When channel of nullSrc is configured as SYSTEM_SF_PROGRESSIVE, the corresponding Dei setting, enableDeiForceBypass, is TRUE, so I think we don't configure enableDeiForceBypass TRUE for interlaced video.
If two channels are progressive, the fps is correct. However, if the second channel is configured as interlaced, the fps of first channel is only 16...
Note.
Select link always selects channel 0 to Dei0 and channel 1 to Dei1.
ch0:
nullSrc [SYSTEM_SF_PROGRESSIVE]
Dei0 [enableDeiForceBypass = TRUE]
FPS = 16
ch1:
nullSrc [SYSTEM_SF_INTERLACED]
Dei1 [enableDeiForceBypass = FALSE]
FPS = 30