[MPlayer-dev-eng] Open Source Video 1 Decoder

Mike Melanson melanson at pcisys.net
Sun Nov 11 10:32:02 CET 2001


Hi there,
	I'm pleased to contribute an open source decoder for
Microsoft Video 1 data. This is data that corresponds to the CRAM, WHAM,
and MSVC fourccs, and is normally handled by the msvidc32.dll codec. The
16-bit variant works just fine, but the 8-bit variant is still slightly
off. If anyone has some more 8-bit Video 1 files, or 16-bit ones that
don't work, send them my way.

	Please note that this is my first attempt at making a patch
file. I think it should patch onto the current CVS version using
  patch -p6 < video1.patches
And this is what my codecs.conf entry looks like:
;videocodec cram
videocodec video1
  info "Microsoft Video 1"
  status working
  fourcc cram,CRAM
  fourcc msvc,MSVC
  fourcc wham,WHAM
  driver video1
  out BGR24

	You'll probably want to move the decoder into a separate file so
it doesn't clutter up dec_video.c. And you may want to fix up the
little-endian reader/converters as well; I just used my own since I didn't
know what to use from the MPlayer codebase. Oh, and I was also lazy to the
point of only implementing BGR888 output data.

	I was able to implement this by studying the XAnim source
code. For those who may be worried about code origin issues, I didn't
copy this code directly from XAnim. I reverse engineered a high-level
description of the algorithm that you can read here:
  http://www.pcisys.net/~melanson/video1.txt
I wrote my implementation based on that description. I like to think that
my decoder is slightly more elegant than XAnim's.

	Hopefully, this code will eliminate the need for at least one
binary-only codec. It's a start.
-- 
	-Mike Melanson

-------------- next part --------------
--- ../../../ppc/mplayer-cvs/main/codec-cfg.h	Tue Oct 23 08:01:13 2001
+++ codec-cfg.h	Sat Nov 10 10:59:51 2001
@@ -42,6 +42,7 @@
 #define VFM_RAW 8
 #define VFM_RLE 9
 #define VFM_XANIM 10
+#define VFM_VIDEO1 11
 
 #ifndef GUID_TYPE
 #define GUID_TYPE
--- ../../../ppc/mplayer-cvs/main/codec-cfg.c	Sun Nov  4 07:00:53 2001
+++ codec-cfg.c	Sat Nov 10 10:59:38 2001
@@ -223,6 +223,7 @@
 		"raw",
 		"rle",
 		"xanim",
+		"video1",
 		NULL
 	};
         char **drv=audioflag?audiodrv:videodrv;
--- ../../../ppc/mplayer-cvs/main/dec_video.c	Sat Nov 10 07:52:05 2001
+++ dec_video.c	Sun Nov 11 02:15:12 2001
@@ -86,6 +86,23 @@
 void AVI_Decode_RLE8(char *image,char *delta,int tdsize,
     unsigned int *map,int imagex,int imagey,unsigned char x11_bytes_pixel);
 
+void AVI_Decode_Video1_16(
+  char *encoded,
+  int encoded_size,
+  char *decoded,
+  int width,
+  int height,
+  int bytes_per_pixel);
+
+void AVI_Decode_Video1_8(
+  char *encoded,
+  int encoded_size,
+  char *decoded,
+  int width,
+  int height,
+  unsigned char *palette_map,
+  int bytes_per_pixel);
+
 //**************************************************************************//
 //             The OpenDivX stuff:
 //**************************************************************************//
@@ -251,7 +268,7 @@
 switch(sh_video->codec->driver){
  case VFM_XANIM: {
 #ifdef USE_XANIM
-   int ret=xacodec_init_video(sh_video,out_fmt);
+	   int ret=xacodec_init_video(sh_video,out_fmt);
    if(!ret) return 0;
 #else
 //   mp_msg(MSGT_DECVIDEO, MSGL_ERR, MSGTR_NoXAnimSupport);
@@ -450,6 +467,12 @@
      }
    }
    break;
+ case VFM_VIDEO1: {
+   int bpp=((out_fmt&255)+7)/8; // RGB only
+   sh_video->our_out_buffer = 
+     (char*)memalign(64, sh_video->disp_w*sh_video->disp_h*bpp); // FIXME!!!
+   }
+   break;
  }
 }
   sh_video->inited=1;
@@ -681,6 +704,19 @@
       sh_video->disp_w,sh_video->disp_h,((out_fmt&255)+7)/8);
     blit_frame=3;
     break;
+  case VFM_VIDEO1:
+    if (sh_video->bih->biBitCount == 16)
+      AVI_Decode_Video1_16(
+        start, in_size, sh_video->our_out_buffer,
+        sh_video->disp_w, sh_video->disp_h,
+        ((out_fmt&255)+7)/8);
+    else
+      AVI_Decode_Video1_8(
+        start, in_size, sh_video->our_out_buffer,
+        sh_video->disp_w, sh_video->disp_h,
+        (char *)sh_video->bih+40, ((out_fmt&255)+7)/8);
+    blit_frame = 3;
+    break;
 } // switch
 //------------------------ frame decoded. --------------------
 
@@ -726,4 +762,355 @@
 
   return blit_frame;
 }
+
+#define LE_16(x) *(unsigned short *)(x)
+
+#define DECODE_BGR555_TO_BGR888(x) \
+        x.c1_b = (x.c1 >> 7) & 0xF8; \
+        x.c1_g = (x.c1 >> 2) & 0xF8; \
+        x.c1_r = (x.c1 << 3) & 0xF8; \
+        x.c2_b = (x.c2 >> 7) & 0xF8; \
+        x.c2_g = (x.c2 >> 2) & 0xF8; \
+        x.c2_r = (x.c2 << 3) & 0xF8;
+
+#define DECODE_PALETTE_TO_BGR888(x) \
+        x.c1_b = palette_map[x.c1 * 4 + 2]; \
+        x.c1_g = palette_map[x.c1 * 4 + 1]; \
+        x.c1_r = palette_map[x.c1 * 4 + 0]; \
+        x.c2_b = palette_map[x.c2 * 4 + 2]; \
+        x.c2_g = palette_map[x.c2 * 4 + 1]; \
+        x.c2_r = palette_map[x.c2 * 4 + 0];
+
+struct
+{
+  unsigned short c1, c2;
+  unsigned char c1_r, c1_g, c1_b;
+  unsigned char c2_r, c2_g, c2_b;
+} quad[2][2];
+
+void AVI_Decode_Video1_16(
+  char *encoded,
+  int encoded_size,
+  char *decoded,
+  int width,
+  int height,
+  int bytes_per_pixel)
+{
+  int block_ptr, pixel_ptr;
+  int pixel_x, pixel_y;  // pixel width and height iterators
+  int block_x, block_y;  // block width and height iterators
+  int blocks_wide, blocks_high;  // width and height in 4x4 blocks
+  int block_inc;
+  int row_dec;
+
+  // decoding parameters
+  int stream_ptr;
+  unsigned char byte_a, byte_b;
+  unsigned short flags;
+  int skip_blocks;
+
+  stream_ptr = 0;
+  skip_blocks = 0;
+  blocks_wide = width / 4;
+  blocks_high = height / 4;
+  block_inc = 4 * bytes_per_pixel;
+  row_dec = (width + 4) * bytes_per_pixel;
+
+  for (block_y = blocks_high; block_y > 0; block_y--)
+  {
+    block_ptr = ((block_y * 4) - 1) * (width * bytes_per_pixel);
+    for (block_x = blocks_wide; block_x > 0; block_x--)
+    {
+      // check if this block should be skipped
+      if (skip_blocks)
+      {
+        block_ptr += block_inc;
+        skip_blocks--;
+        continue;
+      }
+
+      pixel_ptr = block_ptr;
+
+      // get the next two bytes in the encoded data stream
+      byte_a = encoded[stream_ptr++];
+      byte_b = encoded[stream_ptr++];
+
+      // check if the decode is finished
+      if ((byte_a == 0) && (byte_b == 0))
+        return;
+
+      // check if this is a skip code
+      else if ((byte_b & 0xFC) == 0x84)
+      {
+        // but don't count the current block
+        skip_blocks = ((byte_b - 0x84) << 8) + byte_a - 1;
+      }
+
+      // check if this is in the 2- or 8-color classes
+      else if (byte_b < 0x80)
+      {
+        flags = (byte_b << 8) | byte_a;
+
+        quad[0][0].c1 = LE_16(&encoded[stream_ptr]);
+        stream_ptr += 2;
+        quad[0][0].c2 = LE_16(&encoded[stream_ptr]);
+        stream_ptr += 2;
+
+        DECODE_BGR555_TO_BGR888(quad[0][0]);
+
+        if (quad[0][0].c1 & 0x8000)
+        {
+          // 8-color encoding
+          quad[1][0].c1 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+          quad[1][0].c2 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+          quad[0][1].c1 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+          quad[0][1].c2 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+          quad[1][1].c1 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+          quad[1][1].c2 = LE_16(&encoded[stream_ptr]);
+          stream_ptr += 2;
+
+          DECODE_BGR555_TO_BGR888(quad[0][1]);
+          DECODE_BGR555_TO_BGR888(quad[1][0]);
+          DECODE_BGR555_TO_BGR888(quad[1][1]);
+
+          for (pixel_y = 0; pixel_y < 4; pixel_y++)
+          {
+            for (pixel_x = 0; pixel_x < 4; pixel_x++)
+            {
+              if (flags & 1)
+              {
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_r;
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_g;
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_b;
+              }
+              else
+              {
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_r;
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_g;
+                decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_b;
+              }
+
+              // get the next flag ready to go
+              flags >>= 1;
+            }
+            pixel_ptr -= row_dec;
+          }
+        }
+        else
+        {
+          // 2-color encoding
+          for (pixel_y = 0; pixel_y < 4; pixel_y++)
+          {
+            for (pixel_x = 0; pixel_x < 4; pixel_x++)
+            {
+              if (flags & 1)
+              {
+                decoded[pixel_ptr++] = quad[0][0].c1_r;
+                decoded[pixel_ptr++] = quad[0][0].c1_g;
+                decoded[pixel_ptr++] = quad[0][0].c1_b;
+              }
+              else
+              {
+                decoded[pixel_ptr++] = quad[0][0].c2_r;
+                decoded[pixel_ptr++] = quad[0][0].c2_g;
+                decoded[pixel_ptr++] = quad[0][0].c2_b;
+              }
+
+              // get the next flag ready to go
+              flags >>= 1;
+            }
+            pixel_ptr -= row_dec;
+          }
+        }
+      }
+
+      // otherwise, it's a 1-color block
+      else
+      {
+        quad[0][0].c1 = (byte_b << 8) | byte_a;
+        DECODE_BGR555_TO_BGR888(quad[0][0]);
+
+        for (pixel_y = 0; pixel_y < 4; pixel_y++)
+        {
+          for (pixel_x = 0; pixel_x < 4; pixel_x++)
+          {
+            decoded[pixel_ptr++] = quad[0][0].c1_r;
+            decoded[pixel_ptr++] = quad[0][0].c1_g;
+            decoded[pixel_ptr++] = quad[0][0].c1_b;
+          }
+          pixel_ptr -= row_dec;
+        }
+      }
+
+      block_ptr += block_inc;
+    }
+  }
+}
+
+void AVI_Decode_Video1_8(
+  char *encoded,
+  int encoded_size,
+  char *decoded,
+  int width,
+  int height,
+  unsigned char *palette_map,
+  int bytes_per_pixel)
+{
+  int block_ptr, pixel_ptr;
+  int pixel_x, pixel_y;  // pixel width and height iterators
+  int block_x, block_y;  // block width and height iterators
+  int blocks_wide, blocks_high;  // width and height in 4x4 blocks
+  int block_inc;
+  int row_dec;
+
+  // decoding parameters
+  int stream_ptr;
+  unsigned char byte_a, byte_b;
+  unsigned short flags;
+  int skip_blocks;
+
+  stream_ptr = 0;
+  skip_blocks = 0;
+  blocks_wide = width / 4;
+  blocks_high = height / 4;
+  block_inc = 4 * bytes_per_pixel;
+  row_dec = (width + 4) * bytes_per_pixel;
+
+  for (block_y = blocks_high; block_y > 0; block_y--)
+  {
+    block_ptr = ((block_y * 4) - 1) * (width * bytes_per_pixel);
+    for (block_x = blocks_wide; block_x > 0; block_x--)
+    {
+      // check if this block should be skipped
+      if (skip_blocks)
+      {
+        block_ptr += block_inc;
+        skip_blocks--;
+        continue;
+      }
+
+      pixel_ptr = block_ptr;
+
+      // get the next two bytes in the encoded data stream
+      byte_a = encoded[stream_ptr++];
+      byte_b = encoded[stream_ptr++];
+
+      // check if the decode is finished
+      if ((byte_a == 0) && (byte_b == 0))
+        return;
+
+      // check if this is a skip code
+      else if ((byte_b & 0xFC) == 0x84)
+      {
+        // but don't count the current block
+        skip_blocks = ((byte_b - 0x84) << 8) + byte_a - 1;
+      }
+
+      // check if this is a 2-color block
+      else if (byte_b < 0x80)
+      {
+        flags = (byte_b << 8) | byte_a;
+
+        quad[0][0].c1 = (unsigned char)encoded[stream_ptr++];
+        quad[0][0].c2 = (unsigned char)encoded[stream_ptr++];
+
+        DECODE_PALETTE_TO_BGR888(quad[0][0]);
+
+        // 2-color encoding
+        for (pixel_y = 0; pixel_y < 4; pixel_y++)
+        {
+          for (pixel_x = 0; pixel_x < 4; pixel_x++)
+          {
+            if (flags & 1)
+            {
+              decoded[pixel_ptr++] = quad[0][0].c1_r;
+              decoded[pixel_ptr++] = quad[0][0].c1_g;
+              decoded[pixel_ptr++] = quad[0][0].c1_b;
+            }
+            else
+            {
+              decoded[pixel_ptr++] = quad[0][0].c2_r;
+              decoded[pixel_ptr++] = quad[0][0].c2_g;
+              decoded[pixel_ptr++] = quad[0][0].c2_b;
+            }
+
+            // get the next flag ready to go
+            flags >>= 1;
+          }
+          pixel_ptr -= row_dec;
+        }
+      }
+
+      // check if it's an 8-color block
+      else if (byte_b >= 0x90)
+      {
+        // 8-color encoding
+        quad[0][0].c1 = (unsigned char)encoded[stream_ptr++];
+        quad[0][0].c2 = (unsigned char)encoded[stream_ptr++];
+        quad[1][0].c1 = (unsigned char)encoded[stream_ptr++];
+        quad[1][0].c2 = (unsigned char)encoded[stream_ptr++];
+
+        quad[0][1].c1 = (unsigned char)encoded[stream_ptr++];
+        quad[0][1].c2 = (unsigned char)encoded[stream_ptr++];
+        quad[1][1].c1 = (unsigned char)encoded[stream_ptr++];
+        quad[1][1].c2 = (unsigned char)encoded[stream_ptr++];
+
+        DECODE_PALETTE_TO_BGR888(quad[0][0]);
+        DECODE_PALETTE_TO_BGR888(quad[0][1]);
+        DECODE_PALETTE_TO_BGR888(quad[1][0]);
+        DECODE_PALETTE_TO_BGR888(quad[1][1]);
+
+        for (pixel_y = 0; pixel_y < 4; pixel_y++)
+        {
+          for (pixel_x = 0; pixel_x < 4; pixel_x++)
+          {
+            if (flags & 1)
+            {
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_r;
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_g;
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c1_b;
+            }
+            else
+            {
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_r;
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_g;
+              decoded[pixel_ptr++] = quad[pixel_x >> 1][pixel_y >> 1].c2_b;
+            }
+
+            // get the next flag ready to go
+            flags >>= 1;
+          }
+          pixel_ptr -= row_dec;
+        }
+      }
+
+      // otherwise, it's a 1-color block
+      else
+      {
+        // init c2 along with c1 just so c2 is a known value for macro
+        quad[0][0].c1 = quad[0][0].c2 = byte_a;
+        DECODE_PALETTE_TO_BGR888(quad[0][0]);
+
+        for (pixel_y = 0; pixel_y < 4; pixel_y++)
+        {
+          for (pixel_x = 0; pixel_x < 4; pixel_x++)
+          {
+            decoded[pixel_ptr++] = quad[0][0].c1_r;
+            decoded[pixel_ptr++] = quad[0][0].c1_g;
+            decoded[pixel_ptr++] = quad[0][0].c1_b;
+          }
+          pixel_ptr -= row_dec;
+        }
+      }
+
+      block_ptr += block_inc;
+    }
+  }
+}
+
 


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