simplifying the code as per Michael's suggestion

Originally committed as revision 15577 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/dv.c

@@ -492,7 +492,7 @@ static inline void dv_decode_video_segment(DVVideoContext *s,
         mb_x = v & 0xff;
         mb_y = v >> 8;
         /* We work with 720p frames split in half. The odd half-frame (chan==2,3) is displaced :-( */
-        if (s->sys->height == 720 && ((s->buf[1]>>2)&0x3) == 0) {
+        if (s->sys->height == 720 && !(s->buf[1]&0x0C)) {
                mb_y -= (mb_y>17)?18:-72; /* shifting the Y coordinate down by 72/2 macroblocks */
         }
 

libavformat/dv.c

@@ -122,7 +122,7 @@ static int dv_extract_audio(uint8_t* frame, uint8_t* ppcm[4],
     half_ch = sys->difseg_size/2;
 
     /* We work with 720p frames split in half, thus even frames have channels 0,1 and odd 2,3 */
-    ipcm = (sys->height == 720 && ((frame[1]>>2)&0x3) == 0)?2:0;
+    ipcm = (sys->height == 720 && !(frame[1]&0x0C))?2:0;
     pcm = ppcm[ipcm++];
 
     /* for each DIF channel */
@@ -339,7 +339,7 @@ int dv_produce_packet(DVDemuxContext *c, AVPacket *pkt,
 
     /* We work with 720p frames split in half, thus even frames have channels 0,1 and odd 2,3 */
     if (c->sys->height == 720) {
-        if (((buf[1]>>2)&0x3))
+        if (buf[1]&0x0C)
             c->audio_pkt[2].size = c->audio_pkt[3].size = 0;
         else
             c->audio_pkt[0].size = c->audio_pkt[1].size = 0;