Remove support for FFmpeg 6.x and 7.0

[RytoEX]

Description

Remove code supporting FFmpeg 6.x and 7.x (FFmpeg < 8.0).

Specifically, remove compatibility code for FFmpeg 6.1 that targets:

• libavcodec < 62
• libavformat < 62

Motivation and Context

Removing FFmpeg<8.0 code. See:

• Dropping Support for Ubuntu 24.04, Qt 6.4, and FFmpeg 6.1 #13570

How Has This Been Tested?

It hasn't been tested yet.

Types of changes

• Code cleanup (non-breaking change which makes code smaller or more readable)

Checklist:

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

[PatTheMav]

Would this primarily require assistance to be tested on Linux?

[tytan652]

Some changes are breaking compat with FFmpeg 7.0.

[tytan652]

This removes support for FFmpeg 7.0 (61, 3, 100 for 7.0.3).

[tytan652]

This removes support for FFmpeg 7.0 (61, 3, 100 for 7.0.3).

[tytan652]

Specifically, remove compatibility code for FFmpeg 6.1 that targets:

* libavcodec < 62

* libavformat < 62

The bullet list does not align with the first statement, the version 61 of both is under FFmpeg 7.x.

Edit: 60 is to be excluded so "< 61" if only FFmpeg 6.x is removed

[RytoEX]

The "Remove code supporting FFmpeg 6.1" is a bit of a misnomer. The actual goal is "remove support for FFmpeg versions older than what Ubuntu 26.04 ships with", and that version is FFmpeg 8.0.

[tytan652]

Then it needs to be rename to something like "Remove support for FFmpeg 6.x and 7.0", the actual name is mismatching the scope of the change itself.

[RytoEX]

Then it needs to be rename to something like "Remove support for FFmpeg 6.x and 7.0", the actual name is mismatching the scope of the change itself.

Updated PR name. Will update commit messages later.

[RytoEX]

Updated commit messages. No code changes pushed.

[RytoEX]

Would this primarily require assistance to be tested on Linux?

That it compiles on Ubuntu is probably a sufficient compile test. Runtime testing on any OS should suffice.

[tytan652]

I think there is some find_package(FFmpeg in Cmake that do have a version as argument, they should be bumped.

[RytoEX]

I think there is some find_package(FFmpeg in Cmake that do have a version as argument, they should be bumped.

Added a separate commit changing the only find_package(FFmpeg that specified a version number. Semantically, the commits should probably be reversed.