or 6 ( source1, source2).Resizing in FFMPEG is done via filters, which are specified by the -vf switch. Q2: The descriptions of param0 and param_aare a little different - do these parameters define same thing? Q1: Are there any important differences between scale and zscale in terms of quality? Which one could be better to use to downscale the video? Lanczos can use additional parameter here: param_a is defined as "the number of filter taps", I don't know its default value. Lanczos can use additional parameter here: param0 is defined as "the width (alpha)", its default value is 3.įFmpeg can use zscale with lanczos, spline16 and spline36 parameters. Variants of the algorithm are defined by "the number of filter taps".įFmpeg can use scale/ sws_flags with lanczos and spline parameters. Spline ( documentation), it has a few variants: Spline16, Spline36 (and others) Lanczos ( documentation), it has a few variants: Lanczos3, Lanczos4 (and others) There are two filters best to downscale the video ( source): Note: I've read that -sws_flags method can be sometimes buggy ( source) and in these cases FFmpeg will use its default filter, not the selected one. There are three main methods with these options to select resize filter:
It looks like scale is the default scaler and zscale requires additional library to enable it. There are two main options to scale the video in FFmpeg: scale ( documentation) and zscale ( documentation).
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