Comments on: R-D Performance of 1/8-pel MCP on HD Sequences

By: Carlos

Carlos — Mon, 14 Sep 2009 09:18:14 +0000

Many thanks for your reply.

Yes, more bits are required to represent the higher precision MVs, but is that possible to have a situation like the “Station” sequence that having a 16.15% bitrate increase? Since it is only one bit per motion vector.

I read some comment from the Internet that suggest that it may be due to the mismatch of SATD(or SAD) used in MV search with the SSD used in RDO, how do you think about that?

By: Jie Dong

Jie Dong — Mon, 14 Sep 2009 07:42:40 +0000

MV’s resolution is increased, which means that more bits are needed to represent the same displacement, compared with 1/4-pixel MCP.

By: Carlos

Carlos — Mon, 14 Sep 2009 03:40:55 +0000

Your result is compared to the “anchor” configuration, right?

I’m curious that why there is negative effect of using 1/8-pel MCP compared to 1/4-pel, since 1/8-pel MCP just search more sub-positions. I think the result should be “same or better”, no matter how bad are the 1/8-pel sub-positions interpolated.

Any ideas or hints?

By: Mihai Moise

Mihai Moise — Thu, 25 Jun 2009 04:02:44 +0000

Images have order-3 patterns. A better way of doing interpolation at 1/8-pixel sub positions would be to fit a 3rd-order polynomial through the 4 neighboring pixels on the same line, then use the polynomial to interpolate.

By: Mack

Mack — Fri, 12 Jun 2009 08:12:06 +0000

Optimizing an algorithm for PSNR will deprive output quality of what it could’ve had if it was optimized for something like SSIM. I haven’t checked out VQM but it’s cool as long as they take the step up from PSNR. It is NOT consistent for perceived quality in my experience.

By: Jie Dong

Jie Dong — Mon, 08 Jun 2009 11:29:34 +0000

Yes. PSNR has some problems. But in the framework of hybrid video coding, where distortion is caused by quantization in the transform domain, PSNR correlates well with the perceived quality, although not strictly increasing with it.

The experiment herein follows the test condition and the evaluation criterion specified by VCEG. Now, VCEG is considering using VQM to evaluate the subjective quality. But I think PSNR will be relevant in quality measurement for quite a long time.

By: Mack

Mack — Mon, 08 Jun 2009 08:30:47 +0000

Why measure quality with PSNR? That metric blows.