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Author Topic: 4K question?  (Read 955 times)

bob.gas

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Re: 4K question?
« Reply #15 on: January 10, 2020, 03:02:23 PM »

Interestin Alex thanks.
I'ts probably about 10 years ago i read the article  ;D
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Alex Atkin UK

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Re: 4K question?
« Reply #16 on: January 11, 2020, 02:40:42 AM »

Interestin Alex thanks.
I'ts probably about 10 years ago i read the article  ;D

One thing I forgot to clarify is HOW a channel broadcasts is a night/day difference.

The same way Netflix maximise their bitrates, if you spend the money/effort to tweak every last settings and use really CPU intensive encoding, you can really squeeze amazing quality into so so bitrates, to some extent.

There were one or two channels on Sky which pre-encoded their feed and looked absolutely astonishing despite having a relatively low bitrate.

Most channels use real-time encoders which by their nature can never be particularly efficient.  The movie and sports channels as I recall they try to balance the actions in the content, as they can put things side by side on the same mux and have them "borrow" bitrate from each other.  If you can coincide the action in one movie to be a quiet part in another, you use the bandwidth more efficiently.  Its clever, but really highlights how they try to get blood out of a stone.
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sevenlayermuddle

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Re: 4K question?
« Reply #17 on: January 11, 2020, 09:41:00 AM »

Bottom line for me is my Netflix HD is, subjectively, usually pretty awful with blatantly obvious compression artefacts.  If I were to rank it out of 10 I’d give it about a 3, whereas BBC1 HD on Freeview I’d give a 6.   On my HD Apple TV,  I’d give regular iTunes movies an 8, with Apple TV+ getting a 9+.

Then again, I only pay for Netflix HD at the moment as, last time I looked, their 4K seemed to be largely restricted to their own home made series, that I rarely watch.   As suggested earlier about a different service, I wonder if it might be a policy decision to allow HD to look bad, in order to make 4K look better? 

I only noticed yesterday, if I touch the ‘info’ button in my TV remote it shows me the bitrate and resolution.   The bit rate is static, does not fluctuate, so I guess it is an average.   Watching a 2017  movie in HD, it showed 4.6 Mbps all the way through.
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Alex Atkin UK

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Re: 4K question?
« Reply #18 on: January 11, 2020, 02:39:45 PM »

That's curious because my TV is OLED and shows up artefacts VERY clearly, especially as I tend to leave HDR Effect turned on which expands the contrast ratio.  I find Freeview looks quite blurry in comparison, crushes texture details, though granted the BBC tends to be the better of them all.

I don't watch broadcast TV very often though, so its kinda hard to compare, especially as despite their claims of aiming for a certain quality profile I find Netflix can vary a lot between content.
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sevenlayermuddle

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Re: 4K question?
« Reply #19 on: January 11, 2020, 07:13:28 PM »

I’m not a fan of contrast enhancement.   Imho the best person to judge the correct contrast ratio is the technical team who shot the movie.    I watched ‘Good Omens’ on Amazon’s 4K stream and had the distinct impression contrast and vibrancy had been deliberately over-enhanced, presumably to make 4K ‘look better’.  Some may like it but it didn’t work well for me, just made every single scene look like it had been shot in blazing sunshine, which soon became tiring on my eyes.

There’s really no mistaking the artefacts on the Netflix movie I watched last night.   One scene, very typical, where a camera pan was following an actor as he walked past a building with lots of architectural detail.  A kind of ‘halo’ forms around the actor, containing bits of brickwork that simply don’t belong at the screen location at which they are rendered.   :(
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Alex Atkin UK

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Re: 4K question?
« Reply #20 on: January 12, 2020, 05:20:50 AM »

I’m not a fan of contrast enhancement.   Imho the best person to judge the correct contrast ratio is the technical team who shot the movie.    I watched ‘Good Omens’ on Amazon’s 4K stream and had the distinct impression contrast and vibrancy had been deliberately over-enhanced, presumably to make 4K ‘look better’.  Some may like it but it didn’t work well for me, just made every single scene look like it had been shot in blazing sunshine, which soon became tiring on my eyes.

There’s really no mistaking the artefacts on the Netflix movie I watched last night.   One scene, very typical, where a camera pan was following an actor as he walked past a building with lots of architectural detail.  A kind of ‘halo’ forms around the actor, containing bits of brickwork that simply don’t belong at the screen location at which they are rendered.   :(

That sounds more like frame interpolation artefacts than compression, in which case a TV function not Netflix.  It may be enabled for Netflix and off for Freeview, as it can often be enabled/disabled per input/app.

I always keep it on as judder from panning at 24fps make me feel ill, so artefacts are a small price to pay and overall it allows you see more detail.
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sevenlayermuddle

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Re: 4K question?
« Reply #21 on: January 12, 2020, 08:52:08 AM »

I’ve always assumed it to be macro blocking. Next time I see the effect I’ll note the exact playback position then experiment later with different motion smoothing settings, it being currently set to lowest (not off).

Other half surprised me when we bought that TV as, after a few days, I enabled aggressive smoothing to see if I liked it.  She took one look and declared that it made movies looks like “soap operas”.  Which of course might be the term used by a person who had researched the topic with web searches.  Yet she had never done so, and she’s not otherwise sensitive to inadequacies of digital TV, “soap opera” was just the first term she thought of. :-\
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Alex Atkin UK

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Re: 4K question?
« Reply #22 on: January 12, 2020, 09:20:22 AM »

Yeah the thing with interpolation is it can be WORSE on a good quality source, because those sharp lines such as brickwork, car antennas, etc are so very high contrast and clean.  In some ways the lower quality the source, the easier it is to interpolate because that finer detail has already been compressed out of the image.  But when it works well, its high-quality material where you get the most benefit because interpolation lets you see the detail normally hidden by the harsh frame to frame transitions.

Macro-blocking is where you physically see squares in the video feed.

Its weird how people coined the soap opera effect and for some reason hate it.  Its actually more realistic, but just goes to show how freaky our brains are how we start to make associations that don't really make sense.  I find it especially amusing when PC gamers are all about higher and higher frame rates but can call me crazy for hating movies at 24fps because they are juddery and hard to focus on.
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sevenlayermuddle

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Re: 4K question?
« Reply #23 on: January 12, 2020, 11:20:19 PM »

I watched an Apple TV HD stream tonight, made sure smoothing settings were same as for TV’s native Netflix App and... same result... Apple still perfect, no noticeable artefacts at all.   Evidence is, at this stage, Netflix HD on my TV is being spoiled by Netflix-specific compression artefacts, probably macroblocking.

Quite apart from compression and bitrates, for a long time I found Netflix movies unwatchable because the black levels were very wrong, resulting in milky-looking dark scenes.   It was for all the world as if, at the encoding stage, they’d confused RGB and Studio levels.  I moaned about it on a kitz forum thread at the time. :(

The black level problem resolved itself a few months ago, all has been well on that front since then.    But pretty bad  that a company, who’s business is streaming, can be so incompetent as to get the black levels wrong, for months and months on end. :'(
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Alex Atkin UK

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Re: 4K question?
« Reply #24 on: January 13, 2020, 05:34:56 AM »

I certainly wont deny that on some movies at least, Netflix does a poor job.  My point was more that its not a problem across all content on Netflix, it seems to be a case by case basis.  Just as some movies for some bizarre reason they completely flatten the audio.

Ultimately their 4K material is usually pretty good, sometimes exceptionally so, but naturally can't come close to a good 4K Bluray with 3-6x the bitrate.
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sevenlayermuddle

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Re: 4K question?
« Reply #25 on: January 13, 2020, 09:40:43 AM »

@Alex, you got me thinking there.   I watch very little of Netflix's home-brewed material but there's exceptions, and I don't remember many problems watching their home brew.

Now, as mentioned earlier, my TV's built in App displays a bitrate on request.  It's a static figure, so not sure if it's an average or a ceiling or what, but I imagine it is meant to be meaningful as it seems to come from within the TVs Netflix App.  So, I've just tried starting an episode of 'The good place'.  After allowing time for it to adapt, bit rate shows as 5.53 Mbps.  On the movie I grumbled about earlier, 4.64Mbps is displayed.

Above is no conclusive proof of anything at all, just random observations, and the figures aren't all that far apart.  But it is consistent with my suspicions that Netflix don't try as hard as they might when streaming movies.  They may be concentrating their resources on making their own produce look good at the expense of real movies, which would probably make business sense, even if not what all customers want.
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Alex Atkin UK

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Re: 4K question?
« Reply #26 on: January 13, 2020, 11:24:57 AM »

It could also be that some of their less viewed movies they are more aggressive on vs popular stuff, or maybe even the opposite to reduce bandwidth costs?  There are so many reasons they could choose to encode different movies with a different bitrate budget.

They do claim to customise the encoding on a per-movie basis to use the least bitrate possible while maintaining a consistent quality, I wonder if sometimes it just gets it completely wrong?

I wonder even, if it could be that stuff your ISP has cached might have a different bitrate to stuff coming direct from Netflix?
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Chrysalis

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Re: 4K question?
« Reply #27 on: January 14, 2020, 07:58:32 AM »

For me netflix looks fine, I watch it in on my browser "most" of the time, netflix for some reason limit it to 720p in chrome, but if you emulate an apple browser, then it will play at 1080p, and for me thats absolutely good enough, miles ahead of things like now tv.

I am sure if I compared it to a bluray I would notice if I "looked for it", but end of the day for me 1080p is good enough to watch stuff.
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Alex Atkin UK

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Re: 4K question?
« Reply #28 on: January 14, 2020, 12:21:51 PM »

Yeah I'm in a different position where I no longer sit up to a computer table due to pain sitting in that kind of position.

So I sit in a reclining chair with my monitor to the left and TV directly in front.  So when you mostly only watch on a 55" OLED, the difference is much more obvious.

On my phone I can see the difference between 720p and 1080p, I can even tell 1440p is slightly clearer but its not something that screams at me like on the TV.  Its generally posterisation (sudden changes in colour gradients that aren't natural) that drives me insane, and that's something that lower bitrates inherently cause as its the contrast they throw away first to obtain the bitrate saving.

That's where Netflix vs Bluray can really be obvious, the picture will look deeper and more seamless due to the smoother colour transitions at a higher bitrate.  Though somehow with clever encoding and HDR they really do pull off impressive results.  I think its because Netflix LOVE night scenes in their shows, which can inherently compress down more efficiently.

There's also the fact that if you shoot using high-end digital, you get next to no grain so again it compresses down far more efficiently than film based material where the grain is an absolute pig to compress and removing it destroys detail in the image. (I'm looking at you Terminator 2 UHD Bluray)
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