fix: respect the user's max_width setting for the built-in video previewer

[ze0987]

Currently, Yazi only scales thumbnails to preview.max_height, which means that thumbnails of videos in landscape orientation are unnecessarily large.

Example:

max_width       = 600
max_height      = 900
image_quality   = 75

Before

File size: 131 kB
Image size: 1600x900
On the left is a preview in Yazi, and on the right is a generated thumbnail.

After

File size: 28 kB
Image size: 600x338

[sxyazi]

Thanks for the PR!

Could you provide some benchmarks to see how this change affects performance — separately when the video size is under max_width/max_height and when it reaches them?

[ze0987]

Sure.

max_width       = 600
max_height      = 900
image_quality   = 75

Video resolution 320x180, software

Before

  Time (mean ± σ):     253.2 ms ±   1.7 ms    [User: 194.5 ms, System: 53.8 ms]
  Range (min … max):   250.8 ms … 255.5 ms    10 runs

After

  Time (mean ± σ):     254.1 ms ±   1.6 ms    [User: 194.9 ms, System: 54.5 ms]
  Range (min … max):   251.3 ms … 256.3 ms    10 runs

Video resolution 320x180, vaapi

Before

  Time (mean ± σ):     272.6 ms ±   2.4 ms    [User: 198.1 ms, System: 68.9 ms]
  Range (min … max):   269.8 ms … 277.5 ms    10 runs

After

  Time (mean ± σ):     278.0 ms ±   2.7 ms    [User: 202.2 ms, System: 70.4 ms]
  Range (min … max):   273.3 ms … 282.8 ms    10 runs

Video resolution 1920x1080, software

Before

  Time (mean ± σ):     884.0 ms ±   2.7 ms    [User: 778.3 ms, System: 95.8 ms]
  Range (min … max):   879.6 ms … 888.7 ms    10 runs

After

  Time (mean ± σ):     843.4 ms ±   2.9 ms    [User: 744.5 ms, System: 89.7 ms]
  Range (min … max):   838.7 ms … 846.9 ms    10 runs

Video resolution 1920x1080, vaapi

Before

  Time (mean ± σ):     448.4 ms ±   3.7 ms    [User: 314.1 ms, System: 126.7 ms]
  Range (min … max):   442.9 ms … 453.8 ms    10 runs

After

  Time (mean ± σ):     388.1 ms ±   2.9 ms    [User: 268.0 ms, System: 113.2 ms]
  Range (min … max):   383.8 ms … 392.5 ms    10 runs

With this PR, thumbnails of videos smaller than preview.max_width x preview.max_height will be upscaled to preview.max_width x preview.max_height, which may or may not be a good thing.

[maga-tama]

This one won't upscale https://superuser.com/a/794924
"-filter_complex", string.format("scale=iw*min(1\,min(%d/iw\, %d/ih)):-1:flags=fast_bilinear", rt.preview.max_width, rt.preview.max_height)

[ze0987]

Here is another variant:

"-vf", string.format("scale='min(%d,iw)':'min(%d,ih)':force_original_aspect_ratio=decrease:flags=fast_bilinear", rt.preview.max_width , rt.preview.max_height),

But the question remains, upscale or not? Both approaches have their pros and cons. Or maybe give the users a switch and let them decide. The performance difference is small.

max_width       = 600
max_height      = 900
image_quality   = 75

Single Intel E-core @ 800 MHz

2160p vaapi

Test	Mean [s]	Min [s]	Max [s]	Relative
main	3.292 ± 0.005	3.284	3.298	1.03 ± 0.00
upscale	3.197 ± 0.009	3.181	3.208	1.00 ± 0.00
scale='min(%d,iw)':'min(%d,ih)	3.195 ± 0.004	3.189	3.199	1.00
scale=iw*min(1\,min(%d/iw\, %d/ih))	3.198 ± 0.006	3.186	3.205	1.00 ± 0.00

180p vaapi

Test	Mean [ms]	Min [ms]	Max [ms]	Relative
main	276.5 ± 2.6	272.8	280.2	1.00
upscale	283.6 ± 3.3	278.1	287.5	1.03 ± 0.02
scale='min(%d,iw)':'min(%d,ih)	276.6 ± 3.2	270.2	281.4	1.00 ± 0.01
scale=iw*min(1\,min(%d/iw\, %d/ih))	278.6 ± 2.5	275.5	283.7	1.01 ± 0.01

[maga-tama]

Or maybe give the users a switch and let them decide.

Feels like the right call.
Even though it's just for video, I can still think of cases it'll get real old real fast -
short clips/reactions/memes (or just saving as videos instead of gifs in general)

[sxyazi]

Thanks for the benchmarks, it's really helpful!

I decided to use scale='min(%d,iw)':'min(%d,ih)' to keep the old behavior here

[sxyazi]

Thank you!