Re: [FFmpeg-devel] [PATCH v2 2/2] checkasm: aacencdsp: Actually test nonzero values in quant_bands

["Martin Storsjö" <martin@martin.st>]

On Fri, 7 Feb 2025, Martin Storsjö wrote:

> On Wed, 5 Feb 2025, Martin Storsjö wrote:
>
>> Previously, we read elements from ff_aac_pow34sf_tab; however
>> that table is initialized to zero; one needs to call
>> ff_aac_float_common_init() to make sure that the table is
>> initialized.
>> 
>> However, given the range of the input values, a large number of
>> entries in ff_aac_pow34sf_tab would give results outside of the
>> range for signed 32 bit integers. As the largest aac_cb_maxval
>> entry is 16, it seems more reasonable to produce values within
>> an order of mangitude of that value.
>> 
>> (When hitting INT_MIN, implementations may end up with different
>> results depending on whether the value is negated as a float or
>> as an int. This corner case is irrelevant in practice as this
>> is way outside of the expected value range here.)
>> 
>> Coincidentally, this fixes linking checkasm with Apple's older
>> linker. (In Xcode 15, Apple switched to a new linker. The one in
>> older toolchains seems to have a bug where it won't figure out to
>> load object files from a static library, if the only symbol
>> referenced in the object file is a "common" symbol, i.e. one for
>> a zero-initialized variable. This issue can also be reproduced with
>> newer Apple toolchains by passing -Wl,-ld_classic to the linker.)
>> ---
>> tests/checkasm/aacencdsp.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/tests/checkasm/aacencdsp.c b/tests/checkasm/aacencdsp.c
>> index 5308a2ac03..713284211c 100644
>> --- a/tests/checkasm/aacencdsp.c
>> +++ b/tests/checkasm/aacencdsp.c
>> @@ -67,7 +67,7 @@ static void test_abs_pow34(AACEncDSPContext *s)
>> static void test_quant_bands(AACEncDSPContext *s)
>> {
>>     int maxval = randomize_elem(aac_cb_maxval);
>> -    float q34 = randomize_elem(ff_aac_pow34sf_tab);
>> +    float q34 = (float)rnd() / (UINT_MAX / 1024);
>>     float rounding = (rnd() & 1) ? ROUND_TO_ZERO : ROUND_STANDARD;
>>     LOCAL_ALIGNED_16(float, in, [BUF_SIZE]);
>>     LOCAL_ALIGNED_16(float, scaled, [BUF_SIZE]);
>> -- 
>> 2.43.0
>
> These changes were OK'd by Lynne on irc, I'll push them later if there's no 
> more feedback on it. (I've tested these changes with thousands of different 
> checkasm seeds now.)

Pushed now.

// Martin
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