String containing custom AAC+ options to send to the FdkAac encoder.
For advanced users, this string allows applying all of the possible AAC+ encoding options available with FdkAac. See Appendix F - FdkAac command line for the complete set of available options.
This property is used only if the EncodeFormats.FormatToUse property is set to ENCODING_FORMAT_AAC_PLUS and the EncodeFormats.AACPlus.EncodeMode property is set to AACPLUS_ENCODE_CUSTOM.
IMPORTANT NOTE: As you may know, the Fdkaac command line is as follows:
usage: fdkaac [options] input_file
Contents of the CustomString property are related to the [options] field only so you must omit entering the word fdkaac and omit to specify the input_file and -o <filename> settings also. You should also omit the -S and --raw options which are already applied internally.
For further details about encoding in AAC+ format refer to the EncodeAACPlus class section.
For further information about available encoding formats see the EncodeFormatsMan class.