break;
case MODE_INTERLACEX2: /* re-interlace preserving image height, double frame rate */
/* output current frame first */
- out = avfilter_ref_buffer(cur, AV_PERM_READ);
+ out = avfilter_ref_buffer(cur, ~AV_PERM_WRITE);
out->video->interlaced = 1;
ff_start_frame(outlink, out);