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authorRostislav Pehlivanov <atomnuker@gmail.com>2015-09-06 15:13:18 +0100
committerRostislav Pehlivanov <atomnuker@gmail.com>2015-09-06 15:30:26 +0100
commit033e58941e684ac7190d6d1b06f31a677be4539f (patch)
tree2784b994d97fe8320e8dcc30d2f6bc7c7ecc7f87 /doc/ffmpeg-bitstream-filters.texi
parent8848c8440eb5816d5a9c3d38e0e20342867ef2cc (diff)
downloadffmpeg-033e58941e684ac7190d6d1b06f31a677be4539f.tar.gz
aaccoder: rewrite PNS implementation
This commit rewrites the PNS implementation and significantly improves sonic quality. The previous implementation marked an incredibly big amount of SFBs to predict when there was no need for this and this resulted in quite a large amount of artifacts. Also the quantization was incorrect (av_clip(4+log2f(...))) which led to 3x the intensity for PNS values leading to even more artifacts. This commit rewrites the PNS search function and introduces a major change: the PNS values are synthesized and are compared to the current coefficients in addition to passing through the revised checks to see whether PNS can be used. This decreases distortions and makes the current PNS implementation mainly focused on replacing any low-power non-zero bands as well as adding any zeroed bands back. The current encoder's performance is enough (especially with IS) so PNS isn't really required except to fill in the occasional few bands as well as extend any zeroed high frequency, so this combination which is already enabled by default works to get as much quality as it can within the bits allowed. Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
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