That corresponds to a sustained data rate of 10,080 bits per second. With the error correction disabled you can add another 10 bytes per field for a rate of 14,880 bits. And in addition, you can still insert up to 30 rows of 64 alphanumeric characters. But if 31 bytes per field isn't enough, we have the model 6020. And where the picture is not occupied with data, you can insert up to 30 rows of 32 alphanumeric characters.
Full update can occur each field.
All features can be enabled or disabled under program control. The video bandpass is absolutely flat to beyond 20MHz. By the way, if you would like to decode the data produced by the 9938 or 6020, why not take a look at one of the ITS Video Readers such as the VMEbus model 6073 or the stand-alone model 6042. They can decode, reinsert, produce computer compatible messages and digitize points of interest in the video scene. NTSC Synchronizer may solve your problem.