Re: [FFmpeg-devel] [PATCH] checkasm: h264dsp: test luma_dc_dequant

["Martin Storsjö" <martin@martin.st>]

On Fri, 13 Jun 2025, Tristan Matthews wrote:

> On Thu, Jun 12, 2025 at 4:14 PM Martin Storsjö <martin@martin.st> wrote:
>>
>> On Thu, 12 Jun 2025, Tristan Matthews wrote:
>>
>>> ---
>>> tests/checkasm/h264dsp.c | 37 +++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 37 insertions(+)
>>>
>>> diff --git a/tests/checkasm/h264dsp.c b/tests/checkasm/h264dsp.c
>>> index d1228ed985..5fba31cf69 100644
>>> --- a/tests/checkasm/h264dsp.c
>>> +++ b/tests/checkasm/h264dsp.c
>>> @@ -22,6 +22,7 @@
>>> #include "checkasm.h"
>>> #include "libavcodec/h264dsp.h"
>>> #include "libavcodec/h264data.h"
>>> +#include "libavcodec/h264idct.h"
>>> #include "libavcodec/h264_parse.h"
>>> #include "libavutil/common.h"
>>> #include "libavutil/intreadwrite.h"
>>> @@ -324,6 +325,41 @@ static void check_idct_multiple(void)
>>>     }
>>> }
>>>
>>> +static void check_idct_dequant(void)
>>> +{
>>> +    static const int depths[5] = { 8, 9, 10, 12, 14 };
>>> +    LOCAL_ALIGNED_16(int16_t, src, [16]);
>>> +    LOCAL_ALIGNED_16(int16_t, dst0, [16 * 16]);
>>> +    LOCAL_ALIGNED_16(int16_t, dst1, [16 * 16]);
>>> +    H264DSPContext h;
>>> +    int bit_depth, i, qmul;
>>> +    declare_func_emms(AV_CPU_FLAG_MMX | AV_CPU_FLAG_SSE2, void, int16_t *output, int16_t *input, int qmul);
>>> +
>>> +    for (int j = 0; j < 16; j++)
>>> +        src[j] = (rnd() % 512) - 256;
>>> +
>>> +    qmul = rnd() % 4096;
>>> +
>>> +    memset(dst0, 0, 16 * 16 * sizeof(dst0[0]));
>>> +    memset(dst1, 0, 16 * 16 * sizeof(dst1[0]));
>>> +
>>> +    for (i = 0; i < FF_ARRAY_ELEMS(depths); i++) {
>>> +        bit_depth = depths[i];
>>> +        ff_h264dsp_init(&h, bit_depth, 1);
>>> +
>>> +        if (check_func(h.h264_luma_dc_dequant_idct, "h264_luma_dc_dequant_idct_%d", bit_depth)) {
>>> +
>>> +            call_ref(dst0, src, qmul);
>>> +            call_new(dst1, src, qmul);
>>> +
>>> +            if (memcmp(dst0, dst1, 16 * 16 * sizeof(*dst0)))
>>> +                fail();
>>
>> If possible, use the checkasm_check_*() helpers for validation for new
>> code; this gives you printout of the differing values if you run "checkasm
>> -v" and more. In this case, I think checkasm_check(int16_t, dst0,
>> 16*sizeof(int16_t), dst1, 16*sizeof(int16_t), 16, 16, "dst") would be
>> suitable one.
>
> Good catch, also I realized that the output buffers were too small,
> will be fixed in the next version.

Why was that too small? If we write (and check) 16x16 int16_t elements, 
the previous allocation of LOCAL_ALIGNED_16(int16_t, dst0, [16 * 16]) 
sounds just right? Or does the function use the [16*16,2*16*16) area of 
the destination as scratch space?

// Martin
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