Some questions about picture quality

[0rion42]

Hello everyone. I'm not quite sure if this is the correct place to post this, but I have a lot of questions that span multiple areas, so here goes.

Recently, I've been reading about getting optimal video quality, particularly using a computer as a media player. I had previously thought that, modern video being digital and all, the choice of player (and video renderer) didn't really make a difference, but am now given to understand that even without having to scale resolutions, different renderers do chroma sampling better than others. In particular, I've read that MadVR is superior to other renderers and yields better final picture quality. So, I had a few questions I was hoping I could get answered:

-Does using a renderer like MadVR actually make a difference in final picture quality? If so, is it significant?

-Do issues like chroma sampling only apply when the video has been ripped (say from a blu-ray) and compressed, or is it a result of the way h264 itself works?

- If different renderers on the computer produce different video quality, does this mean hardware players can also be superior to each other?

-How well does a well set-up HTPC's video quality compare with that of a dedicated player?

-Does resolution scaling occur on the monitor/TV, or within the renderer/hardware player?

-I don't mind getting into some heavier math - is there a good website or textbook that discusses these issues in depth?

If anyone could answer even one of these, I would really appreciate. Thanks very much.

[Warperus]

-Does using a renderer like MadVR actually make a difference in final picture quality? If so, is it significant?Yes, it does. It is noticable sometimes. For me it's like "picture looks different and I like this one more than that one".
Unfortunately, it's not the only issue for PC players/renderers. Some of them simply can't play some files and can't play other files correctly.

-Do issues like chroma sampling only apply when the video has been ripped (say from a blu-ray) and compressedNope, not only ripped. Any interlaced or chroma-unsampled source of any kind can lead to it if you use differennt chroma sampling in encoding.

- If different renderers on the computer produce different video quality, does this mean hardware players can also be superior to each other?Sure, why not?

-Does resolution scaling occur on the monitor/TV, or within the renderer/hardware player?It depends, in general you can expect both to scale resolution. HD-ready TV will scale resolution down to its native one. DVD player can scale resolution of xvid file it's playing. Software player/renderer will generally do the scale, but monitor can work in non-native resolution.

[Asmodian]

I too believe MadVR really does look better, especially after doing color calibration.

It doesn't include the math but I like this site (http://svn.int64.org/viewvc/int64/resamplehq/doc/kernels.html) from PhrostByte to understand the differences between the different resample algorithms.

I think you meant subsampled chroma, chroma-unsampled means B&W right? ;)

Does resolution scaling occur on the monitor/TV, or within the renderer/hardware player?

Depends, it can occur in all those locations and more. Using MadVR it occurs in the renderer but that doesn't mean the video card and the monitor/TV couldn't if they felt like it. Hopefully most equipment doesn't resize if you feed it native resolution RGB but I understand a lot of TVs, for example, will resample RGB to YUV 4:2:2 because they suck.

[Warperus]

chroma-unsampled means B&W right?
I meant 4:4:4 subsampling or RGB source.

[Asmodian]

Wouldn't 4:4:4 or RGB be the only cases where chroma sampling wouldn't be an issue? Assuming the video is at native resolution. The idea of chroma sampling or chroma scaling doesn't work for RGB of course.

-Do issues like chroma sampling only apply when the video has been ripped (say from a blu-ray) and compressed, or is it a result of the way h264 itself works

Blurays are 4:2:0 like almost all consumer sources, except video games, they also suffer from chroma sampling issues. This isn't because of the way H.264 or x264 work but because the U and V (chroma) channels are 1/2 the resolution of the Y (luma) channel in both dimensions as a way to reduce the bandwidth and buffers required for the uncompressed video. H.264 also supports both 4:4:4, the UV the same resolution as Y in both dimensions, and 4:2:2, U and V half resolution horizontally but the same resolution vertically. It also supports RGB which, of course, is the same resolution for all colors.

[Warperus]

Wouldn't 4:4:4 or RGB be the only cases where chroma sampling wouldn't be an issue?
It will be an issue after you use 4:2:0 chroma subsampling in encoding.

[Asmodian]

Ah you are talking about having chroma sampling issues when creating content, such as encoding RGB or 4:4:4 footage to 4:2:0. A common issue people run into when encoding video game footage.

I was thinking about playback, where the choice of renderer is more significant when watching content with subsampled chroma.