CaptionSourceByteRateLimit
Choose whether to limit the byte rate at which your SCC input captions are inserted into your output. To not limit the caption rate: We recommend that you keep the default value, Disabled. MediaConvert inserts captions in your output according to the byte rates listed in the EIA-608 specification, typically 2 or 3 caption bytes per frame depending on your output frame rate. To limit your output caption rate: Choose Enabled. Choose this option if your downstream systems require a maximum of 2 caption bytes per frame. Note that this setting has no effect when your output frame rate is 30 or 60.