avcodec: add avdct

This provides a public sustainable API/ABI for DCT functions.
Only externally used dct functions are included.
The structure is extensible without ABI issues compared to the
existing dct contexts.

See Mailing list and IRC log of 2014-07-26/27

Reviewed-by: ubitux
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 76 insertions, 0 deletions

diff --git a/libavcodec/avdct.h b/libavcodec/avdct.h
new file mode 100644
index 0000000000..4d691e013d
--- /dev/null
+++ b/libavcodec/avdct.h
@@ -0,0 +1,76 @@
+/*
+ * 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_AVDCT_H
+#define AVCODEC_AVDCT_H
+
+#include "libavutil/opt.h"
+
+/**
+ * AVDCT context.
+ * @note function pointers can be NULL if the specific features have been
+ *       disabled at build time.
+ */
+typedef struct AVDCT {
+    const AVClass *av_class;
+
+    void (*idct)(int16_t *block /* align 16 */);
+
+    /**
+     * IDCT input permutation.
+     * Several optimized IDCTs need a permutated input (relative to the
+     * normal order of the reference IDCT).
+     * This permutation must be performed before the idct_put/add.
+     * Note, normally this can be merged with the zigzag/alternate scan<br>
+     * An example to avoid confusion:
+     * - (->decode coeffs -> zigzag reorder -> dequant -> reference IDCT -> ...)
+     * - (x -> reference DCT -> reference IDCT -> x)
+     * - (x -> reference DCT -> simple_mmx_perm = idct_permutation
+     *    -> simple_idct_mmx -> x)
+     * - (-> decode coeffs -> zigzag reorder -> simple_mmx_perm -> dequant
+     *    -> simple_idct_mmx -> ...)
+     */
+    uint8_t idct_permutation[64];
+
+    void (*fdct)(int16_t *block /* align 16 */);
+
+
+    /**
+     * DCT algorithm.
+     * must use AVOptions to set this field.
+     */
+    int dct_algo;
+
+    /**
+     * IDCT algorithm.
+     * must use AVOptions to set this field.
+     */
+    int idct_algo;
+} AVDCT;
+
+/**
+ * Allocates a AVDCT context.
+ * This needs to be initialized with avcodec_dct_init() after optionally
+ * configuring it with AVOptions.
+ *
+ * To free it use av_free()
+ */
+AVDCT *avcodec_dct_alloc(void);
+int avcodec_dct_init(AVDCT *);
+
+#endif /* AVCODEC_AVDCT_H */