Is BMPC4K 60Hz HDMI out synced to 120 Hz stored BRAW frames?

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Is BMPC4K 60Hz HDMI out synced to 120 Hz stored BRAW frames?

PostThu Aug 08, 2019 4:13 pm


This may be more of a camera hardware question, but this forum seems the most appropriate place to start.

My question: "is the BMPC4K BRAW storage frame rate at 120Hz synchronous with the HDMI output frame rate at 60Hz?" The resolution is of course 1920 X 1080.

I have a project that requires a Blackmagic Pocket Camera 4K to have specific 120Hz BRAW frames identified and frame synchronized to external hardware.

The external hardware uses the BMPC4K HDMI output to extract VSYNC at 60 Hz, and I need to confirm this will also create frame synced BRAW files at 120Hz. I'm not concerned about occasional dropped frames.

Here is my setup:

1. I set the camera to record BRAW 1920X1080 @120Hz and monitor the camera's HDMI output @60Hz while extracting the VSYNC from the camera HDMI output.

2. The external hardware generates a small audio tone burst every ten frames that is fed back to the camera's audio input in sync with the HDMI 60Hz frame rate. One tone burst is recorded to a single frame every ten frames.

3. The tone burst will show up on every tenth frame in the BRAW file if it is recorded at 60 Hz, but I'm not sure about 120Hz storage.

So I would like to set the internal record frame rate to 120Hz while monitoring and syncing to the 60Hz HDMI frame rate, and I wonder if this will result in a frame synced recording every 20 frames of BRAW storage.

Any thought or comments here would be greatly appreciated.

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