File Meta Sink

Write stream to file with meta-data headers.

These files represent data as binary information in between meta-data headers. The headers contain information about the type of data and properties of the data in the next segment of samples. The information includes:

• rx_rate (double): sample rate of data.
• rx_time (uint64_t, double): time stamp of first sample in segment.
• size (uint32_t): item size in bytes.
• type (::gr_file_types as int32_t): data type.
• cplx (bool): Is data complex?
• strt (uint64_t): Starting byte of data in this segment.
• bytes (uint64_t): Size in bytes of data in this segment.

Tags can be sent to the file to update the information, which will create a new header. Headers are found by searching from the first header (at position 0 in the file) and reading where the data segment starts plus the data segment size. Following will either be a new header or EOF.

Use of the pmt package to specify parameter Extra Dict requires an Import block with import pmt.

Parameters

(R): Run-time adjustable

File (R)

Name of file to write data to.

Sample Rate

Sample rate of data. If sample rate will be set by a tag, such as rx_tag from a UHD source, this is basically ignored.

Relative_rate

Rate chance from source of sample rate tag to sink.

Max Seg. size

Length of a single segment before the header is repeated (in items).

Extra dict.

A PMT dictionary of extra information. This field is required, and pre-filled as pmt.make_dict().

Detached header

Set to true to store the header info in a separate file (named filename.hdr)

Unbuffered (R)

If new samples are flushed to file at the end of each call to the work function

Example Flowgraph

In this example, the file meta sink block is saving both a data stream from the signal source generating a saw tooth waveform and stream tags that align with the start for the saw tooth waveform.

Source Files

C++ files

[1]

[2]

Header files

[3]

Public header files

[4]

Block definition

[5]