Added support for FFMPEG 8.0

[devilish-crow]

Removed the newly deprecated libavformat flags, detailed in the following commits:

• https://ffmpeg.org/pipermail/ffmpeg-devel/2023-September/314836.html
• https://ffmpeg.org/pipermail/ffmpeg-devel/2023-August/313668.html
• https://patchwork.ffmpeg.org/project/ffmpeg/patch/20230413162940.61095-3-jamrial@gmail.com/
  Replaced the deprecated key_frame field with the proper flag, which since the latest ffmpeg development version is the only way to check for key frames.
  Updated snapshots as the duration values changed.

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[devilish-crow]

I've already signed with cla assistant but for some unknown reason it refuses to update my status.