Dear Sir,
These features could be implemented but are not available in the reference firmware. You are indeed correct, the application uploads data to a waveform memory and the samples are then played back.
FMC204 shall be modified to not have a waveform memory and push data received from the data bus directly to the DAC. Investigation on the data bus bandwidth is required to know if you have enough bandwidth or not.
The steps to reach these goals are unfortunately not covered by technical support so this will need to be implemented by you.
On the software side, the API is offloading data so in theory you could stream data. The problem is more about the bandwidth available on the Ethernet link, only a couple of MB/s which is not going to be enough to stream the DAC device.
Best Regards,
Arnaud