Re: [FFmpeg-devel] [PATCH 1/4] avcodec/snow: Move ff_snow_inner_add_yblock() to snow_dwt.c

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> On Mon, Sep 19, 2022 at 11:27:49PM +0200, Andreas Rheinhardt wrote:
>> Only used there and by x86 snow asm code as fallback.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
>> ---
>>  libavcodec/snow.c     | 33 ---------------------------------
>>  libavcodec/snow.h     |  3 ---
>>  libavcodec/snow_dwt.c | 32 ++++++++++++++++++++++++++++++++
>>  libavcodec/snow_dwt.h |  3 +++
>>  4 files changed, 35 insertions(+), 36 deletions(-)
>>
>> diff --git a/libavcodec/snow.c b/libavcodec/snow.c
>> index aa15fccc42..85ad6d10a1 100644
>> --- a/libavcodec/snow.c
>> +++ b/libavcodec/snow.c
>> @@ -29,39 +29,6 @@
>>  #include "snowdata.h"
>>  
>>  
>> -void ff_snow_inner_add_yblock(const uint8_t *obmc, const int obmc_stride, uint8_t * * block, int b_w, int b_h,
>> -                              int src_x, int src_y, int src_stride, slice_buffer * sb, int add, uint8_t * dst8){
>> -    int y, x;
>> -    IDWTELEM * dst;
>> -    for(y=0; y<b_h; y++){
>> -        //FIXME ugly misuse of obmc_stride
>> -        const uint8_t *obmc1= obmc + y*obmc_stride;
>> -        const uint8_t *obmc2= obmc1+ (obmc_stride>>1);
>> -        const uint8_t *obmc3= obmc1+ obmc_stride*(obmc_stride>>1);
>> -        const uint8_t *obmc4= obmc3+ (obmc_stride>>1);
>> -        dst = slice_buffer_get_line(sb, src_y + y);
>> -        for(x=0; x<b_w; x++){
>> -            int v=   obmc1[x] * block[3][x + y*src_stride]
>> -                    +obmc2[x] * block[2][x + y*src_stride]
>> -                    +obmc3[x] * block[1][x + y*src_stride]
>> -                    +obmc4[x] * block[0][x + y*src_stride];
>> -
>> -            v <<= 8 - LOG2_OBMC_MAX;
>> -            if(FRAC_BITS != 8){
>> -                v >>= 8 - FRAC_BITS;
>> -            }
>> -            if(add){
>> -                v += dst[x + src_x];
>> -                v = (v + (1<<(FRAC_BITS-1))) >> FRAC_BITS;
>> -                if(v&(~255)) v= ~(v>>31);
>> -                dst8[x + y*src_stride] = v;
>> -            }else{
>> -                dst[x + src_x] -= v;
>> -            }
>> -        }
>> -    }
>> -}
>> -
>>  int ff_snow_get_buffer(SnowContext *s, AVFrame *frame)
>>  {
>>      int ret, i;
>> diff --git a/libavcodec/snow.h b/libavcodec/snow.h
>> index ed0f9abb42..1c976b9ba7 100644
>> --- a/libavcodec/snow.h
>> +++ b/libavcodec/snow.h
>> @@ -45,11 +45,8 @@
>>  #define QSHIFT 5
>>  #define QROOT (1<<QSHIFT)
>>  #define LOSSLESS_QLOG -128
>> -#define FRAC_BITS 4
>>  #define MAX_REF_FRAMES 8
>>  
>> -#define LOG2_OBMC_MAX 8
>> -#define OBMC_MAX (1<<(LOG2_OBMC_MAX))
>>  typedef struct BlockNode{
>>      int16_t mx;                 ///< Motion vector component X, see mv_scale
>>      int16_t my;                 ///< Motion vector component Y, see mv_scale
>> diff --git a/libavcodec/snow_dwt.c b/libavcodec/snow_dwt.c
>> index 18b315ef66..9401d119d0 100644
>> --- a/libavcodec/snow_dwt.c
>> +++ b/libavcodec/snow_dwt.c
>> @@ -25,6 +25,38 @@
>>  #include "me_cmp.h"
>>  #include "snow_dwt.h"
>>  
>> +void ff_snow_inner_add_yblock(const uint8_t *obmc, const int obmc_stride,
>> +                              uint8_t **block, int b_w, int b_h,
>> +                              int src_x, int src_y, int src_stride,
>> +                              slice_buffer * sb, int add, uint8_t * dst8)
>> +{
>> +    for (int y = 0; y < b_h; y++) {
>> +        //FIXME ugly misuse of obmc_stride
>> +        const uint8_t *obmc1 = obmc  + y * obmc_stride;
>> +        const uint8_t *obmc2 = obmc1 + (obmc_stride >> 1);
>> +        const uint8_t *obmc3 = obmc1 + obmc_stride * (obmc_stride >> 1);
>> +        const uint8_t *obmc4 = obmc3 + (obmc_stride >> 1);
>> +        IDWTELEM *dst = slice_buffer_get_line(sb, src_y + y);
>> +        for (int x = 0; x < b_w; x++) {
>> +            int v = obmc1[x] * block[3][x + y*src_stride]
>> +                  + obmc2[x] * block[2][x + y*src_stride]
>> +                  + obmc3[x] * block[1][x + y*src_stride]
>> +                  + obmc4[x] * block[0][x + y*src_stride];
>> +
>> +            v <<= 8 - LOG2_OBMC_MAX;
>> +            if (FRAC_BITS != 8)
>> +                v >>= 8 - FRAC_BITS;
>> +            if (add) {
>> +                v += dst[x + src_x];
>> +                v = (v + (1 << (FRAC_BITS - 1))) >> FRAC_BITS;
>> +                if (v & (~255)) v= ~(v>>31);
>> +                dst8[x + y*src_stride] = v;
>> +            } else
>> +                dst[x + src_x] -= v;
>> +        }
>> +    }
>> +}
>> +
> 
> putting this in snow_dwt may be convenient but it is not part of the dwt so
> this feels semantically wrong
> 

If it is not part of the dwt, then why does SnowDWTContext have an
inner_add_yblock function pointer whose C version is
ff_snow_inner_add_yblock?

- Andreas
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