Pixel Format descriptor, try #1.

(yes its intentionally unused, this is intended as a basis for further
 work, and to prevent repeation of the whole discussion dying and the
 results being forgotten)

Originally committed as revision 17548 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 91 insertions, 0 deletions

diff --git a/libavcodec/pixdesc.h b/libavcodec/pixdesc.h
new file mode 100644
index 0000000000..883ad5cd8c
--- /dev/null
+++ b/libavcodec/pixdesc.h
@@ -0,0 +1,91 @@
+/*
+ * Pixel Format descriptor
+ * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * 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 <inttypes.h>
+
+#include "libavutil/intreadwrite.h"
+
+typedef struct AVComponentDescriptor{
+    uint16_t plane        :2;            ///< which of the 4 planes contains the component
+    uint16_t step_minus1  :3;            ///< number of bytes between 2 horizontally consecutive pixels minus 1
+    uint16_t offset_plus1 :3;            ///< number of bytes before the component of the first pixel plus 1
+    uint16_t shift        :3;            ///< number of lsb that must be shifted away to get the value
+    uint16_t depth_minus1 :4;            ///< number of bits in the component minus 1
+}AVComponentDescriptor;
+
+typedef struct AVPixFmtDescriptor{
+    uint8_t nb_channels;        ///< The number of components each pixel has, (1-4)
+
+    /**
+     * Amount to shift the luma width right to find the chroma width, this is for
+     * example 1 for YV12
+     * chroma_width = -((-luma_width )>>log2_chroma_w)
+     * note above is needed to ensure rounding up
+     */
+    uint8_t log2_chroma_w;      ///< chroma_width = -((-luma_width )>>log2_chroma_w)
+
+    /**
+     * Amount to shift the luma height right to find the chroma height, this is for
+     * example 1 for YV12
+     * chroma_height= -((-luma_height)>>log2_chroma_h)
+     * note above is needed to ensure rounding up
+     */
+    uint8_t log2_chroma_h;
+    uint8_t flags;
+    AVComponentDescriptor comp[4]; ///< parameters that describes how pixels are packed
+}AVPixFmtDescriptor;
+
+#define PIX_FMT_BE        1 ///< Big endian
+#define PIX_FMT_PAL       2 ///< Pixel format has a palette i data[1], values are indexes in this palette
+#define PIX_FMT_BITSTREAM 4 ///< All values of a component are bitwise packed end to end
+
+
+static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4], AVPixFmtDescriptor *desc, int x, int y, int c, int w)
+{
+    AVComponentDescriptor comp= desc->comp[c];
+    int plane= comp.plane;
+    int depth= comp.depth_minus1+1;
+    int mask = (1<<depth)-1;
+    int shift= comp.shift;
+    int step = comp.step_minus1+1;
+    int flags= desc->flags;
+    const uint8_t *p= data[plane]+y*linesize[plane] + x * step + comp.offset_plus1 - 1;
+
+    //FIXME initial x in case of PIX_FMT_BITSTREAM is wrong
+
+    while(w--){
+        int val;
+        if(flags & PIX_FMT_BE) val= AV_RB16(p);
+        else                   val= AV_RL16(p);
+        val = (val>>shift) & mask;
+        if(flags & PIX_FMT_PAL)
+            val= data[1][4*val + c];
+        if(flags & PIX_FMT_BITSTREAM){
+            shift-=depth;
+            while(shift<0){
+                shift+=8;
+                p++;
+            }
+        }else
+            p+= step;
+        *dst++= val;
+    }
+}