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Comment by Youden | Hacker News Reader

> Blu-ray quality is better than streaming in some cases.

The wording here sounded a bit off to me here; I read it as "usually Blu-ray quality is worse or the same as streaming quality but sometimes it's better" while I think what you probably meant (and would make a lot more sense) was "usually streaming is just as good as Blu-ray but sometimes the streaming quality is bad and a Blu-ray is better".

Is the latter what you meant?

Though there is also the possibility that there's a 4K version of a movie available to stream but not released on Blu-ray. Maybe that's what you referred to?

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Blu Ray quality is always better than streaming, by an order of magnitude. Blu Ray 4k has a bitrate of between 92 and 144Mb/s[1], Netflix bitrate at 4K is around 16Mb/s[2] - the resolution is the same but online streaming platforms will need to use loads of compression or most of their user base would not have a fast enough connection to watch video in 4K.

Full HD 1080p bitrates are a similar story, Blu Ray is much higher than streaming (36Mb/s vs around 6Mb/s, respectively)[3][4].

[1] https://en.wikipedia.org/wiki/Ultra_HD_Blu-ray

[2] https://big-photography.com/guides/what-is-netflix-4k-bitrat...

[3] https://en.wikipedia.org/wiki/Blu-ray#Bit_rate

[4] https://www.howtogeek.com/338983/how-much-data-does-netflix-...

You're right of course that given the same resolution, a Blu-ray will have a higher bitrate but to elaborate on what I was saying:

- The perceived streaming quality may match Blu-ray because the bitrate is high enough that humans can't tell the difference anymore. This is especially likely to be the case is the content isn't challenging.

- The perceived quality may be higher than Blu-Ray because 4K is available for streaming but not as a Blu-Ray release. So the comparison isn't 1080p streaming vs. 1080p Blu-ray but 4K streaming vs. 1080p Blu-ray. If you plot perceived quality vs. bitrate against each other for multiple resolutions, you usually find that it makes sense to increase resolution at lower bitrates than you might expect. I'd honestly expect that 16Mb/s 4K would look better to viewers than 40Mb/s 1080p. Plus, 4K is usually encoded using a more modern and efficient codec than the ancient ones we use for 1080p Blu-ray.

But note that I'm talking about perceived quality here. Higher bitrates might lead to higher computed quality metrics like PSNR and SSIM but past a point, those metrics no longer have any correlation to human perception and that point is lower than you might think.

I get your point, just to play devil's advocate though: up until a few years ago, there was an often repeated argument that "the human eye can't see more than 30fps" (it was used to justify the fact that many console games were capped at 30fps back then)... Today, many gamers use a 144hz monitor and would never go back to a lower refresh rate.

I wonder if the same story will happen with regards to lossy video compression, I mean perhaps, once our tech will be so much better that we will be able to use lossless formats for video, people will look back at the formats we have today and think that they look bad.

Remember VHS? I used to think they looked alright back then :-)

I think that the lower adoption of Blu Ray vs. streaming is purely due to convenience, not quality. Most people don't want to deal with physical media. In the same way that uncompressed audio is better than Spotify and similar services, yet almost no one buys audio CDs any more.

In Audio, there are now services that let you download uncompressed and/or lossless audio (Bandcamp, Beatport etc.), they are not as mainstream as Spotify but they are moderately successful and have their place in the market.

I wonder if the same thing could happen for movies: offering higher quality downloadable movies, without the physical medium. Perhaps cinephiles could be interested. Maybe it will happen when average bandwidth, at least in the developed world, approaches the equivalent of a 4K Blu Ray bitrate: no one wants to wait for a long download to end, people want just-in-time streaming.

(Note: Blu Ray, unlike Audio CD, is not lossless, it's just that it's got much less compression than the typical streaming services).

I don't think the claim that the human eye can't see more than 30fps was ever supported by evidence, it was just "common knowledge" like other falsehoods such as certain parts of the tongue only detecting certain tastes. I think it was actually based on the minimum frame rate necessary for a human to perceive motion instead of a slide show. Scientifically, a quick Google indicates that humans can see up to around 90Hz for more normal cases and 500Hz for a specific edge-case [0].

When it comes to video compression though, industry practice is largely based on the result of user testing. There are well-controlled tests where a bunch of people are put in a specific test environment and shown videos encoded using different parameters and there are larger scale A/B tests where a streaming platform will tweak parameters and see how they affect metrics like time spent consuming content. So I'm confident that the compression of today matches the users and hardware of today.

However hardware can change and I expect that's what will drive increases in video quality. For example the encodes of today are biases to some extent by the fact that people watch videos on tiny screens like phones or tablets, which are likely a bottleneck for quality perception. If people start consuming more content on say VR headsets, streaming platforms may see the need to increase quality. 8K is also a possible driver (especially for very large displays).

Connectivity is also a big deal. Lossless music is possible because the bitrate is relatively low but streaming 4K blu-ray is out of the question for many people at the moment. In the future though it's definitely a possibility.

[0]: https://www.nature.com/articles/srep07861

Yes I mostly meant the latter but like you said, occasionally there are 4k streaming versions when there is only 1080p on blu-ray. Most of the time I don't feel the 4k versions are that much better looking though.

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