[flac-dev] Supporting real-time UTC timestamp data

Erik de Castro Lopo mle+la at mega-nerd.com
Sun Jun 15 03:25:11 PDT 2014

Declan Kelly wrote:

> Interesting article: "Time-coding audio files"
> http://www.windytan.com/2014/06/time-coding-audio-files.html
> The author is a signals hacker who has spoken at CCC and other events,
> and has determined that "There's no standard method for doing this with
> WAV or FLAC files".

There doesn't need to be. Both FLAC and WAV are limited to a single
sample rate for the whole recording. Therefore, all that is required
is a single indicating the UTC timestamp the recording was begun.

Broadcast WAV does indeed have a recording timestamp and there is

For FLAC the that timestamp can be trasnferred from the WAV file using
the  --keep-foreign-metadata option.

> The article proposes 2 methods (with working Perl code) to embed the
> time as in-band noise in the audio. One method (LSB stealing) requires
> lossless encoding; the other is audible but can survive lossy encoding.

Nice proof of concept, but i feel pretty useless in practice.

Erik de Castro Lopo

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