[FFmpeg-devel] [PATCH 5/5] aarch64/opusdsp: implement NEON accerelated postfilter and deemphasis

Carl Eugen Hoyos ceffmpeg at gmail.com
Sat Mar 23 17:04:56 EET 2019


2019-03-23 15:23 GMT+01:00, Lynne <dev at lynne.ee>:
> 16 Mar 2019, 16:34 by dev at lynne.ee:
>
>> 153372 UNITS in postfilter_c,   65536 runs,      0 skips
>> 73164 UNITS in postfilter_neon,   65536 runs,      0 skips -> 2.1x speedup
>>
>> 80591 UNITS in deemphasis_c,  131072 runs,      0 skips
>> 43969 UNITS in deemphasis_neon,  131072 runs,      0 skips -> 1.83x
>> speedup
>>
>> Total decoder speedup: ~15% on a Raspberry Pi 3 (from 28.1x to 33.5x
>> realtime)
>>
>> Deemphasis SIMD based on the following unrolling:
>> const float c1 = CELT_EMPH_COEFF, c2 = c1*c1, c3 = c2*c1, c4 = c3*c1;
>> float state = coeff;
>>
>> for (int i = 0; i < len; i += 4) {
>>     y[0] = x[0] + c1*state;
>>     y[1] = x[1] + c2*state + c1*x[0];
>>     y[2] = x[2] + c3*state + c1*x[1] + c2*x[0];
>>     y[3] = x[3] + c4*state + c1*x[2] + c2*x[1] + c3*x[0];
>>
>>     state = y[3];
>>     y += 4;
>>     x += 4;
>> }
>>
>> Unlike the x86 version, duplication is used instead of pslldq so
>> the structure and tables are different.
>> Same approach tested on x86 (3x pslldq -> vbroadcastss + shufps + pslldq)
>> had the same performance, so 3x pslldq was kept as vbroadcastss has a
>> higher latency.
>
> Could someone review the patches?

Which toolchains did you test?
(For compilation, not performance.)

Carl Eugen


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