[time-nuts] Audio format with embedded timestamps?

Chris Caudle chris at chriscaudle.org
Fri Dec 2 12:20:26 EST 2016


On Thu, December 1, 2016 8:19 am, Tim Shoppa wrote:
> Is there a common digital audio format that embeds in the digital
> stream, a timestamp marker of real-world-clock-time that the
> audio was recorded at?
>
> At my "day job" we have many digital "system of record" phone and radio
> recording systems. The best they do, is to timestamp the filenames they
> generate with the start time.

You mention timestamping files, and also digital stream.  Are you looking
for a transport protocol, or a file format?

For a file format, Broadcast WAV described in EBU tech report 3285 has a
field for origination time, with a resolution of 1 second, and a time
reference which as I understand is the location of the first sample
referred to the previous midnight given in sample position as a 64 bit
number.
Presumably this give some ambiguity of the location of the ending samples
based on the accuracy of the sample clock originally used to capture the
samples.

If you need transport time stamps, then the audio-over-IP protocols use
PTP as the reference clock, so you get explicit description of the audio
sample location referenced to the PTP epoch.

-- 
Chris Caudle




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