Initial decoder implementation.

With minor contributions from:
 - Jean-Baptiste Kempf <jb@videolan.org>
 - Marvin Scholz <epirat07@gmail.com>
 - Hugo Beauzée-Luyssen <hugo@videolan.org>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/msac.h b/src/msac.h
new file mode 100644
index 0000000..8e61b5c
--- /dev/null
+++ b/src/msac.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2001-2016, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+
+#ifndef __DAV1D_SRC_MSAC_H__
+#define __DAV1D_SRC_MSAC_H__
+
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct MsacContext {
+    const uint8_t *buf, *end, *bptr;
+    int32_t tell_offs;
+    uint32_t dif;
+    uint16_t rng;
+    int16_t cnt;
+    int error;
+} MsacContext;
+
+void msac_init(MsacContext *c, const uint8_t *data, size_t sz);
+unsigned msac_decode_symbol(MsacContext *c, const uint16_t *cdf,
+                            const unsigned n_symbols);
+unsigned msac_decode_bool(MsacContext *c, unsigned cdf);
+unsigned msac_decode_bools(MsacContext *c, unsigned l);
+int msac_decode_subexp(MsacContext *c, int ref, unsigned n, unsigned k);
+int msac_decode_uniform(MsacContext *c, unsigned n);
+void update_cdf(uint16_t *cdf, unsigned val, unsigned nsymbs);
+
+static inline unsigned msac_decode_symbol_adapt(MsacContext *const c,
+                                                uint16_t *const cdf,
+                                                const unsigned n_symbols)
+{
+    const unsigned val = msac_decode_symbol(c, cdf, n_symbols);
+    update_cdf(cdf, val, n_symbols);
+    return val;
+}
+
+static inline unsigned msac_decode_bool_adapt(MsacContext *const c,
+                                              uint16_t *const cdf)
+{
+    const unsigned bit = msac_decode_bool(c, *cdf);
+    uint16_t bak_cdf[3] = { cdf[0], 0, cdf[1] };
+    update_cdf(bak_cdf, bit, 2);
+    cdf[0] = bak_cdf[0];
+    cdf[1] = bak_cdf[2];
+    return bit;
+}
+
+#endif /* __DAV1D_SRC_MSAC_H__ */