AS-11 is a standard for delivering broadcast video for playback. It is comprised of AVC-Intra video and PCM audio and is wrapped in a vendor-neutral MXF file.
In order to create an AS-11 output, set the format_preset parameter to "as11_hd". Currently, audio is limited to 2-channel PCM Audio, with a max sample rate of 48Khz. For more information on AVC-Intra outputs, check out the documentation here.