Channel padding logic should be enabled when AXI4-Stream master interfacing with UHD-SDI Audio (Embed) is a non-multiple of four source. (Example 5.1 system generates 6 samples which is non-multiple of four. Similarly AES3/SPDIF generates two samples which is non multiple of four.)
Embedding of audio in SDI is performed on group granularity (each group consist of four channels of audio). When enabled, Channel padding logic converts the non-multiple of four channel AXI4-S transactions (2, 6, 10, 14, etc.) to multiple of four channel transactions (4, 8, 12, 16, etc.) by padding the remaining two channels with mute data.