writing MXF video the includes GPS times

Cory Albright cory.albright at sri.com
Thu Aug 11 09:16:12 PDT 2011

Unfortunately I do not have a specification for exactly how the GPS time is embedded, but I do have a sample video that was constructed by different means that does contain the GPS times.  Maybe a little reverse engineering will help with this.  I am new to gstreamer (and MXF), so I still have some learning to do.
     It is my understanding that the time is to be saved in the header of each frame, as opposed to a timestamp at the start and calculating relative offsets based on frame number.

- Cory

2011/8/11 Sebastian Dr?ge<sebastian.droege at collabora.co.uk>

> On Wed, 2011-08-10 at 17:30 -0600, Cory Albright wrote:
>> I am needing to export rendered frames from my application to an MXF
>> video file.  The application is rendering based on a GPS time-clock and
>> I need to have the GPS time embedded into the frame headers of the MXF
>> video.   Does the MXF plugin for gstreamer support this?
> Hi,
> currently the MXF plugin does not support this but it should be possible
> to add support for this. Based on which specification do you want to add
> the GPS time into the frame headers?
I would be interested in this as well, as I'll likely have a need to support
this in the future. Do you want to save the GPS (UTC) date and time along
with every frame (perhaps interpolated), just at the start (using relative
offsets for each frame), or at the sampling rate of the GPS (typ. 1-10Hz)?

Taking a quick look at the SMPTE metadata dictionary shows a lot of
time-related keys, but I haven't worked with this before so I'm not sure
which ones are appropriate. The SMPTE item for temporal keys is My complete guess without reading any of the
standards or RPs would be that you'd want to use:
Material Start True Date-Time, UTC, ("Absolute time at start of creating the
segment, shot, clip, item etc."). Again, a complete guess, I'm not sure
what's recommended or actually supported by software implementations.


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