Baffled by render file sizes.

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chrisblandtv

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Baffled by render file sizes.

PostFri Nov 26, 2021 2:19 pm

I'm rendering 2 files, and am baffled by the difference in resultant MP4 file sizes.

Both input files are identical apart from duration. One file is twice the length of the other - it's actually the same content copied and pasted to make the timeline twice as long

They are both rendered using exactly the same delivery settings.
H.265, 3840x2160, 23.976fps, Quality restricted to 50000, VBR High Quality, Lookahead 16, AQ Strength 8.

File 1, 60 minutes in duration, produces a 4k MP4 file of 750Mb.

File 2, 120 minutes in duration comes out at 43Gb.

I'd really appreciate it if anyone could explain how a doubling of duration results in a file size 59x bigger? What am I doing wrong, please?
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stesin

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Re: Baffled by render file sizes.

PostFri Nov 26, 2021 10:30 pm

Pack 60 minutes of 4k UHD H.264 into 750 MB?
This is, hmmm, unbelievable.
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Charles Bennett

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Re: Baffled by render file sizes.

PostSat Nov 27, 2021 11:44 am

Are you sure the 120min version was done in h265?
I have a 20 minute h264 UHD 50fps render, restricted to 80Mbps, that comes out at 10.9GB.
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ZRGARDNE

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Re: Baffled by render file sizes.

PostSat Nov 27, 2021 1:01 pm

Resolve H.264/265 encoder isn't worth messing with.

Black Magic has provided zero documentation for their constant quality encoder. The H.265 VBR 'Best' is garbage.


Export as DNxHR HQ and use a tool that actually had some intelligence going into its design, Handbrake.
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Noerde

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Re: Baffled by render file sizes.

PostSat Nov 27, 2021 1:51 pm

ZRGARDNE wrote:Resolve H.264/265 encoder isn't worth messing with.

Black Magic has provided zero documentation for their constant quality encoder. The H.265 VBR 'Best' is garbage.

Export as DNxHR HQ and use a tool that actually had some intelligence going into its design, Handbrake.


Isn't handbrake more or less a gui for ffmpeg though? So it's basically adding some good defaults/presets to ffmpeg and some optimizations to its encoder?

And you can use ffmpeg within Resolve too as a plugin. I mean I fail to see how the design can be compared with 2 different kind of programs. Quality of the encoding software or exposed and changeable/chosen parameters maybe.
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stesin

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Re: Baffled by render file sizes.

PostSat Nov 27, 2021 7:07 pm

ZRGARDNE wrote:Resolve H.264/265 encoder isn't worth messing with.

Black Magic has provided zero documentation for their constant quality encoder. The H.265 VBR 'Best' is garbage.


Export as DNxHR HQ and use a tool that actually had some intelligence going into its design, Handbrake.
For H.264/265 DVR's "best" just doesn't mean "best IQ" but "best" for some different purpose which I'm not aware of.

Use H.264/265 VBR with manual bandwidth "cap" setting. Works exactly as expected.
Blackmagick DaVinci Resolve Studio 17.4.6
Blackmagick Speed Editor USB cable connected
Linux Ubuntu 22.04 (5.18.14)
Asus G750 i7-4860HQ 32GB RAM
NVidia 980M 8Gb (510.85.02 CUDA: 11.6)
2x166GB SSDs in RAID0 - DVRS Caches
1x4TB Samsung EVO 870 SSD

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