mlpdec: Don't overallocate buffers.

Now that max channels and primitive matrices are properly validated, there is
no need to be paranoid that random data will be overwritten.
As a bonus this makes matrix_coeff 16-byte aligned between matrices.

Originally committed as revision 18651 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mlp.h

@@ -29,15 +29,18 @@
 /** Last possible matrix channel for each codec */
 #define MAX_MATRIX_CHANNEL_MLP      5
 #define MAX_MATRIX_CHANNEL_TRUEHD   7
-/** Maximum number of channels that can be decoded. */
-#define MAX_CHANNELS        16
+/** Maximum number of channels in a valid stream.
+ *  MLP   : 5.1 + 2 noise channels -> 8 channels
+ *  TrueHD: 7.1                    -> 8 channels
+ */
+#define MAX_CHANNELS                8
 
 /** Maximum number of matrices used in decoding; most streams have one matrix
  *  per output channel, but some rematrix a channel (usually 0) more than once.
  */
 #define MAX_MATRICES_MLP            6
 #define MAX_MATRICES_TRUEHD         8
-#define MAX_MATRICES        15
+#define MAX_MATRICES                8
 
 /** Maximum number of substreams that can be decoded.
  *  MLP's limit is 2. TrueHD supports at least up to 3.

libavcodec/mlpdec.c

@@ -93,7 +93,7 @@ typedef struct SubStream {
     //! Whether the LSBs of the matrix output are encoded in the bitstream.
     uint8_t     lsb_bypass[MAX_MATRICES];
     //! Matrix coefficients, stored as 2.14 fixed point.
-    int32_t     matrix_coeff[MAX_MATRICES][MAX_CHANNELS+2];
+    int32_t     matrix_coeff[MAX_MATRICES][MAX_CHANNELS];
     //! Left shift to apply to noise values in 0x31eb substreams.
     uint8_t     matrix_noise_shift[MAX_MATRICES];
     //@}
@@ -143,7 +143,7 @@ typedef struct MLPDecodeContext {
 
     int8_t      noise_buffer[MAX_BLOCKSIZE_POW2];
     int8_t      bypassed_lsbs[MAX_BLOCKSIZE][MAX_CHANNELS];
-    int32_t     sample_buffer[MAX_BLOCKSIZE][MAX_CHANNELS+2];
+    int32_t     sample_buffer[MAX_BLOCKSIZE][MAX_CHANNELS];
 } MLPDecodeContext;
 
 static VLC huff_vlc[3];