Use Case: Frame rate conversion from 60 fps to 59 fps
A black-boxed encoder produces video with the fixed frame rate 60 fps. However a decoder at client’s side can not cope with the frame rate 60 fps, but it can keep real-time decoding of video streams with the frame rate 59 fps or lower.
Because the encoder supports frame rates 60 fps only, we sometimes should discard frames before delivering to the client to be sure that the client receives video with the frame rate 59 fps.
If we configure the encoder to generate video with GOP size equal to 60 frames; and each GOP is configured as closed one. Then we can discard the last frame from each GOP without compromising quality, since the last frame of GOP is not used for reference (bear in mind – GOPs are closed). We remove the last encoded frame in each GOP and consequently the frame rate is reduced to 59 fps (each second the decoder receives 59 frames, although encoded 60 frames):
One of advantages of closed GOPs is in ability to correct the frame rate by removal the last frame from each GOP.
23+ years’ programming and theoretical experience in the computer science fields such as video compression, media streaming and artificial intelligence (co-author of several papers and patents).
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