Re: [FFmpeg-devel] [PATCH 2/2] swresample/resample: rework resample_one function to work the same way as the others

[Marton Balint <cus@passwd.hu>]

On Thu, 29 Feb 2024, Michael Niedermayer wrote:

> On Tue, Feb 27, 2024 at 10:48:10AM +0100, Marton Balint wrote:
>> Signed-off-by: Marton Balint <cus@passwd.hu>
>> ---
>>  libswresample/resample.c          | 29 +++++++----------------------
>>  libswresample/resample.h          |  4 ++--
>>  libswresample/resample_template.c | 14 ++++++++++++--
>>  3 files changed, 21 insertions(+), 26 deletions(-)
>>
>> diff --git a/libswresample/resample.c b/libswresample/resample.c
>> index 17cebad01b..89859dec79 100644
>> --- a/libswresample/resample.c
>> +++ b/libswresample/resample.c
>> @@ -356,26 +356,7 @@ static int multiple_resample(ResampleContext *c, AudioData *dst, int dst_size, A
>>
>>      *consumed = 0;
>>
>> -    if (c->filter_length == 1 && c->phase_count == 1) {
>> -        int64_t index2= (1LL<<32)*c->frac/c->src_incr + (1LL<<32)*c->index + 1;
>> -        int64_t incr= (1LL<<32) * c->dst_incr / c->src_incr + 1;
>> -        int new_size = (src_size * (int64_t)c->src_incr - c->frac + c->dst_incr - 1) / c->dst_incr;
>> -
>> -        dst_size = FFMAX(FFMIN(dst_size, new_size), 0);
>> -        if (dst_size > 0) {
>> -            for (i = 0; i < dst->ch_count; i++) {
>> -                c->dsp.resample_one(dst->ch[i], src->ch[i], dst_size, index2, incr);
>> -                if (i+1 == dst->ch_count) {
>> -                    c->index += dst_size * c->dst_incr_div;
>> -                    c->index += (c->frac + dst_size * (int64_t)c->dst_incr_mod) / c->src_incr;
>> -                    av_assert2(c->index >= 0);
>> -                    *consumed = c->index;
>> -                    c->frac   = (c->frac + dst_size * (int64_t)c->dst_incr_mod) % c->src_incr;
>> -                    c->index = 0;
>> -                }
>> -            }
>> -        }
>> -    } else {
>> +    {
>>          int64_t end_index = (1LL + src_size - c->filter_length) * c->phase_count;
>>          int64_t delta_frac = (end_index - c->index) * c->src_incr - c->frac;
>>          int delta_n = (delta_frac + c->dst_incr - 1) / c->dst_incr;
>> @@ -386,8 +367,12 @@ static int multiple_resample(ResampleContext *c, AudioData *dst, int dst_size, A
>>          if (dst_size > 0) {
>>              /* resample_linear and resample_common should have same behavior
>>               * when frac and dst_incr_mod are zero */
>> -            resample_func = (c->linear && (c->frac || c->dst_incr_mod)) ?
>> -                            c->dsp.resample_linear : c->dsp.resample_common;
>> +            if (c->filter_length == 1 && c->phase_count == 1)
>> +                resample_func = c->dsp.resample_one;
>> +            else if (c->linear && (c->frac || c->dst_incr_mod))
>> +                resample_func = c->dsp.resample_linear;
>> +            else
>> +                resample_func = c->dsp.resample_common;
>>              for (i = 0; i < dst->ch_count; i++)
>>                  *consumed = resample_func(c, dst->ch[i], src->ch[i], dst_size, i+1 == dst->ch_count);
>>          }
>> diff --git a/libswresample/resample.h b/libswresample/resample.h
>> index 1731dad3cf..8cc29effe8 100644
>> --- a/libswresample/resample.h
>> +++ b/libswresample/resample.h
>> @@ -51,8 +51,8 @@ typedef struct ResampleContext {
>>      int phase_count_compensation;      /* desired phase_count when compensation is enabled */
>>
>>      struct {
>> -        void (*resample_one)(void *dst, const void *src,
>> -                             int n, int64_t index, int64_t incr);
>> +        int (*resample_one)(struct ResampleContext *c, void *dst,
>> +                            const void *src, int n, int update_ctx);
>>          int (*resample_common)(struct ResampleContext *c, void *dst,
>>                                 const void *src, int n, int update_ctx);
>>          int (*resample_linear)(struct ResampleContext *c, void *dst,
>> diff --git a/libswresample/resample_template.c b/libswresample/resample_template.c
>> index 4c227b9940..a8114ea918 100644
>> --- a/libswresample/resample_template.c
>> +++ b/libswresample/resample_template.c
>> @@ -72,17 +72,27 @@
>>
>>  #endif
>>
>> -static void RENAME(resample_one)(void *dest, const void *source,
>> -                                 int dst_size, int64_t index2, int64_t incr)
>> +static int RENAME(resample_one)(ResampleContext *c,
>> +                                void *dest, const void *source,
>> +                                int dst_size, int update_ctx)
>>  {
>>      DELEM *dst = dest;
>>      const DELEM *src = source;
>>      int dst_index;
>
>> +    int64_t index2 = (1LL << 32) * c->frac     / c->src_incr + 1 + (1LL << 32) * c->index;
>> +    int64_t incr   = (1LL << 32) * c->dst_incr / c->src_incr + 1;
>
> This computation is done repeatedly for each channel, thats not needed
> its enough if its done once

I consider that negligable for real cases, and it makes the code cleaner 
doing the computations here.

If you insist on this, then it is better to rework all the resample funcs 
to work on all channels in a separate patch.

Regards,
Marton
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