SD into HD
Upscale and pillar-box a SD video file into a HD video file.
-i input_file \
-c:a copy \
- starts the command
- -i input_file
- path, name and extension of the input file
- -filter:v "colormatrix=bt601:bt709, scale=1440:1080:flags=lanczos, pad=1920:1080:240:0"
- set colour matrix, video scaling and padding
- -c:a copy
- re-encodes using the same audio codec
- path, name and extension of the output file
We consider here a SD video file having square pixels. 1440 x 1080 pixel is the maximal size in 4:3 aspect ratio fitting into the 1920 x 1080 pixel of HD.
Upscaling – including from SD to HD – does never increase the quality of the image. At best it’s the same quality.
The video filter is specified by
-filter:v. We advise to avoid the alias
-vfilter and its abbreviation
-vf as well. The quotation marks are not mandatory for these video filters, yet we advice to put multiple filters into quotation marks. The quotation marks allow to insert a space between the filters for readability.
The luma coefficients are modified from SD video (according to Rec. 601) to HD video (according to Rec. 709) by a colour matrix. Note that today Rec. 709 is often used also for SD and you may cancel this parameter.
Note that the
"scale=1440:1080" filter works for both upscaling and downscaling. Therefore this filter applies also e.g. for transforming a 2K scan of a 4:3 film into a HD format for post-production and/or dissemination purposes. We use the Lanczos scaling algorithm (
flags=lanczos), which is slower but gives better results than the default bilinear algorithm.
pad=1920:1080:240:0 gives bit by bit exactly the same result if expressed as
pad=1920:1080:(ow-iw)/2:(oh-ih)/2 by using relative values for input width (iw), input height (ih), output width (ow) and output height (oh).
The audio codec is specified by
-codec:audio, which may be abbreviated as
-c:audio). We advise to avoid the alias
-acodec. For silent videos you can replace
-c:a copy by
-an; for video with sound you may choose to re-encode with another audio codec which is allowed by the container.