lavc: APV decoder

libavcodec/apv_decode.h

@@ -0,0 +1,80 @@
+/*
+ * 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
+ */
+
+#ifndef AVCODEC_APV_DECODE_H
+#define AVCODEC_APV_DECODE_H
+
+#include <stdint.h>
+
+#include "apv.h"
+#include "avcodec.h"
+#include "get_bits.h"
+
+
+// Number of bits in the entropy look-up tables.
+// It may be desirable to tune this per-architecture, as a larger LUT
+// trades greater memory use for fewer instructions.
+// (N bits -> 24*2^N bytes of tables; 9 -> 12KB of tables.)
+#define APV_VLC_LUT_BITS 9
+#define APV_VLC_LUT_SIZE (1 << APV_VLC_LUT_BITS)
+
+typedef struct APVVLCLUTEntry {
+    uint16_t result;  // Return value if not reading more.
+    uint8_t  consume; // Number of bits to consume.
+    uint8_t  more;    // Whether to read additional bits.
+} APVVLCLUTEntry;
+
+typedef struct APVVLCLUT {
+    APVVLCLUTEntry lut[6][APV_VLC_LUT_SIZE];
+} APVVLCLUT;
+
+typedef struct APVEntropyState {
+    void *log_ctx;
+
+    const APVVLCLUT *decode_lut;
+
+    int16_t prev_dc;
+    int16_t prev_dc_diff;
+    int16_t prev_1st_ac_level;
+} APVEntropyState;
+
+
+/**
+ * Build the decoder VLC look-up table.
+ */
+void ff_apv_entropy_build_decode_lut(APVVLCLUT *decode_lut);
+
+/**
+ * Entropy decode a single 8x8 block to coefficients.
+ *
+ * Outputs in block order (dezigzag already applied).
+ */
+int ff_apv_entropy_decode_block(int16_t *coeff,
+                                GetBitContext *gbc,
+                                APVEntropyState *state);
+
+/**
+ * Read a single APV VLC code.
+ *
+ * This entrypoint is exposed for testing.
+ */
+unsigned int ff_apv_read_vlc(GetBitContext *gbc, int k_param,
+                             const APVVLCLUT *lut);
+
+
+#endif /* AVCODEC_APV_DECODE_H */