dvenc: do not call dsputil functions with stride not a multiple of 16

Allowing dsputil functions to assume the stride is a multiple of 16
even for smaller block sizes can simplify their implementation.
This appears to be the only place this guarantee is not met.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/dv.c

@@ -662,7 +662,7 @@ static int dv_encode_video_segment(AVCodecContext *avctx, void *arg)
     int mb_x, mb_y, c_offset, linesize, y_stride;
     uint8_t*  y_ptr;
     uint8_t*  dif;
-    LOCAL_ALIGNED_8(uint8_t, scratch, [64]);
+    LOCAL_ALIGNED_8(uint8_t, scratch, [128]);
     EncBlockInfo  enc_blks[5*DV_MAX_BPM];
     PutBitContext pbs[5*DV_MAX_BPM];
     PutBitContext* pb;
@@ -717,10 +717,10 @@ static int dv_encode_video_segment(AVCodecContext *avctx, void *arg)
                     b[0] = c_ptr[0]; b[1] = c_ptr[1]; b[2] = c_ptr[2]; b[3] = c_ptr[3];
                     b[4] =     d[0]; b[5] =     d[1]; b[6] =     d[2]; b[7] =     d[3];
                     c_ptr += linesize;
-                    b += 8;
+                    b += 16;
                 }
                 c_ptr = scratch;
-                linesize = 8;
+                linesize = 16;
             }
 
             vs_bit_size += dv_init_enc_block(    enc_blk++, c_ptr           , linesize, s, 1);