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>FFmpeg's AAC DEcoder is busted with regards to stereo PNS, and the bug may be in other AAC decoders too, so we work around it in the encoder. Since no other en
by HugoTea 3mo ago
>FFmpeg's AAC DEcoder is busted with regards to stereo PNS, and the bug may be in other AAC decoders too, so we work around it in the encoder. Since no other encoder used PNS, the bug was not found until now.
I don't know what PNS is, but I bet this has been bothering someone's niche use-case for 20 years
- mcoliver 3mo agohttps://www.audiolabs-erlangen.de/content/resources/aesCodingTutorial/pns.html https://www.audiolabs-erlangen.de/content/resources/aesCodin...
- dcrazy 3mo agoHah, this sounds like the audio equivalent of Netflix’s grain reconstruction.
- BoingBoomTschak 3mo agoNetflix's or AV1's FGS?
- dcrazy 3mo agoNetflix developed it as a member of AOM.
- lesscraft 3mo agoThe issue was twofold, on one hand, using TNS on top of PNS meant the noise that got inserted was shaped by TNS, which is nonsense since the decoder generated the noise, not the encoder. This made PNS explode. The second, biggest issue was that using PNS in combination with any stereo tools resulted in noise leaking in both channels equally, ruining stereo imaging. So the best and only thing to do was to enable PNS only if the band in both channels is noise (or is sufficiently non-tonal and masked).