Ancestors

Written by fasterthanlime 🌌 on 2025-01-17 at 17:04

oh my god. OH my god.

https://obsproject.com/blog/obs-studio-hybrid-mp4

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Written by draeath on 2025-01-17 at 17:53

@fasterthanlime why can't the encoder initialize itself so that it can take its first sample as an actual input?

Such a strange decision, with such infuriating ramifications.

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Written by Josh Jersild on 2025-01-17 at 21:03

@draeath @fasterthanlime I've worked on codecs (not these ones): there are technical reasons for this to be the case - the filters that are used to decode an encoded audio stream, among other things, use overlapping techniques (probably something like an MDCT or ELT) which means the first outputs from said filters are necessarily going to contain unusable data.

Because of this, many (most?) codecs have some kind of priming scenario at stream start where zeros are fed into the filters to get them rolling, so that the first real audio data to go in will come out at the beginning of the first "meaningful" output sample. But since most of these filters are written as roughly "put N samples in, get N samples out" (it's not quite that because the input is in frequency domain, but close enough), the first batch or two have to be discarded by the code (somewhere) as they won't contain usable audio.

It sounds like this particular implementation just didn't do that part properly

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Toot

Written by Josh Jersild on 2025-01-17 at 21:04

@draeath @fasterthanlime (and, to be clear, this is an issue on the decode side, not the encode side)

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