[FFmpeg-devel] [PATCH] AAC Encoder: clipping avoidance

Rostislav Pehlivanov atomnuker at gmail.com
Sat Jul 18 00:09:35 CEST 2015

>attachment.bin:357: trailing whitespace.
>attachment.bin:436: trailing whitespace.
>attachment.bin:454: trailing whitespace.
You should probably configure your editor to strip that off automatically.

Why the change from (win+w)*2? Shouldn't you remove the entire loop around
w because now nothing depends on it?

There is a subtle difference at ~80k bitrate and the spectrals look a bit
better, specifically the low energy bands.
There is a lack of clipping however. There used to be some rare spikes
across the entire spectral range which are gone now.

On 17 July 2015 at 12:57, Claudio Freire <klaussfreire at gmail.com> wrote:

> Avoid clipping due to quantization noise to produce audible
> artifacts, by detecting near-clipping signals and both attenuating
> them a little and encoding escape-encoded bands (usually the
> loudest) rounding towards zero instead of nearest, which tends to
> decrease overall energy and thus clipping.
> Currently fate tests measure numerical error so this change makes
> tests using asynth (which are near clipping) report higher error
> not less, because of window attenuation. Yet, they sound better,
> not worse (albeit subtle, other samples aren't subtle at all).
> Only measuring psychoacoustically weighted error would make for
> a representative test, so that will be left for a future patch.
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