Timestamp in saved data

There was discussion once about file formats for saved data.

I just used Jim Cooley’s file headers to put timestamps in my
shortwave radio data so when I play back a pirate radio broadcast
I can see that, hey, that was on last Saturday at 8:15PM. The
gui now sports a clock showing either current or playback time.

gr.file_hdr_sink|source seem pretty flexible, just an arbitrary
length of int’s that can mean anything you want to define. Anyway,
if they were made an integral part or gnuradio I will update the
gnuradio-examples/python/apps/hf_explorer to include the new feature.

–Chuck

On Tue, 2006-09-19 at 11:45 -0400, Charles S. wrote:

I just used Jim Cooley’s file headers to put timestamps in my
shortwave radio data so when I play back a pirate radio broadcast
I can see that, hey, that was on last Saturday at 8:15PM. The
gui now sports a clock showing either current or playback time.

gr.file_hdr_sink|source seem pretty flexible, just an arbitrary
length of int’s that can mean anything you want to define. Anyway,

Oh well - unfortunately, it’s a case of gaining on thing, metadata, but
losing another, the ability to SEEK around in the data file!

–Chuck

On Tue, Sep 19, 2006 at 06:04:15PM -0400, Chuck Swiger wrote:

Oh well - unfortunately, it’s a case of gaining on thing, metadata, but
losing another, the ability to SEEK around in the data file!

Actually, best I can do with header timestamps is a ‘fast forward’ by
connecting the file src to a null_sink, that does about a minute every 3
seconds :wink: Rewind is still impossible, but de-headering to raw data
is easy.

–Chuck

Chuck,

gr.file_source has a seek method which will allow you to seek
instantly anywhere in the file.

[Actually, I note that it’s defined with a long instead of int64_t
offset, so to move more than 4GB, you have to do it in multiple steps]

Eric

On Tue, 2006-09-19 at 13:28 -0400, Charles S. wrote:

losing another, the ability to SEEK around in the data file!

Actually, best I can do with header timestamps is a ‘fast forward’ by
connecting the file src to a null_sink, that does about a minute every 3
seconds :wink: Rewind is still impossible, but de-headering to raw data
is easy.

–Chuck

On Tue, 2006-09-19 at 15:06 -0700, Eric B. wrote:

gr.file_source has a seek method which will allow you to seek
instantly anywhere in the file.

Yep - I use that all the time. The extra challenge was to put
time-stamping information in a data file using Cooley’s file
headers

http://alumni.media.mit.edu/~jcooley/gr_experiments/experiments/gr_header.htm

that uses a header-size and data-size that can’t just
be skipped over w/o everything getting out of sync.

Anyway, mission (mostly) accomplished - and being able to embed
information like decimation, center frequency, time of day, gps
position, etc is pretty handy.

–Chuck

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