avfilter/vf_stereo3d: fix interleaved columns output

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_stereo3d.c

@@ -899,37 +899,37 @@ copy:
 
                 switch (s->pixstep[i]) {
                 case 1:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=2, p++, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=2, p++, b+=2) {
                         dst[x  ] =   b&1  ? left[p] : right[p];
                         dst[x+1] = !(b&1) ? left[p] : right[p];
                     }
                     break;
                 case 2:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=4, p+=2, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=4, p+=2, b+=2) {
                         AV_WN16(&dst[x  ],   b&1  ? AV_RN16(&left[p]) : AV_RN16(&right[p]));
                         AV_WN16(&dst[x+2], !(b&1) ? AV_RN16(&left[p]) : AV_RN16(&right[p]));
                     }
                     break;
                 case 3:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=6, p+=3, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=6, p+=3, b+=2) {
                         AV_WB24(&dst[x  ],   b&1  ? AV_RB24(&left[p]) : AV_RB24(&right[p]));
                         AV_WB24(&dst[x+3], !(b&1) ? AV_RB24(&left[p]) : AV_RB24(&right[p]));
                     }
                     break;
                 case 4:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=8, p+=4, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=8, p+=4, b+=2) {
                         AV_WN32(&dst[x  ],   b&1  ? AV_RN32(&left[p]) : AV_RN32(&right[p]));
                         AV_WN32(&dst[x+4], !(b&1) ? AV_RN32(&left[p]) : AV_RN32(&right[p]));
                     }
                     break;
                 case 6:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=12, p+=6, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=12, p+=6, b+=2) {
                         AV_WB48(&dst[x  ],   b&1  ? AV_RB48(&left[p]) : AV_RB48(&right[p]));
                         AV_WB48(&dst[x+6], !(b&1) ? AV_RB48(&left[p]) : AV_RB48(&right[p]));
                     }
                     break;
                 case 8:
-                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=16, p+=8, b++) {
+                    for (x = 0, b = 0, p = 0; x < s->linesize[i] * 2; x+=16, p+=8, b+=2) {
                         AV_WN64(&dst[x  ],   b&1 ?  AV_RN64(&left[p]) : AV_RN64(&right[p]));
                         AV_WN64(&dst[x+8], !(b&1) ? AV_RN64(&left[p]) : AV_RN64(&right[p]));
                     }