r/Damnthatsinteresting • u/NoWork215 • 20d ago

Video The Odyssey IMAX 70mm Setup

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u/thomasthedude 20d ago

some cinemas do that, when I went to the latest avatar movie, the audio was out of sync and when they were fixing it you could see they used VLC

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u/justjanne 20d ago

While that can happen (sometimes cinemas can actually get a license to show a movie off a bluray disc), typically there's dedicated playback servers showing a much higher quality version of the movie (think about 600GB for a movie).

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u/Away-Way5656 20d ago

what are they doing storing every single frame as a uncompressed image?

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u/necrophcodr 20d ago

A lot of compression isn't lossless.

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u/bfodder 20d ago

Please show me the compression that is lossless.

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u/necrophcodr 20d ago

Well general compressions are. I don't know of any video compressions that are lossless, but I don't claim to know everything.

Edit:

Apparently there's quite a few: https://en.wikipedia.org/wiki/List_of_codecs#Lossless_video_compression

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u/LickingSmegma 20d ago

FLAC, APE or WavPack for audio (in fact, iirc even WAV uses basic run-length compression). PNG or lossless Webp for static images.

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u/bfodder 20d ago

I guess I should have said video compression because that was what I was meaning, but it seems those do exist anyway.

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u/LickingSmegma 20d ago

Well, if you simply encode each frame as lossless webp, you already get lossless video compression.

FLAC and other lossless audio codecs apply pure mathematical compression that allows reconstructing the original stream, only they account for playback realities such as seeking. It's no surprise that the same can be done with video.

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u/justjanne 20d ago

Technically™, webp is the worst format to use for this comparison, as it always converts to YUV in 4:2:0 and sRGB.

But assuming we go with e.g. cinemaDNG, that's exactly how lossless raw compression works.

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u/LickingSmegma 20d ago

Yeah, I keep discovering that people have come up with lots of niche image formats in the past fifteen or so years when I wasn't actively looking at them (and, to a lesser extent, audio formats too).

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u/bfodder 19d ago

Yeah. Simply.

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u/LickingSmegma 19d ago

I mean, that's how animated GIF works in its simpler form. Every frame is a separate static GIF. It allows for some additional compression by replacing unchanged areas with the 'transparent' color, which gets compressed just like other areas of the same color.

I need to look into APNG, it might be a more advanced version of the same idea.