Currently, the following fails:

db.c.aggregate([{$project: {_id: 1, output: {$convert: {to: {type: "binData", subtype: 9}, input: [NumberInt(200)], format: "base64"}}}}]); 

Because 200 is outside the range of an INT8.

We can support this by creating a new BinData vector type that allows for int types larger than INT8, or by implicitly converting to float32 (with possible loss of precision).