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Old 26th September 2017, 01:59   #661  |  Link
x265_Project
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Quote:
Originally Posted by IgorC View Post
x265_Project, you aren't an average forum member. This is serious stuff. You're developer and You've lied about 2.4x efficiency of HEVC over JPEG and lately have tried cherrypicking on results.
You're free to disagree with me, but it's another thing to call me a lier, even if you tried to soften the blow with a smiley face. I haven't lied about anything. If you want people to respond to you on a public forum like this, you need to stick to the subject (the technology), and avoid personal accusations or insults.

It's not "cherrypicking" to point out that there is a place along the RD curve where the efficiency gain of one codec is 2x or greater than another codec. That's the way RD curves work. That's why I pointed out that " the % improvement in compression efficiency varies depending on ... the quality levels being compared." Pick a different place along the 2 curves (as you tried to), and you'll see a different gain.

It's not possible quantify the efficiency gain of Codec A over Codec B in with perfect precision and get universal agreement, because the result always depends on the content, the settings (like Chroma subsampling), and the PLACE ON THE RD CURVEs (the quality level) you choose in your test. Change any variable, and you'll get a different result (especially the place on the RD curve that you're attempting to compare).

The only place along the RD curve that no one can debate is the highest quality - lossless compression. Certainly the % bit rate savings will be different for lossless quality than for typical lossy compression settings. But that doesn't mean that it isn't valid to say that "for typical lossy compression bit rates the savings is X". We could argue ad infinitum as to what bit rates are typical (what point on the RD curve we should compare). But that would be a pissing contest.

We're discussing/debating a very limited set of data from a couple of studies that are several years old, using small picture sizes (800x1280). To add more clarity and arrive at a consensus we need more data, using a wider range of content, picture sizes and quality levels, as well as the latest builds of HEVC encoders (x265, HM reference encoder, etc.).
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Old 26th September 2017, 06:20   #662  |  Link
littlepox
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Another concern would be regarding the wording.
If I have 10 apples and you have 24, can you claim that you have 2.4x more apples than me?

To me, even "On average, JPEG requires a bit rate that is 139% higher (2.39x) than HEVC to achieve identical quality to HEVC Intra compression. I rounded this to 2.4x. " is true, I can only conclude HEVC is 1.39x(or 1.4x) more efficient than JPEG.

Alternatively, I can conclude HEVC is 2.39x(or 2.4x) as efficienct as JPEG.

I know that people often use them in a very confusing way, but from the point of rigorous mathematics, when you use "more than" after a quantity, you need to do minus.

Last edited by littlepox; 26th September 2017 at 06:37.
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Old 26th September 2017, 10:43   #663  |  Link
Jamaika
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This is just a matter of codecs advertising. The truth is that HEIF images aren't implemented ie BPG or HEIF. Producers favor weaker processors for JPEG processing.
What about converting mjpeg movies to YUV? It is a tragedy and it's good that the codec comes out of the outlet. Despite the recommendations, it's better to do it with RGB.

source --> mjpeg(yuv422p10bit)(higer quality) --> x264(yuv422p10bit)
source --> RGB --> x264(yuv422p10bit)


PS I haven't convinced the PSNR or other metrics. VMAF advertising is also only available on paper.
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Old 26th September 2017, 15:13   #664  |  Link
x265_Project
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Quote:
Originally Posted by littlepox View Post
Another concern would be regarding the wording.
If I have 10 apples and you have 24, can you claim that you have 2.4x more apples than me?

To me, even "On average, JPEG requires a bit rate that is 139% higher (2.39x) than HEVC to achieve identical quality to HEVC Intra compression. I rounded this to 2.4x. " is true, I can only conclude HEVC is 1.39x(or 1.4x) more efficient than JPEG.

Alternatively, I can conclude HEVC is 2.39x(or 2.4x) as efficienct as JPEG.

I know that people often use them in a very confusing way, but from the point of rigorous mathematics, when you use "more than" after a quantity, you need to do minus.
Good point.
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