static int ipvideo_decode_block_opcode_0x2(IpvideoContext *s) { unsigned char B; int x, y; /* copy block from 2 frames ago using a motion vector; need 1 more byte */ CHECK_STREAM_PTR(s->stream_ptr, s->stream_end, 1); B = *s->stream_ptr++; if (B < 56) { x = 8 + (B % 7); y = B / 7; } else { x = -14 + ((B - 56) % 29); y = 8 + ((B - 56) / 29); } debug_interplay (" motion byte = %d, (x, y) = (%d, %d)\n", B, x, y); return copy_from(s, &s->second_last_frame, x, y); }