lavc/opusdsp: RISC-V V (128-bit) postfilter

This is implemented for a vector size of 128-bit. Since the scalar
product in the inner loop covers 5 samples or 160 bits, we need a group
multipler of 2.

To avoid reconfiguring the vector type, the outer loop, which loads
multiple input samples sticks to the same multipler. Consequently, the
outer loop loads 8 samples per iteration. This is safe since the minimum
period of the CELT codec is 15 samples.

The same code would also work, albeit needlessly inefficiently with a
vector length of 256 bits. A proper implementation will follow instead.

1 files changed, 42 insertions, 0 deletions

diff --git a/libavcodec/riscv/opusdsp_init.c b/libavcodec/riscv/opusdsp_init.c
new file mode 100644
index 0000000000..ca58bb4039
--- /dev/null
+++ b/libavcodec/riscv/opusdsp_init.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright © 2022 Rémi Denis-Courmont.
+ *
+ * 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/attributes.h"
+#include "libavutil/cpu.h"
+#include "libavutil/riscv/cpu.h"
+#include "libavcodec/opusdsp.h"
+
+void ff_opus_postfilter_rvv_128(float *data, int period, float *g, int len);
+
+av_cold void ff_opus_dsp_init_riscv(OpusDSP *d)
+{
+#if HAVE_RVV
+    int flags = av_get_cpu_flags();
+
+    if (flags & AV_CPU_FLAG_RVV_F32)
+        switch (ff_get_rv_vlenb()) {
+        case 16:
+            d->postfilter = ff_opus_postfilter_rvv_128;
+            break;
+        }
+#endif
+}