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Is there a quality difference Netflix Blu Ray
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El Duderino




Joined: 23 Jan 2011
Posts: 4627
Location: Portland, OR


PostLink    Posted: Thu Jan 21, 2016 1:02 am    Post subject: Reply with quote


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ecrabb wrote:
Yeah, you can do screen grabs, but it would be easier to simply extract the main feature with core audio from both a retail and rental disc and compare the file sizes. If they're both 116 minutes, but one is 13GB and the other 20GB, you know one is much more compressed than the other.


Yes, but you can't show someone a visual IMAGE of how bad or good it is relative. Given the advancements in compression technology, and differences between compression algorithms, smaller file sizes may not tell the whole tale. I'd probably agree that 7GB difference would likely be fairly obvious, IF they we mastered using the same compression technology, but maybe not if they weren't. I wouldn't be surprised to see a compression done in 2015 being smaller with better image fidelity than one from the same movie mastered and compressed using 2001 compression technology.

The following image is like I'm talking about. Full-frame from the frame buffer and losslessy compressed (no cameras / no jpeg, etc) Using such images in an A/B fashion, one can SEE the PQ and even measure the values of pixel triads and contrast, compare, and quantify any differences.

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ecrabb
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Joined: 13 Mar 2006
Posts: 15909
Location: Utah

TV/Projector: JVC RS40, Epson 5010


PostLink    Posted: Thu Jan 21, 2016 4:57 pm    Post subject: Reply with quote

El Duderino wrote:
ecrabb wrote:
Yeah, you can do screen grabs, but it would be easier to simply extract the main feature with core audio from both a retail and rental disc and compare the file sizes. If they're both 116 minutes, but one is 13GB and the other 20GB, you know one is much more compressed than the other.


Yes, but you can't show someone a visual IMAGE of how bad or good it is relative. Given the advancements in compression technology, and differences between compression algorithms, smaller file sizes may not tell the whole tale. I'd probably agree that 7GB difference would likely be fairly obvious, IF they we mastered using the same compression technology, but maybe not if they weren't. I wouldn't be surprised to see a compression done in 2015 being smaller with better image fidelity than one from the same movie mastered and compressed using 2001 compression technology.


Yes, compression is better now than it was 15 years ago, but only within the confines of the codec in question. Are there better compression engines now than there were in 2001? Of course, but h.264 is only so good. Will the difference be night/day? No. Could the image quality be better now at slightly lower data rates compared to 10 years ago? Likely, but again - looking at frame grabs only tells part of the story. It's a moving image. Pixel-peeking a still image that's on-screen for 0.042 seconds is only worth so much.

Regardless, this thread was about comparing new retail vs. new rental releases, so I don't see how discussing advancements to compression technology is really germane to the discussion. The reason I mentioned comparing file-sizes wasn't to evaluate the relative quality of the video. Obviously that's not possible, though it's quite safe to say that between two files authored around the same time, if one is significantly smaller, it will be of lower quality. Anyway, I suggested comparing file sizes merely as a quick method of determining whether the two releases were significantly different. It's not much of a leap the to assume the smaller file is of lower-quality.

Maybe I'll see if I can pick up a Redbox this weekend of something I bought recently and we'll see if there's any difference and how much. It would be interesting for sure.

It would be fun to throw an Apple iTunes and Vudu frames into the mix, but I don't have a good way to capture a clean digital frame grab uncompressed.

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El Duderino




Joined: 23 Jan 2011
Posts: 4627
Location: Portland, OR


PostLink    Posted: Thu Jan 21, 2016 11:45 pm    Post subject: Reply with quote

ecrabb wrote:
It would be fun to throw an Apple iTunes and Vudu frames into the mix, but I don't have a good way to capture a clean digital frame grab uncompressed.


I dunno what you're using (AppleTV/Roku/ChromeCast/Fire?), but it can be surprising what the [Alt]PrtScr key can capture on a HTPC. I thought I'd try it with YouTube full screen and it captured it just fine.
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