what's the usage and benefit of segments in Gnuraio `file meta sink`?

Question

In Gnuradio website, Max Seg. size is Length of a single segment before the header is repeated (in items)

At first,I think meta data will be changed along with the sample rate.I test several times,meta data just repeat the same content without any change when I use GUI range to change the sample rate.

Q1:What's the benefit for repeat same content times in meta sink file?

Second,I just need one meta header in one meta sink file. I tried int(32e24) but get OverflowError: in method 'file_meta_sink_make', argument 7 of type 'size_t'

Q2:how to set Max Seg. size to infinite?

Answer 1

The Gnu Radio Wiki says

The metadata consists of information such as a sample rate, absolute position in the stream sequence and data type. The stream tags can indicate any useful feature or information about the data stream. A new data segment is created when either:

1. A stream tag has been written (segments 1,2,3,5, and 6)
2. The data segment size maximum has been reached which is specified by the parameter "Max Seg. size" (segment 4). In this segment no stream tags are recorded.

So, there will be cases when segment metadata is "repeated" and other cases where it is not. It depends on what conditions caused the current segment to be closed and a new one created.

Remember that rx_rate as documented will be ignored if set by a tag. So check your example because sample rates absolutely are captured in the segment metadata. (If not and you think you have a defect case, then it would be best to come up with a small, reproducible example and submit that to wherever Gnu Radio wants bug reports sent to.)

I would assume that, since it looks like Max Seg. size is an unsigned 32-bit integer, this is is the maximum item size you can set.