YouTube streaming - bitrate limit

[Deleted member 330497]

Hello everyone!
I have been wondering: what is the current bitrate limit for YouTube live streaming for 1080p@60fps?
I would like to stream action games on YT with 1080p@60fps with NVENC codec. Which stream key should I use? The variable one or the 1080p (3-6Mbps)? On the other hand, the YT support page suggests the range of 4-9Mbps (https://support.google.com/youtube/answer/2853702). I think that streaming 1080@60 with 6 or 9Mbps bitrate is not enough for dynamic games. My upload speed is 30Mbps so I can safely stream with 15Mbps bitrate. However, will it make any difference for quality of the stream or YT just cuts the quality for 1080p streams at about 6-9Mbps? I have already been doing some streaming tests comparing 6Mbps and 12Mbps bitrate but I am unable to say for sure there is a difference between them.

 

[Tomasz Góral]

Everything you send is reencoded to the standard values adopted by YT.
For 1080p60 resolution the typical stream is about 4.5Mb / s, so if you send 4.5Mb / s your data must be recoded anyway, and because the compression is lossy, each subsequent encoding may introduce losses in image quality.
I send 9 Mbps for 1080p50.
But by increasing the scaled resolution from 1080p to 4K, I send a stream of 20-25 Mb / s.

 

[TryHD]

garbage in garbage out, stream the highest quality you can achieve with your limitations to youtube so they can make the best out of it. Best would be to deliver 1440p or higher to them because youtube encodes that resolutions with more bitrate than 1080p or lower.

 

[Deleted member 330497]

Are you guys aware if the max suggested bitrate for 1080@60 (which is 9 Mbps) includes audio bitrate? I mean is it 9 Mbps bitrate just for video or it also includes audio bitrate (my audio bitrate is 128 Kbps) leaving 8872 Kbps for video (9000 - 128 = 8872 Kbps)?
Does streaming with higher bitrate than the top recommended one (9 Mbps) actually provide any quality difference for 1080p at 60fps? Unfortunately I am unable to stream at 1440p because my display is 1080p and OBS does not allow me to upscale the output resolution to 1440p.

 

[TryHD]

Are you guys aware if the max suggested bitrate for 1080@60 (which is 9 Mbps) includes audio bitrate? I mean is it 9 Mbps bitrate just for video or it also includes audio bitrate (my audio bitrate is 128 Kbps) leaving 8872 Kbps for video (9000 - 128 = 8872 Kbps)?

doesn't matter ignore bitrate recommendations on youtube

Does streaming with higher bitrate than the top recommended one (9 Mbps) actually provide any quality difference for 1080p at 60fps?

Yes, like i wrote garbage in garbage out, if you have artefacts because the bitrate was insufficient for your content it will also be in the youtube reencode.

Unfortunately I am unable to stream at 1440p because my display is 1080p and OBS does not allow me to upscale the output resolution to 1440p.

You can stream whatever resolution you want, you can simply type your desired resolution in the Output (Scaled) Resolution field instead of using dropdown.

 

[Deleted member 330497]

@TryHD
Thanks for explanation! Are you aware if there's any real advantage (in terms of quality) by streaming 1080p@60 with the OBS output (scaled) resolution set at 1440p (2560x1440)?
I have found some information which state that streaming in 1440p makes YT use the newer, better codec - VP9. I have already tested it out and turns out it's true! If I stream with the output resolution set at 1080p YT uses AVC1. Once I changed the output resolution to 1440p YT used VP9. Is the difference in quality between these two significant? To put it simple: is my effort by changing the output resolution worth it? If so, what bitrate would you recommend for streaming 1440p@60fps for fast-paced action games?

YT suggestion:

1440p @60 fps

• Resolution: 2560x1440
• Video Bitrate Range: 9,000-18,000 Kbps

 

[TryHD]

It depends on the content you stream, for fast paced games like quake 3 it is worth, if you play chess or so not. Bitrate wise go as high as your connection can handle. The bitrates you quote are the recommended minimum so ignore them.

 

[konsolenritter]

I mean is it 9 Mbps bitrate just for video or it also includes audio bitrate (my audio bitrate is 128 Kbps) leaving 8872 Kbps for video (9000 - 128 = 8872 Kbps)?

Okay, so w're talking about 1,4% of the available bandwidth. Do you mean that 1,4% more or less makes a big deal to the video encoding, really? ;)

Why do you want to stream in 1440p (even upscaled, what makes it even worse...)? (Upscaled material is blurried by nature, what makes it harder to the encoder from frame to frame...) So for a slightly better downstream from yt to your viewers you make it even harder for your encoder and upstream. Uuummh.

Streaming at 1080p means more bits per resolution available (to your encoder) than streaming 1440p by the same bandwidth.

 

[Tomasz Góral]

Upscaled material is reencoded diffrent codec (betters) like video sender as 1080p.
And now comparing 1080p vs. 1440p or 2160p, better quality got on higher resolution if you compared the same resolution.

 

[konsolenritter]

@Tomasz Góral
So upscaled 1080p material on 2160p should outcome of yt better than native 1080p, got it right?

I know that yt will need more bandwidth to just even compensate for the needs of higher resolution (2160 is four times the area of 1080). But i can't imagine that 1080p upscaled in 2160p should look even better then... :o Sounds very astonishing to me.

 

[Tomasz Góral]

better is codec who compressed picture.

 

[Deleted member 330497]

Okay, so w're talking about 1,4% of the available bandwidth. Do you mean that 1,4% more or less makes a big deal to the video encoding, really? ;)

My point was: if theoretically YouTube has the max limit cap set at 9 Mbps (for 1080p) then sending any additional BIT would not be received/accepted by them causing loss of video or audio quality (because if you stream with video bitrate at 9 Mbps + 128 Kbps audio bitrate you exceed the limit). Alternatively, sending at bitrate higher than 9 Mbps would make no difference as their encoder would downscale everything to the cap of 9 Mbps. I am not aware if such a hard limit on YT-end exists or how their encoder works in practice, that's why I'm asking you guys to get some knowledge on how it all works :-).
It would be pointless to stream with let's 50 Mbps bitrate and find out you will get the same video quality as streaming with 10 Mbps bitrate.

Why do you want to stream in 1440p

To get the support of VP9 codec. Streaming in 1080p makes YT use AVC1 codec. I have already done some tests and there's a difference in video quality but I'm unable to determine if the rise in quality of the video is significant enough for all the downsides of upscaling (more load on the cpu or rather GPU in my case - NVENC, requirement of higher bitrate so higher bandwidth load, a risk of artifacts - I hope there're none to expect).

 

[konsolenritter]

My point was: if theoretically YouTube has the max limit cap set at 9 Mbps (for 1080p) then sending any additional BIT would not be received/accepted by them causing loss of video or audio quality (because if you stream with video bitrate at 9 Mbps + 128 Kbps audio bitrate you exceed the limit). Alternatively, sending at bitrate higher than 9 Mbps would make no difference as their encoder would downscale everything to the cap of 9 Mbps. I am not aware if such a hard limit on YT-end exists or how their encoder works in practice, that's why I'm asking you guys to get some knowledge on how it all works :-).

Aah. I see your point. But i can assure you that YT isn't dropping bits "the easy way". That is technical impossible. Simple dropping or truncation of data is only possible in the special event of totally-ordered bits, i.e. when all the bits are in a strong order from highest to lowest meaning or vice versa. That is not the case with multimedia codecs. What you send over, they must feed into their codec. Multiplexed video and audio streams are very complicated. So every bit, byte and kilobyte sent to youtube have to be processed by their servers. They can't just cap or cut (in terms of truncation) bits here and there. You have to know that Youtube completeley re-encodes your whole material. Going this way they are free to use an independent bitrate from yours (total decoupling their distribution network bandwidth from yours during the upload to them). The aim of Youtube is (understandably) to save bandwidth within their infrastructure (CDN) behind their ingestion (front) servers. If there is a hard limit, the solely possibility for YT would be to deny and break your upstream completely and enforce you to use a lower bitrate. You would know...

It would be pointless to stream with let's 50 Mbps bitrate and find out you will get the same video quality as streaming with 10 Mbps bitrate.

Anyway you are right on that. Due to the total decoupling by re-encoding the material YT is free to set their final demand on quality maximum. You are encouraged to send best possible material anyway, because every process of re-encoding brings a slight degradation in video (or audio) quality, ever!

The strict inequality (unfortunately) says:
- If you send already degraded material, youtubes re-encoding doesn't make it any better (gain of quality impossible due to physics),
- If they demand low bitrate as output of their re-encoders, your material will degrade anyway (you can't avoid that),

Conclusion: You should send over material as good as possible, but you can't prevent YT from any degradation, if they will (save bandwidth on their side).

Regarding their VP9 stuff i'm not sure. You are surely right on that. But as i wrote: To encode the squared (due to increased resolution in x and y) a huge amount of the additional bandwidth is needed to compensate against lower resolution. If there is more bandwidth available to get even better encoding of the material itself, ...i don't know...
Yes, it would be definitely interesting to test this. But rethink: Not all visitors and viewers of YT streams are capable to handle 2k or 4k on their own side. Resulting in the YT viewer to downsize and shrink the material to the viewers window. Even more a thing that YT does have under their control, not yours. :)

 

[TryHD]

But rethink: Not all visitors and viewers of YT streams are capable to handle 2k or 4k on their own side. Resulting in the YT viewer to downsize and shrink the material to the viewers window. Even more a thing that YT does have under their control, not yours. :)

What do you try to say with that?

 

[Deleted member 330497]

One of the arguments against streaming above the YT-recommended bitrate I have read numerous times over the internet is that streaming at higher bitrate (much higher than the recommended) causes an issue with video buffering for low-end users/devices (like phones, tablets or budget laptops). Any idea if it's true?

 

[konsolenritter]

What do you try to say with that?

Its about the youtube web player (the clients side). As streaming people we don't have control or influence of the viewers side. You can send 2K or 4K, but if the viewport on clients side is smaller, then YT controls how to downscale into that. I don't know if its bilinear, lancosz or something else. It's up to decisions made by YT. And if client-side settings to default, YT chooses the next "fitting" bandwidth/resolution for us.

 

[konsolenritter]

One of the arguments against streaming above the YT-recommended bitrate I have read numerous times over the internet is that streaming at higher bitrate (much higher than the recommended) causes an issue with video buffering for low-end users/devices (like phones, tablets or budget laptops). Any idea if it's true?

YT re-encodes the upstream simultaneously to different (smaller) bandwidth settings. So if you upstream in 1080p, YT provides 720p, 480p aso. additionally. By default the player on client side measures and guesses the available bandwidth. If they detect a bottleneck, the video will be switched to a lower bandwidth stream after short lag. To be fair: YT is good at these things. So are their developers of the webplayer technology, to be honest.

 

[Deleted member 330497]

YT re-encodes the upstream simultaneously to different (smaller) bandwidth settings. So if you upstream in 1080p, YT provides 720p, 480p aso. additionally. By default the player on client side measures and guesses the available bandwidth. If they detect a bottleneck, the video will be switched to a lower bandwidth stream after short lag. To be fair: YT is good at these things. So are their developers of the webplayer technology, to be honest.

So it turns out that the theory about video buffering issue is more of a myth than an actual thing?

Also, one more thing I would like to ask you guys about is Downscale Filter. In my case i do upscaling (1080p to 1440p), so does the Downscale Filter take part in it? If so, which one would you suggest for game streaming? I have read that Bicubic is (for some reason) more suitable for games while Lanczos is useful for streaming people, real world and such.

 

[TryHD]

YT re-encodes the upstream simultaneously to different (smaller) bandwidth settings. So if you upstream in 1080p, YT provides 720p, 480p aso. additionally. By default the player on client side measures and guesses the available bandwidth. If they detect a bottleneck, the video will be switched to a lower bandwidth stream after short lag. To be fair: YT is good at these things. So are their developers of the webplayer technology, to be honest.

How does that matter at all for the streamer? Like why bring it even up? It is not in your controll. Also you won't stream in a lower resolution because of it.

So it turns out that the theory about video buffering issue is more of a myth than an actual thing?

Also, one more thing I would like to ask you guys about is Downscale Filter. In my case i do upscaling (1080p to 1440p), so does the Downscale Filter take part in it? If so, which one would you suggest for game streaming? I have read that Bicubic is (for some reason) more suitable for games while Lanczos is useful for streaming people, real world and such.

I prefer bicubic, lanczos has to many ringing for me.

 

[Deleted member 330497]

What do you guys think about Psycho Visual Tuning? Is it worth enabling? NVENC OBS Guide recommends to enable it but I have found some posts here on the forum that suggest to disable it. What is your experience with that feature?