avcodec/aarch64/aacencdsp: NEON implementation

This patch supplies handwritten NEON code for AAC.

The benchmarks below were collected by invoking these two commands on
each of my boards, A78, A72 and Thinkpad x13s:
1) ./tests/checkasm/checkasm --test=aacencdsp --bench --runs=12
2) ./ffmpeg -y -t 10:00 -f lavfi -i sine /tmp/foo.aac (the first line is
speed without the patch, second, with)

- A78
abs_pow34_c:                                          4161.5 ( 1.00x)
abs_pow34_neon:                                       3586.2 ( 1.16x)
quant_bands_signed_c:                                 5548.0 ( 1.00x)
quant_bands_signed_neon:                              1126.8 ( 4.92x)
quant_bands_unsigned_c:                               3979.2 ( 1.00x)
quant_bands_unsigned_neon:                             800.2 ( 4.97x)

size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed=71.6x
size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed=82.3x

- A72
abs_pow34_c:                                         15362.2 ( 1.00x)
abs_pow34_neon:                                      15382.5 ( 1.00x)
quant_bands_signed_c:                                 9926.5 ( 1.00x)
quant_bands_signed_neon:                              2467.8 ( 4.02x)
quant_bands_unsigned_c:                               5469.8 ( 1.00x)
quant_bands_unsigned_neon:                            2089.5 ( 2.62x)

size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed=34.3x
size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed=37.8

- x13s
abs_pow34_c:                                          2413.4 ( 1.00x)
abs_pow34_neon:                                       1796.2 ( 1.34x)
quant_bands_signed_c:                                 2968.9 ( 1.00x)
quant_bands_signed_neon:                               675.6 ( 4.39x)
quant_bands_unsigned_c:                               2311.9 ( 1.00x)
quant_bands_unsigned_neon:                             477.1 ( 4.85x)

size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed= 135x
size=    5251KiB time=00:10:00.00 bitrate=  71.7kbits/s speed= 159x

Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/aacencdsp.h

@@ -34,6 +34,7 @@ typedef struct AACEncDSPContext {
 
 void ff_aacenc_dsp_init_riscv(AACEncDSPContext *s);
 void ff_aacenc_dsp_init_x86(AACEncDSPContext *s);
+void ff_aacenc_dsp_init_aarch64(AACEncDSPContext *s);
 
 static inline void abs_pow34_v(float *out, const float *in, const int size)
 {
@@ -66,6 +67,8 @@ static inline void ff_aacenc_dsp_init(AACEncDSPContext *s)
     ff_aacenc_dsp_init_riscv(s);
 #elif ARCH_X86
     ff_aacenc_dsp_init_x86(s);
+#elif ARCH_AARCH64
+    ff_aacenc_dsp_init_aarch64(s);
 #endif
 }
 

libavcodec/aarch64/Makefile

@@ -19,6 +19,7 @@ OBJS-$(CONFIG_VP8DSP)                   += aarch64/vp8dsp_init_aarch64.o
 # decoders/encoders
 OBJS-$(CONFIG_AAC_DECODER)              += aarch64/aacpsdsp_init_aarch64.o \
                                            aarch64/sbrdsp_init_aarch64.o
+OBJS-$(CONFIG_AAC_ENCODER)              += aarch64/aacencdsp_init.o
 OBJS-$(CONFIG_DCA_DECODER)              += aarch64/synth_filter_init.o
 OBJS-$(CONFIG_OPUS_DECODER)             += aarch64/opusdsp_init.o
 OBJS-$(CONFIG_RV40_DECODER)             += aarch64/rv40dsp_init_aarch64.o
@@ -38,6 +39,7 @@ ARMV8-OBJS-$(CONFIG_VIDEODSP)           += aarch64/videodsp.o
 
 # subsystems
 NEON-OBJS-$(CONFIG_AAC_DECODER)         += aarch64/sbrdsp_neon.o
+NEON-OBJS-$(CONFIG_AAC_ENCODER)         += aarch64/aacencdsp_neon.o
 NEON-OBJS-$(CONFIG_AC3DSP)              += aarch64/ac3dsp_neon.o
 NEON-OBJS-$(CONFIG_FDCTDSP)             += aarch64/fdctdsp_neon.o
 NEON-OBJS-$(CONFIG_FMTCONVERT)          += aarch64/fmtconvert_neon.o

libavcodec/aarch64/aacencdsp_init.c

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025 Krzysztof Aleksander Pyrkosz
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+
+#include "libavutil/arm/cpu.h"
+#include "libavutil/attributes.h"
+#include "libavcodec/aacencdsp.h"
+
+void ff_abs_pow34_neon(float *out, const float *in, const int size);
+void ff_aac_quant_bands_neon(int *, const float *, const float *, int, int,
+                             int, const float, const float);
+
+av_cold void ff_aacenc_dsp_init_aarch64(AACEncDSPContext *s)
+{
+    int cpu_flags = av_get_cpu_flags();
+    if (!have_neon(cpu_flags)) return;
+
+    s->abs_pow34 = ff_abs_pow34_neon;
+    s->quant_bands = ff_aac_quant_bands_neon;
+}

libavcodec/aarch64/aacencdsp_neon.S

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2025 Krzysztof Aleksander Pyrkosz
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/aarch64/asm.S"
+
+function ff_abs_pow34_neon, export=1
+1:
+        ld1             {v0.4s}, [x1], #16
+        subs            w2, w2, #4
+        fabs            v0.4s, v0.4s
+        fsqrt           v2.4s, v0.4s
+        fmul            v0.4s, v2.4s, v0.4s
+        fsqrt           v0.4s, v0.4s
+        st1             {v0.4s}, [x0], #16
+        b.ne            1b
+        ret
+endfunc
+
+function ff_aac_quant_bands_neon, export=1
+        scvtf           s2, w5
+        dup             v1.4s, v1.s[0]
+        dup             v2.4s, v2.s[0]
+        cbz             w4, 0f
+        movi            v5.4s, 0x80, lsl #24
+.irp signed,1,0
+\signed:
+        ld1             {v3.4s}, [x2], #16
+        subs            w3, w3, #4
+        fmul            v3.4s, v3.4s, v0.s[0]
+.if \signed
+        ld1             {v4.4s}, [x1], #16
+.endif
+        fadd            v3.4s, v3.4s, v1.4s
+.if \signed
+        and             v4.16b, v4.16b, v5.16b
+.endif
+        fmin            v3.4s, v3.4s, v2.4s
+.if \signed
+        eor             v3.16b, v4.16b, v3.16b
+.endif
+        fcvtzs          v3.4s, v3.4s
+        st1             {v3.4s}, [x0], #16
+        b.ne            \signed\()b
+        ret
+.endr
+endfunc