This commit once again improves the PNS implementation by scaling the
thresholds with frequency. The thresholds get looser as the frequency
increases since higher frequencies are basically noise to human ears.
Also, this introduces quantization error correction for PNS. Should
the error be too much, no PNS will be used. The energy_ratio is used
to regulate the actual encoded PNS energy: if the generated PNS
energy is higher than the energy from the psy system, energy_ratio
is used to correct it so that hopefully once requantized and
transmitted the value in the decoder will be closer to what the
encoder has.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Allows avformat_query_codec to be used to check for valid image2 encoders.
Reuses the existing ff_guess_image2_codec ID table.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This was an oversight when the IS system was being first implemented.
The ener01 part was largely a result of trial and error and the fact
that the sum of coef0 and coef1 could result in a zero was
overlooked. Once ener01 turns to zero it's used to divide the left
channel energy which doesn't turn out so well as it fills IS[]
with -nan's and inf's which in turn confused the quantize_band_cost.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
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>
Since PNS generates coefficients it doesn't make sense to send
the predicted ones as well. Also the specifications explicitly
state to disable right channel IS predictors.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
It's better to trust that the coefficients generated will be
closer than the coefficients derived, and the new PNS implementation
makes sure that this happens.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
The specifications explicitly state to use roundf() which
also rounds half-integer values away from zero.
This does fix a few IS artifacts.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
