For #1659, #307, add ffmpeg-4.2-fit for rtc

trunk/3rdparty/ffmpeg-4.2-fit/libavcodec/opusdsp.c

@@ -0,0 +1,67 @@
+/*
+ * 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 "opusdsp.h"
+
+static void postfilter_c(float *data, int period, float *gains, int len)
+{
+    const float g0 = gains[0];
+    const float g1 = gains[1];
+    const float g2 = gains[2];
+
+    float x4 = data[-period - 2];
+    float x3 = data[-period - 1];
+    float x2 = data[-period + 0];
+    float x1 = data[-period + 1];
+
+    for (int i = 0; i < len; i++) {
+        float x0 = data[i - period + 2];
+        data[i] += g0 * x2        +
+                   g1 * (x1 + x3) +
+                   g2 * (x0 + x4);
+        x4 = x3;
+        x3 = x2;
+        x2 = x1;
+        x1 = x0;
+    }
+}
+
+static float deemphasis_c(float *y, float *x, float coeff, int len)
+{
+    float state = coeff;
+
+    for (int i = 0; i < len; i++) {
+        const float tmp = x[i] + state;
+        state = tmp * CELT_EMPH_COEFF;
+        y[i] = tmp;
+    }
+
+    return state;
+}
+
+av_cold void ff_opus_dsp_init(OpusDSP *ctx)
+{
+    ctx->postfilter = postfilter_c;
+    ctx->deemphasis = deemphasis_c;
+
+    if (ARCH_X86)
+        ff_opus_dsp_init_x86(ctx);
+
+    if (ARCH_AARCH64)
+        ff_opus_dsp_init_aarch64(ctx);
+}