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Interval sampling stamped each frame with the start time of the video plus its time in the video. A timelapse packs several seconds of capture into each second of video, so its frames were stamped that many times too close together. Geotagged from a GPX by those stamps, they all landed near the start of the track. Geotagged from the video's own track, they moved so far per second that the speed check could reject them: a 30x timelapse of a drive read as over 1,000 km/h. Interval sampling now reads the rate from the video's GPS clock, as GPX sync does, and stamps the frames at it. The start time is mapped back from the first GPS timestamps at the same rate. --video_duration_ratio, which used to apply to every video, now paces only the videos without a GPS clock, so that a ratio given for those leaves the other videos in the batch alone. The samples are then geotagged from the video's own track (the gopro, camm and blackvue sources) by their time since the first sample, while the track is timed in video seconds. It is now timed in GPS seconds, at the rate of its clock. That also fixes distance samples of a timelapse, which were already stamped with their capture times.
--interpolation_use_gpx_start_time places the GPX from the start of the video instead of by the video's GPS clock. It skipped reading the clock altogether, and with it the clock's rate, so a timelapse got its GPX laid out at 1x: a 5 s, 30x timelapse got 157 s of GPX, and distance sampling picked 5 frames along its first 12 m instead of 148 along the 1.4 km route. The clock is now read in that mode too, and placed at the start of the GPX, so that only its rate is used. A video that is not a timelapse has a rate of 1, and is placed as before. The coverage check raises when the clock a track was placed by says that the track misses the video. A clock placed at the start of the GPX says nothing of the kind, so a track placed in that mode still only warns, as it did when it had no clock.
A timelapse packs several seconds of capture into each second of video. With a GPS clock of its own, a GPX is synced at the clock's rate. Without one, nothing in the video tells the rate, and the GPX was laid out at 1x, so the frames got only the start of the track: an Insta360 ONE X timelapse, 1.8 s of video with a 110 s GPX, gave 1 frame. --video_duration_ratio, the seconds of real time per second of video, used to apply to interval sampling only, and was marked deprecated. It now paces the GPX of a video without a GPS clock in distance sampling too, whether the GPX is placed by --video_start_time, by --interpolation_use_gpx_start_time or by assuming that it starts with the video. The GPS clock of a video, if it has one, still wins. The ratio is required where a track runs on long after the video and nothing else accounts for it. Without a start time, a track more than twice as long as the video was already refused; it is now measured against the time the video spans at the ratio, and the error names the ratio. With --interpolation_use_gpx_start_time, such a track is now refused as well, in interval sampling too, as it belongs to a timelapse or to more than this video. With --video_start_time nothing is required, so that one GPX can serve many videos, each placed by its start time. process is unchanged.
It said that a GPX works with interval sampling only, which has not been true since distance sampling honours --geotag_source, and that the start time of a video is always read from its GPS or its creation time, which distance sampling does not do. It now says how each kind of video is placed along a GPX, how --video_start_time lets one GPX serve several videos, and how --video_duration_ratio paces a timelapse without a GPS clock. The --interpolation_use_gpx_start_time example drops the interval sampling options it no longer needs.
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Stacked on #856; only the last commit is new.
The README said that a GPX works with interval sampling only, which hasn't been true since #841, and that a video's start time is always read from its GPS or creation time, which distance sampling doesn't do. It now says how each kind of video is placed along a GPX, how
--video_start_timelets one GPX serve several videos, and how--video_duration_ratiopaces a timelapse without a GPS clock. The--interpolation_use_gpx_start_timeexample drops the interval sampling options it no longer needs.It doesn't touch "Limitations of
--video_geotag_source", which #851 rewrites.