1 files changed, 135 insertions, 0 deletions
diff --git a/libavcodec/vpx_rac.h b/libavcodec/vpx_rac.h
new file mode 100644
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+++ b/libavcodec/vpx_rac.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2006  Aurelien Jacobs <aurel@gnuage.org>
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * Common VP5-VP9 range decoder stuff
+ */
+
+#ifndef AVCODEC_VPX_RAC_H
+#define AVCODEC_VPX_RAC_H
+
+#include <stdint.h>
+
+#include "config.h"
+#include "libavutil/attributes.h"
+#include "bytestream.h"
+
+typedef struct VPXRangeCoder {
+    int high;
+    int bits; /* stored negated (i.e. negative "bits" is a positive number of
+                 bits left) in order to eliminate a negate in cache refilling */
+    const uint8_t *buffer;
+    const uint8_t *end;
+    unsigned int code_word;
+    int end_reached;
+} VPXRangeCoder;
+
+extern const uint8_t ff_vpx_norm_shift[256];
+int ff_vpx_init_range_decoder(VPXRangeCoder *c, const uint8_t *buf, int buf_size);
+
+/**
+ * returns 1 if the end of the stream has been reached, 0 otherwise.
+ */
+static av_always_inline int vpx_rac_is_end(VPXRangeCoder *c)
+{
+    if (c->end <= c->buffer && c->bits >= 0)
+        c->end_reached ++;
+    return c->end_reached > 10;
+}
+
+static av_always_inline unsigned int vpx_rac_renorm(VPXRangeCoder *c)
+{
+    int shift = ff_vpx_norm_shift[c->high];
+    int bits = c->bits;
+    unsigned int code_word = c->code_word;
+
+    c->high   <<= shift;
+    code_word <<= shift;
+    bits       += shift;
+    if(bits >= 0 && c->buffer < c->end) {
+        code_word |= bytestream_get_be16(&c->buffer) << bits;
+        bits -= 16;
+    }
+    c->bits = bits;
+    return code_word;
+}
+
+#if   ARCH_ARM
+#include "arm/vpx_arith.h"
+#elif ARCH_X86
+#include "x86/vpx_arith.h"
+#endif
+
+#ifndef vpx_rac_get_prob
+#define vpx_rac_get_prob vpx_rac_get_prob
+static av_always_inline int vpx_rac_get_prob(VPXRangeCoder *c, uint8_t prob)
+{
+    unsigned int code_word = vpx_rac_renorm(c);
+    unsigned int low = 1 + (((c->high - 1) * prob) >> 8);
+    unsigned int low_shift = low << 16;
+    int bit = code_word >= low_shift;
+
+    c->high = bit ? c->high - low : low;
+    c->code_word = bit ? code_word - low_shift : code_word;
+
+    return bit;
+}
+#endif
+
+#ifndef vpx_rac_get_prob_branchy
+// branchy variant, to be used where there's a branch based on the bit decoded
+static av_always_inline int vpx_rac_get_prob_branchy(VPXRangeCoder *c, int prob)
+{
+    unsigned long code_word = vpx_rac_renorm(c);
+    unsigned low = 1 + (((c->high - 1) * prob) >> 8);
+    unsigned low_shift = low << 16;
+
+    if (code_word >= low_shift) {
+        c->high     -= low;
+        c->code_word = code_word - low_shift;
+        return 1;
+    }
+
+    c->high = low;
+    c->code_word = code_word;
+    return 0;
+}
+#endif
+
+static av_always_inline int vpx_rac_get(VPXRangeCoder *c)
+{
+    unsigned int code_word = vpx_rac_renorm(c);
+    /* equiprobable */
+    int low = (c->high + 1) >> 1;
+    unsigned int low_shift = low << 16;
+    int bit = code_word >= low_shift;
+    if (bit) {
+        c->high   -= low;
+        code_word -= low_shift;
+    } else {
+        c->high = low;
+    }
+
+    c->code_word = code_word;
+    return bit;
+}
+
+#endif /* AVCODEC_VPX_RAC_H */