[Discuss-gnuradio] tag propagation in GNU Radio blocks

[Nowlan, Sean]

How does tag propagation work in these 3 cases? Up until now I’ve only been dealing with tags on streams running at the output rate of a USRP sink. I’ve stated the assumed answers, but haven’t tested…

1) gr_sync_block (interpolation by factor L): tag on incoming sample x will be moved to sample x*L in output stream

 

2) gr_sync_block (decimation by factor M): tag on incoming sample x will be moved to sample FLOOR(x/M) in output stream

 

3) gr_block with arbitrary relationship: user has to move tags him/herself in general_work.

 

Another question: does the scheduler re-number absolute sample offsets after every rate-changing block, or does it work backwards from a sink block all the way to the source block so that absolute offsets are relative to the output? I can see this getting more hairy when multiple source and sink blocks are used.

 

Thanks,

Sean