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When using lossy encoding can similar adjacent video frames become merged or even identical?

For example, if frames A, B and C occur in sequence and are similar but different, can the encoded video render A, A, A when played?

I am referring to this tweet from Channel 4 News that implies that the veracity of a video can be called into question if, in its encoded form, frames are replaced with adjacent frames.

It would seem to me that the observed playback could be symptom of inter-frame compression - possibly performed multiple times due to repeated encoding and decoding. Could this be what happened?

Another idea: could differing US/UK framerates also affect the rendered output due to frames falling in between the eventual rendered (possibly different) framerate?

Marcus Müller
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52d6c6af
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    "lossy encoding" can be anything; in fact, even "convert every frame to complete blackness" is a lossy encoder. So yes. And yes, even for realistic, feasible compression, that's not so unlikely, even in practical means. If two frames are almost the same in uncompressed form, and the change is miniscule enough for the compressor to compress it away, then logically it follows that the frames become identical. – Marcus Müller Nov 09 '18 at 12:12
  • The interesting question here is: Why do you think there's a restriction about this? What motivates asking this question? I think there's a "larger" question behind this, and it would make for a very interesting question to add that as context by editing your question. – Marcus Müller Nov 09 '18 at 12:18
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    I have updated the question, – 52d6c6af Nov 09 '18 at 12:21
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    Ah, that puts it in a much more practical context, because it also defines which codecs might have been involved, and what kind of video (cartoon/stop motion animation / real life video). – Marcus Müller Nov 09 '18 at 12:24

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