Reverse Telecine with Passthrough of Settings

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Level 1

9 points

Reverse Telecine with Passthrough of Settings

I have footage shot with a Sony a7SIII in XAVC S. I am trying to transcode the footage from 29.97 fps to 23.976 fps (reverse telecine) while retaining all other settings (passthrough) including 4:2:2 chroma subsampling and 10 bits bit depth.

Original Media Specs:

Bit rate: 140 Mb/s

Format profile: High 4:2:2@L5.1

Color space: YUV

Frame rate: 29.970

Scan type: Progressive

Bit depth: 10 bits

When I use Compressor to transcode to Quicktime H.264, below are the specs:

Bit rate: 42.8 Mb/s

Format profile: Main@L5.1

Color space: YUV

Chroma subsampling 4:2:0

Bit depth: 8 bits

Frame rate: 23.976

Scan type: Progressive

Note the much lower bit rate, chroma subsampling change from 4:2:2 to 4:2:0, and bit depth from 10 bits to 8 bits.

I transcoded to ProRes 422 also, specs below:

Bit rate: 448 Mb/s

Format profile: 422

Color space: YUV

Chroma subsampling 4:2:2

Frame rate: 23.976

Scan type: Progressive

Retaining 4:2:2 Chroma subsampling. Bit depth oddly is not listed. Is that not a thing with ProRes. But bit rate is 3x larger and the files are too large for my tastes.

Would appreciate any suggestions or tutorials how to enable passthrough while simply changing the framerate. Thank you!

Posted on Oct 24, 2023 11:01 AM

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Answer 1

BenB

Level 6

12,535 points

Nov 8, 2023 1:36 PM in response to logam11

ProRes is not as compressed as H.264 and is handled with more detail to image quality. Yes, ProRes has always been a larger file than the very highly compressed H.264. Transcoding has always been a balancing act between image quality and file size. And yeah, ProRes determines the necessary bit rates on its own.

I'd get off the word "passthrough" and just focus on settings that get me as close to what I have to deliver to the client as possible.

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Answer 2

logam11 Author

Level 1

9 points

Nov 10, 2023 8:27 AM in response to BenB

BenB, appreciate the info. I actually have a decent grasp of ProRes and it's advantages over compressed H.264. Certainly if one possesses rack servers filled with hard drives in a professional environment, ProRes is the easy fix. Original XAVC file size was 3.4 GB, H.264 file was 1.3 GB, while the ProRes version was 10.7 GB. So ProRes files are more than 3x larger than the original.

As previously mentioned, main goal was to find a file format that would retain the original XAVC 4:2:2 chroma subsampling and 10 bits bit depth. The solution ended up being HEVC (H.265). I was able to choose the output chroma subsampling and bit depth that I wanted, along with reasonably sized files.

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Reverse Telecine with Passthrough of Settings

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