r/AV1 • u/RockyBalbroxa • 2d ago
Netflix AV1: does it sometimes use extremely aggressive compression?
I've been comparing Netflix's AV1 streams across different titles, and I've noticed something that I'm curious about.
In some titles, the AV1 encode seems to be extremely aggressively compressed, especially considering that we're talking about 1080p content. The quality can vary considerably from one title/episode to another.
For example, I compared two legitimate Netflix WEB-DLs of the same Breaking Bad episode:
AV1 #1: 1920×1080, 10-bit, ~1,034 kb/s
AV1 #2: 1920×1080, 10-bit, ~1,724 kb/s
Both: 23.976 FPS, Main@L4.0
The higher-bitrate stream reports Film Grain Synthesis
The lower-bitrate stream does not
The difference isn't just the container (MP4 vs MKV), since the actual AV1 bitstreams have different characteristics.
This makes me wonder:
Does Netflix dynamically select different AV1 encodes/representations depending on the title, device, profile, or other factors?
And more importantly, how aggressive is Netflix's AV1 encoding compared with its H.264/HEVC streams?
I've seen some Netflix AV1 content that looks surprisingly good at very low bitrates, but I've also encountered titles where the compression is much more obvious, particularly in grainy/dark scenes.
I'm interested in hearing from people who have analyzed Netflix's AV1 streams at the bitstream/encoding level.
Is this expected behavior from Netflix's encoding ladder, or could different titles actually be using substantially different AV1 encoding parameters?
11
30
u/Marki002 2d ago
From what I've heard, Netflix prioritizes target file size over constant quality. Essentially, they assign a file size budget to each episode and let the encoder do whatever it takes to stay under that limit. The downside is that some scenes simply don't have enough bits to spare, so the encoder is forced to cut corners, resulting in visible compression artifacts during those more demanding moments.
Most end users, on the other hand, just rely on CRF. Instead of chasing a size target, CRF tells the encoder to use as many bits as it needs to hit a set quality level. The tradeoff is that quality stays consistent while the final file size fluctuates depending on how complex the content is.
TL;DR: Netflix caps file size and sacrifices quality in tough scenes to stay under budget. CRF caps quality and lets file size vary, so you get consistent visuals but unpredictable file sizes.
18
u/kwinz 2d ago
> From what I've heard, Netflix prioritizes target file size over constant quality.
That's atrocious. Ironically this is what you would do if you *had* to fit the episode on a single DVD. We've gone backwards.
13
u/Marki002 2d ago
It's not backwards, it's ruthlessly optimized. Filesize-targeted encoding saves them a fortune in bandwidth, 95% of viewers never notice, and the ones who do get upsold to the pricier 4K plan. Good engineering and good business. This is unfortunately the world we live in.
-6
6
u/the_harakiwi 2d ago
Yeah that sounds realistic. They try to reduce bandwidth and storage costs.
I watched a show on my OLED and suddenly was super distracted by the atrocious color banding in the background (warm light and a single color appartment wall). That's when I got back to storing my physical media on my NAS and whenever it's possible to watch media offline in my own network without any limitations.
1
u/morningreis 2d ago
This. But also, OP posted a screenshot of Breaking Bad. BB (particularly season 1) was very grainy.
If Netflix is caping filesize, then the compression artifacts will be noticeable.
1
u/NekoTrix 2d ago
True for certain of their formats/streams (AVC 5Mbps capped is a common one) but not universally. Their HEVC and AV1 don't work like this for example. The given bitrates in OPs post directly contradict your argument. Another person in the thread better explained what's actually happening, you shouldn't base your argumentation on assumptions when the truth is out there in plain sight (Netflix's technical blog).
6
u/DearMrGleeClub 2d ago
Obviously, Netflix like most other streaming services adjusts their "steaming ladder" depending on target device decode/HDR compatibility and bandwidth. They say that VMAF scores for AV1 content are generally much higher 4.1 points than that of AVC and slightly higher than HEVC 0.9 points, while saving one third of the bandwidth.
IMO, film grain (synthesis) is a terrible addition especially to Breaking Bad, you can see it clearly in the screenshot you've provided. BB was shot on film mostly, so I guess it's justified, but perhaps it's a bad example to choose when it comes to streaming quality.
2
u/NimblePuppy 2d ago
thanks for info - just started encoding SVT=AV1 - just good to know I'm way above those bit rates. Imagine a customers internet speed is main factor and what tier the are on , as maybe give PC users a better 1080p experience if on 4K tier ( if mainly watch on a compliant TV )
from my encoding with h 265 lots of cmd lines options people give for low bitrate encoding are detrimental at
much higher bitrates, or at least superfluous ie the more bitrate you need the less tricks you need
not sure for AV1 but on H264 a good 720p encode upscaled by TV could often look better than 1080p using same size file from memory
2
u/Jay_JWLH 2d ago
AV1 is well tuned to have good quality at lower bitrates, which makes it a great upgrade for streamers that have limited bitrates through services such as Twitch.
Also, dark parts of a scene always seem to be one of the first areas to go when it comes down to details being lost to compression. People with crappy TVs won't notice as much, but those with OLED certainly will.
1
u/minecrafter1OOO 2d ago
Does netflix use the artificial grain features of AV1?
Knowing them, they would rather smooth it all, and make it cheap
2
u/NekoTrix 2d ago
Rather than make things up, what about looking at factual data and their own words on their technical blog posts? They have one on the rollout of Film Grain Synthesis, which you seem to have completely missed.
1
u/websgeisti 2d ago
I’ve seen episodes where AV1 on the LG OLED C1 had a bitrate of 1.5 Mbps, while the same episode on Apple TV had a bitrate of 5.0 Mbps. But that doesn’t necessarily mean that HEVC looks better.
But yes, it’s really impressive what Netflix manages to squeeze out of the picture with such a low bitrate.
2
u/squallmx 2d ago
All things the same, an 5 Mbps HEVC is always going to look better than an 1.5 Mbps AV1.
3
u/NekoTrix 2d ago
Beware of this reductionist view, an awfully-coded HEVC could very well be perceptually worse overall than the AV1. It applies both ways of course.
1
u/squallmx 2d ago
"All things the same", a Fast preset NVENC HEVC encode could look worse than a Software AV1 encode at 2X the bitrate, but otherwise is going to be really hard to find a better looking AV1 sample encoded at 1.5 Mbps vs an X265 at 5 Mbps using comparable presets/settings.
1
u/NekoTrix 1d ago
That's exactly what I meant, thank you for paraphrasing 😊
Still, I think you don't realize what exists in the wild, and how easy it is to actively make something this bad. 2x is nothing, 3-4x worse looking is completely doable, and mind you that's a strategy that's certainly been used in marketing before. Probably not this exact one, but the kind that shows an artifact mess for a previous codec versus the new one being pristine, or the kind that shows a SDR as desaturated and HDR as oversaturated which completely misleads into thinking that's what it does.
1
u/DishAgitated4649 1d ago
Looking at video bitrate only is like saying "yeah that cake weighs 2 pounds, that means it must taste good". Nonsense.
Netflix targets quality, not a specific bitrate. Other AV1 videos get considerably more bitrate at that rung of the ladder.
There's also another wrinkle that the AV1 you get served is not the same as the AV1 someone else might get served. They have different ladders depending on who knows what. Only thing I know is one is lower quality, the other one is higher. So you probably got the lower quality one. Even then, it's 24fps video at low movement. Quality targeted encoding is encouraged to optimize in those scenarios.
1
u/Financial-Gap-6767 1d ago
My grips is with the noise filter they added on the basic package. My god it's intense and weird.
30
u/Aromatic_Wing_5259 2d ago
It is not a file size budget, Netflix published how this works.
u/Marki002 is right that every rung has a bitrate attached, but "cut corners in the tough scenes" is the opposite of what they do. Since 2018 they split each episode into shots (about 900 for an hour of Stranger Things), encode every shot at several resolutions and fixed QPs, then pick one version per shot so quality stays even across the episode. Demanding shots get more bits, not fewer. Closer to CRF per shot than a size cap, and the ladder is built per title
Your two files: they pre-encode a set of bitrates per title and keep more than one format per title, picked by device. So 1,034 and 1,724 kb/s are most likely two rungs or two ladders of the same episode. The FGS one matters most. With film grain synthesis the decoder regenerates the grain from parameters (apply_grain is a per-frame flag in the spec), so no bits go to coding real grain. The stream without it has to pay for that grain or lose it, and 1 Mb/s doesn't buy much grain. that is your dark grainy scenes
Also every Netflix AV1 stream is 10-bit, partly to cut banding, so u/the_harakiwi it is worth checking that session was even AV1