decklink: Support different frame rate on decklink output

[norihiro]

Description

Dependency:

• Decklink: Use frame scheduling API to fix output audio drift #1865

Support different video frame rates on Decklink output.

• When the frame rate of decklink output is larger than that of OBS, frames will be duplicated to output enough frames.
• When the frame rate of decklink output is smaller than that of OBS, frames will be decimated.

This PR is based on the other PR #1865. The PR #1865 should be merged earlier than this PR. Please have a look at the last commit of this PR.

Motivation and Context

I want to set different frame rate on decklink output than OBS's frame rate.

On Intensity Pro 4K, it is required to set 525i59.94 for analog composite output but different sampling rate is required for streaming.

How Has This Been Tested?

• Set 720p50 on decklink output, set OBS's frame rate to 30 fps, confirmed there is no Late Frame log message.
• Set 1080p24 on decklink output, set OBS's frame rate to 30 fps, confirmed the number of buffered video frames does not increase.
• Set 1080p30 on decklink output, set OBS's frame rate to 30 fps, confirmed one frame is output for every OBS's frame.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[norihiro]

One design choice I have not decided yet is how to determine the number of frames to duplicate (nFrame in the code).
In this PR, I calculate based on the difference of frame rates for OBS and decklink-output.
Another idea I have, but not implemented in above commit, is monitoring GetBufferedVideoFrameCount and feedback to nFrame. This will not robust for the fluctuation of rendering time. However, it will compensate gradual increase of buffering on the devices without the ability of the timing adjustment (bmdDeckLinkConfigClockTimingAdjustment). Doing so, also need to implement something similar on WriteAudio.