Bad render quality on M1 Mac compared to PC

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RealityStudioLLC

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Bad render quality on M1 Mac compared to PC

PostMon Dec 06, 2021 6:59 pm

Hi all, I just got a Mac Mini M1 to toy with since everyone seems to be raving about them but I'm having an issue. I have Davinci Resolve Studio 17 installed on both that Mac and my usual PC Laptop with has an NVidia 3050ti.

Long story short I have one of my typical projects which is 100mbps h264 4k 30fps source from a Sony A7S3 and I render it out on both machines to my usual setting of 10000kbps h265 4k 30fps MP4. Problem is that the video rendered on my PC laptop looks great as usual, but the video rendered on the Mac M1 looks unusably terrible.

Both files are same output specs of MP4 h265 10000kbps 4k 30fps and both files are around the same size with the Mac file around 570MB and PC file around 580MB. Given how much people rave about the M1 Macs for video use means I must be doing something wrong, but I don't know much about Macs truth be told so I'm not sure what's going on. I attached pics of render settings on both PC and Mac versions. I figure it's just something stupid that I'm doing, but no clue what that is :( Any help appreciated!

Resolve MAC.png
Mac settings
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Resolve PC.png
PC Settings
Resolve PC.png (34.84 KiB) Viewed 313 times
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ZRGARDNE

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Re: Bad render quality on M1 Mac compared to PC

PostTue Dec 07, 2021 12:40 am

10 mb is very low bit rate for 4k footage.

Resolve does not have a CPU encoder for h.265. It is at the mercy of the GPU encoder. Nvenc typically gets a lot of flack for not looking so great. So I am surprised the M1 is worse. though I have never seen anyone do direct comparisons, you will find plenty for Nvidia vs AMD.


Regardless, Black Magic has done a quite poor implementation of H.264/265. The VBR presets of good/best are junk. If you actually want best quality at reasonable file size you need constant quality, which Resolve has, but has zero documentation on how to set the 4 quality sliders.

So I and many others choose to use a properly built encoder, Handbrake. Export from Resolve in Prores HQ and use Handbrake to compress to H.265. You will find many guides on optimal settings for it. Under the hood it is just FFMPEG if you are happy to go CLI route instead.
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RealityStudioLLC

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Re: Bad render quality on M1 Mac compared to PC

PostTue Dec 07, 2021 2:04 am

I've used Handbrake for more years than I can recall but personally I find NVEnc on the 30xx series of cards to be just as good so I switched to it some time ago. It will depend on your application naturally, I have to balance server storage costs, server backup costs, archiving costs, bandwidth costs, the user download experience, etc along with quality. For my productions and the particular type of content I film a 30xx series NVEnc encoder at 10000kbps actually works really well but your mileage may vary.

I'll have to try constant bitrate and see how that goes. This is all a bit of an experiment for me as I'm a Vegas Pro user but currently toying with Resolve Studio since it's multi platform but man I was just really surprised how poor the M1 encoder was.
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RCModelReviews

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Re: Bad render quality on M1 Mac compared to PC

PostTue Dec 07, 2021 3:34 am

ZRGARDNE wrote:10 mb is very low bit rate for 4k footage.

I totally agree with this statement.

I would never use a bitrate that low for 4K footage.

Even my action cams deliver their footage at 40Mbps and they're laden with compression artifacts so 10Mbps would look horrible.

I suspect that perhaps your PC's encoder isn't honoring the 10Mbps setting you've selected and is probably rendering at a much higher rate. Check out the actual bitrate of the resulting files to confirm that.
Resolve 15.3 Studio, Fusion 9 Studio
CPU: i7 8700, OS: Windows 10 (1709) 32GB RAM, GPU: GTX1060/6
I'm refugee from Sony Vegas slicing video for my YouTube channels.
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RealityStudioLLC

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Re: Bad render quality on M1 Mac compared to PC

PostTue Dec 07, 2021 4:24 am

I did check and renders from Resolve Studio and Vegas Pro both honor the 10000kbps setting. For example in this particular test case I used a 7:37 minute video and ended up with a 596MB file from Resolve Studio (NVEnc 30xx) and almost identical size from Vegas Pro (NVEnc 30xx). Running the math:

File size == 596MB
7:37 video == 457 seconds
596/457 = ~1.3MB/s
1.3MB/s == ~10.4mbps
10.4mbps == ~10400 kbps

...so every so slightly higher but within range considering it's VBR rendering. I attached a pic of the data as reported by explorer as well, that calculation should be more accurate as it's not rounding as I am.

I don't want to veer off into the woods here but encode quality at a given bitrate, aside from encoder quality of course, really depends on the content you film, how it's filmed and where it's filmed. For example my content is purely indoors so no random sunlight to alter large amounts of the lighting every frame, lighting is very controlled which helps the encoder quite a bit. I don't move the camera much when filming so limited delta per frame. I film fairly shallow at f1.8 so much of the scene is soft with maybe <30% needing detail from the encoder. Plus none of this is real time so the encoder can look ahead to determine exactly what bitrate it needs compared to a video camera codec that films real time which must brute force with bitrate to avoid artifacts.

Anyways for my needs it works very well and has passed blind tests against Handbrake. To be clear I'm talking about NVEnc in NVidia 30xx gpus. The previous generation of NVenc in the 10xx gpu's was not as good and neither is even the latest Intel Quicksync, I stuck with Handbrake after trying those. It specifically took the 30xx series of NVEnc to get me to switch. Plus my stuff isn't projected to 100 foot screen sizes, it's mostly views on laptops and tv's.
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Uli Plank

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Re: Bad render quality on M1 Mac compared to PC

PostTue Dec 07, 2021 5:19 am

To know all about your clips, there's MediaInfo (free).
Don't approach Resolve with your expectations from other NLEs! They are all different.
Resolve Studio 17.4.3 , macOS 12.1
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