Webp Lossless: 0 and 1, What's the difference?

[Jay123210599]

All right, I decided to stick with image formats that are compatible with most browsers (pngs, webps, jpgs, and possibly bmps). For these 6 images, I used webp lossless 0 for 3 images and lossless 1 for the other 3. Can somebody tell the difference?

[Selur]

yes, without zooming in:
https://imgsli.com/MjM0MTgz look at the gray texture under the letters in the front
https://imgsli.com/MjM0MTg0 look at the gray texture in the upper left corner
https://imgsli.com/MjM0MTg1 look at the gray texture in the upper left corner
if you zoom in, you can clearly see more artifacts around the lines.

Cu Selur

[Jay123210599]

yes, without zooming in:
https://imgsli.com/MjM0MTgz look at the gray texture under the letters in the front
https://imgsli.com/MjM0MTg0 look at the gray texture in the upper left corner
https://imgsli.com/MjM0MTg1 look at the gray texture in the upper left corner
if you zoom in, you can clearly see more artifacts around the lines.

Cu Selur

Let me guess, the ones with lossless 1 are better? Well for 0, I got this: "[libwebp @ 0000028d0922f700] Using libwebp for RGB-to-YUV conversion. You may want to consider passing in YUV instead for lossy encoding." How do I fix that?

[Selur]

Sorry, I'm no fortune-teller who could guess what you are talking about.
If you use ffmpeg, looking at https://ffmpeg.org/pipermail/ffmpeg-cvslog/2015-May/089956.html seems to indicate that this just a notice/warning which wants to help. So depending on what you want to do, there is nothing to fix.

Let me guess, the ones with lossless 1 are better?

Can't help you if you can't figure that out yourself.

[poisondeathray]

Well for 0, I got this: "[libwebp @ 0000028d0922f700] Using libwebp for RGB-to-YUV conversion. You may want to consider passing in YUV instead for lossy encoding." How do I fix that?

You control the RGB to YUV conversion - especially the matrix - perhaps other parameters (depends on the video) . e.g using zscale. That was explained in another thread .

Same with going from YUV video to lossless webp (which is RGBA only) - you will get wrong colors if the wrong parameters are used, or ffmpeg "guesses" incorrectly

And there is no way to do it automatically and correctly for every video or image, because there are too many possible combinations and types of input/outputs. Many source videos are flagged improperly or not flagged at all. You need to specify the extra parameters (not just for webp, but for every conversion), or "hope" that ffmpeg guesses it right

[Jay123210599]

Well for 0, I got this: "[libwebp @ 0000028d0922f700] Using libwebp for RGB-to-YUV conversion. You may want to consider passing in YUV instead for lossy encoding." How do I fix that?

You control the RGB to YUV conversion - especially the matrix - perhaps other parameters (depends on the video) . e.g using zscale. That was explained in another thread .

Same with going from YUV video to lossless webp (which is RGBA only) - you will get wrong colors if the wrong parameters are used, or ffmpeg "guesses" incorrectly

And there is no way to do it automatically and correctly for every video or image, because there are too many possible combinations and types of input/outputs. Many source videos are flagged improperly or not flagged at all. You need to specify the extra parameters (not just for webp, but for every conversion), or "hope" that ffmpeg guesses it right

So lossless webp isn't suited for YUV videos? I also checked and webp probably doesn't work YUV 422 or 444 at all, huh? So how do I set the compression rate for png files? Can ffmpeg make zip/7z/rar/zqad files?

[poisondeathray]

So lossless webp isn't suited for YUV videos? I also checked and webp probably doesn't work YUV 422 or 444 at all, huh?

Lossless webp is RGBA only .

Lossy webp is YUV 4:2:0 only

When you are posting an image to display for a website , typically it will be converted to 8bit RGB anyways. Lossless webp will always produce smaller filesizes than the highest compression png . The main negative for webp is lower compatibility - a legacy browser won't support webp, and slower decoding times. All modern browsers support webp by default (native support)

I'm just repeating myself - go back and look at the other threads for full explanation and examples

So how do I set the compression rate for png files?

It's already been explained numerous times in your threads . Go back and look.

[Jay123210599]

So lossless webp isn't suited for YUV videos? I also checked and webp probably doesn't work YUV 422 or 444 at all, huh?

Lossless webp is RGBA only .

Lossy webp is YUV 4:2:0 only

When you are posting an image to display for a website , typically it will be converted to 8bit RGB anyways. Lossless webp will always produce smaller filesizes than the highest compression png . The main negative for webp is lower compatibility - a legacy browser won't support webp, and slower decoding times. All modern browsers support webp by default (native support)

I'm just repeating myself - go back and look at the other threads for full explanation and examples

So how do I set the compression rate for png files?

It's already been explained numerous times in your threads . Go back and look.

So it will still turn out lossy for webp files? Also, I found that jpeg 2000 supports all kinds of YUV.

[poisondeathray]

So it will still turn out lossy for webp files?

Already answered in your other posts. I'll repeat it for the 3rd time

Technically lossy yes, same with PNG . YUV to RGB is lossy unless the RGB is in float precision . You can never get back the original YUV values with integer RGB, that is defined as loss

You get negative RGB values and values > 255 in 8bit , or > 1023 in 10bit - which get clipped = quality loss . Float RGB keeps those negative values and values greater than 255 . On a scale of 0-1 , float keeps negative values and values >1.

You also get rounding errors and precision loss for typical RGB conversion . 16bit RGB PNG is still lossy in terms of the original YUV values . Also when you chroma upsample video to RGB, that can be lossy and non reversible too, unless you use nearest neighbor

***But it doesn't matter for images posted to a website, because most people are viewing on a 8bit RGB display anyways. Even when you watch video directly, you're not watching YUV directly , you're watching an RGB converted representation . Displays work in RGB

Also, I mean for ffmpeg when making png files.

Yes, answered many times , and other programs that make smaller pngs than ffmpeg were given

[Jay123210599]

Also, I mean for ffmpeg when making png files.

[/QUOTE]Yes, answered many times , and other programs that make smaller pngs than ffmpeg were given[/QUOTE]

I was only given optimizers, not actual programs that make image sequences from videos.

[Jay123210599]

https://forum.videohelp.com/threads/413007-Smallest-PNG-File-Size
https://forum.videohelp.com/threads/413075-Smallest-PNG-File-Size-Part-2

[poisondeathray]

I was only given optimizers, not actual programs that make image sequences from videos.

ffmpeg is an actual program that can make image sequences from videos.

Options were given in ffmpeg to reduce the file size. There is a tradeoff between speed and filesize, as always


Use the optimizers on the ffmpeg exported exported sequences to reduce them farther, or live with the current filesize. The optimizers have speed vs. compression ratio tradeoff too. At the highest compression it might take minutes per frame


You decide on a tradeoff between processing time, vs. compression ratio, workflow ease .