Linked by Thom Holwerda on Wed 14th Nov 2012 22:12 UTC
Internet Explorer "In Windows 8, we reimagined the browser with IE10. We designed and built IE10 to be the best way to experience the Web on Windows. With the IE10 Release Preview for Windows 7 consumers can now enjoy a fast and fluid Web with the updated IE10 engine on their Windows 7 devices. The release preview of IE10 on Windows 7 is available for download today."
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RE[11]: IE10 still disappointing
by lemur2 on Sat 17th Nov 2012 10:23 UTC in reply to "RE[10]: IE10 still disappointing"
lemur2
Member since:
2007-02-17

How can you have a "higher average bitrate" within the same filesize?

It's like saying you and I both ran a marathon (filesize) in the same amount of time (clip running time), but you went faster.

One average bitrate can't be higher than the other for a clip of the same length and filesize; they are the same.


With VBR, AFAIK the bitrate refers to the video as rendered, not the video as compressed. Because WebM static compression quality per bit is better than h264, and because most video is lower motion rather than higher motion, WebM can deliver a higher (as rendered) bitrate from the same number of as-compressed bits.

As to your other point: so you have no benchmarks (even screenshots?) to support your claim that WebM has higher quality/bitrate than x264? Okie.


Where WebM suffers in terms of objective measurements is in areas of high motion. Because WebM (deliberately) blurs these high dynamic areas, so as not to waste too many as-compressed bits, they compare very poorly between the rendered still frames and the original still frames, and cause WebM to score poorly on objective measures such as PSNR, even though to the human viewers eye when watching the video at normal speed, the blurring of high motion areas has little detrimental (objective) effect on the as perceived quality.

Due mostly to the blurring of high-motion video, a real-life WebM video can easily be objectively measured in terms of YSSM and PSNR as being lower quality than an h264 video, yet still preferred objectively by a human viewer watching the video at normal playing speed. In addition, if you take a still of the same frame during a low-motion scene from WebM and H264, the WebM still frame will be distinctly clearer and sharper, but on some other frame during a high-motion scene, the H264 still frame will be far cleaer and sharper than the WebM one.

So the perceived quality and the measured quality can be quite different.

I did have some screenshots of this which illustrated the point very well, but I can no longer find them. Sorry about that.

I am not, BTW, claiming that WebM is better than H264. I am merely claiming that it performs differently, and for the purposes of video over the web, just as well as h264.

Edited 2012-11-17 10:24 UTC

Reply Parent Score: 1

saynte Member since:
2007-12-10


With VBR, AFAIK the bitrate refers to the video as rendered, not the video as compressed. Because WebM static compression quality per bit is better than h264, and because most video is lower motion rather than higher motion, WebM can deliver a higher (as rendered) bitrate from the same number of as-compressed bits.


That's not what bitrate refers to.

The output bitrate is clearly constant: the number of bits per frame is just bit-depth*width*height (*fps to get bitrate). You don't change the bitdepth and dimensions of your video dynamically, as VBR would imply if it was the "output bitrate" that was being measured.

You wouldn't want your movie bigger and smaller as the bitrate changed.

WebM does not have higher quality/bit(rate), x264 does, and that's EXACTLY what those graphs in the study say.

Additionally the author of x264 has a great breakdown of the WebM/VP8 codec, basically the short side is: it's alright, misses some of the psy features (probably patented, blah) that H264 has.

http://x264dev.multimedia.cx/archives/377

This guy knows his stuff; even implemented a VP8 encoder, so I think his bias, if any, is pretty non-existant.

Reply Parent Score: 3

lemur2 Member since:
2007-02-17

The output bitrate is clearly constant: the number of bits per frame is just bit-depth*width*height (*fps to get bitrate). You don't change the bitdepth and dimensions of your video dynamically, as VBR would imply if it was the "output bitrate" that was being measured.


According to your definition, VBR doesn't exist, and it is not possible to have a video at a certain output bit-depth*width*height*fps with fewer bits.

Your definition is clearly nonsense. Variable Bitrate means the bitrate varies (even though the output bit-depth*width*height*fps does not).

Now if I only need a certain bitrate to get a certain quality for part of a video, and I actually use more bits, then am am using a higher bitrate, and I get better quality as a result. That is how it works, chum. The very graphs you keep referencing say so.

Edited 2012-11-18 07:42 UTC

Reply Parent Score: 2