ff_copy_bits() optimization

Originally committed as revision 2777 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.c

@@ -3732,21 +3732,26 @@ void ff_mpeg_flush(AVCodecContext *avctx){
 #ifdef CONFIG_ENCODERS
 void ff_copy_bits(PutBitContext *pb, uint8_t *src, int length)
 {
+    const uint16_t *srcw= src;
     int words= length>>4;
     int bits= length&15;
     int i;
 
     if(length==0) return;
     
-    if(put_bits_count(pb)&7){
-        for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(((uint16_t*)src)[i]));
+    if(words < 16){
+        for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
+    }else if(put_bits_count(pb)&7){
+        for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
     }else{
+        for(i=0; put_bits_count(pb)&31; i++)
+            put_bits(pb, 8, src[i]);
         flush_put_bits(pb);
-        memcpy(pbBufPtr(pb), src, 2*words);
-        skip_put_bytes(pb, 2*words);
+        memcpy(pbBufPtr(pb), src+i, 2*words-i);
+        skip_put_bytes(pb, 2*words-i);
     }
         
-    put_bits(pb, bits, be2me_16(((uint16_t*)src)[words])>>(16-bits));
+    put_bits(pb, bits, be2me_16(srcw[words])>>(16-bits));
 }
 
 static inline void copy_context_before_encode(MpegEncContext *d, MpegEncContext *s, int type){