further work on the RoQ audio decoder

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@4487 b3059339-0415-0410-9bf9-f77b7e298cf2

1 files changed, 56 insertions, 1 deletions

diff --git a/roqav.c b/roqav.c
index f1bcd51b98..40eac00673 100644
--- a/roqav.c
+++ b/roqav.c
@@ -1,17 +1,24 @@
 /*
         RoQ A/V decoder for the MPlayer program
         by Mike Melanson
-        based on Dr. Tim Ferguson's RoQ document found at:
+        based on Dr. Tim Ferguson's RoQ document and accompanying source
+        code found at:
           http://www.csse.monash.edu.au/~timf/videocodec.html
 */
 
 #include "config.h"
 #include "bswap.h"
 #include <stdio.h>
+#include <stdlib.h>
 
 #define LE_16(x) (le2me_16(*(unsigned short *)(x)))
 #define LE_32(x) (le2me_32(*(unsigned int *)(x)))
 
+#define CLAMP_S16(x)  if (x < -32768) x = -32768; \
+  else if (x > 32767) x = 32767;
+#define SE_16BIT(x)  if (x & 0x8000) x -= 0x10000;
+// sign extend a 4-bit value
+
 void *roq_decode_video_init(void)
 {
 }
@@ -26,14 +33,62 @@ void roq_decode_video(
 {
 }
 
+// Initialize the RoQ audio decoder, which is to say, initialize the table
+// of squares.
 void *roq_decode_audio_init(void)
 {
+  short *square_array;
+  short square;
+  int i;
+
+  square_array = (short *)malloc(256 * sizeof(short));
+  if (!square_array)
+    return NULL;
+
+  for (i = 0; i < 128; i++)
+  {
+    square = i * i;
+    square_array[i] = square;
+    square_array[i + 128] = -square;
+  }
+
+  return square_array;
 }
 
 int roq_decode_audio(
   unsigned short *output,
   unsigned char *input,
+  int encoded_size,
   int channels,
   void *context)
 {
+  short *square_array = (short *)context;
+  int i;
+  int predictor[2];
+  int channel_number = 0;
+
+  // prepare the initial predictors
+  if (channels == 1)
+    predictor[0] = LE_16(&input[0]);
+  else
+  {
+    predictor[0] = input[1] << 8;
+    predictor[1] = input[0] << 8;
+  }
+  SE_16BIT(predictor[0]);
+  SE_16BIT(predictor[1]);
+
+  // decode the samples
+  for (i = 2; i < encoded_size; i++)
+  {
+    predictor[channel_number] += square_array[input[i]];
+    CLAMP_S16(predictor[channel_number]);
+    output[i - 2] = predictor[channel_number];
+
+    // toggle channel
+    channel_number ^= channels - 1;
+  }
+
+  // return the number of samples decoded
+  return (encoded_size - 2);
 }