On 17.04.2015 23:39, Luca Barbato wrote:
> On 17/04/15 16:08, Andreas Cadhalpun wrote:
>> On 17.04.2015 02:01, Luca Barbato wrote:
>>> is band->thr = 0.0f a valid value?
>>
>> Come to think of it, that's probably invalid.
I retract that, it seems band->thr = 0.0f is valid.
>> It can happen if coeffs[g].ath is not positive.
>
> ath() returns easily Inf and negative values...
It returns Inf for 0 and Inf, though that's not the
problem here. Neither is that it can return negative
values, because the minimum of the ath() function is
(or rather should be) subtracted:
coeffs[g].ath = minscale - minath;
The problem is that minath is not the minimum, only close:
minath = ath(3410, ATH_ADD) = -5.24237967
ath(3407, ATH_ADD) = -5.24241638
Attached patch is fixing this. With it the minimal value
of coeffs[g].ath is 0.0f.
>> Attached patch errors out in this case.
Scratch that patch. It shouldn't be negative (fixed with
attached patch), but 0.0f is possible.
>>> band->energy can be 0?
>>
>> Yes, it's set to 0.0f in calc_thr_3gpp if enough coefs are 0.
>
> and in that case the threshold? (that is calculated as a fraction of the
> energy at least in one place).
In that case band->thr is set to coeffs[g].ath:
band->thr_quiet = band->thr = FFMAX(band->thr, coeffs[g].ath);
So band->thr still can be 0.0f, i.e. the patch checking for (band->thr > 0.0f)
is still necessary.
Best regards,
Andreas
>From 667787601c17bd1d461f3171bedafd17214216e6 Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
Date: Sat, 18 Apr 2015 00:33:50 +0200
Subject: [PATCH] aacpsy: fix calculation of minath in psy_3gpp_init
The minimum of the ath(x, ATH_ADD) function is at 3407 (-5.24241638)
not at 3410 (-5.24237967).
Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
---
libavcodec/aacpsy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c
index 7205ee3..c9bcfaf 100644
--- a/libavcodec/aacpsy.c
+++ b/libavcodec/aacpsy.c
@@ -313,7 +313,7 @@ static av_cold int psy_3gpp_init(FFPsyContext *ctx) {
ctx->bitres.size = 6144 - pctx->frame_bits;
ctx->bitres.size -= ctx->bitres.size % 8;
pctx->fill_level = ctx->bitres.size;
- minath = ath(3410, ATH_ADD);
+ minath = ath(3407, ATH_ADD);
for (j = 0; j < 2; j++) {
AacPsyCoeffs *coeffs = pctx->psy_coef[j];
const uint8_t *band_sizes = ctx->bands[j];
--
2.1.4
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