[Bug 774050] New: audiotestsrc: Improvements to the "ticks" waveform

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=774050

            Bug ID: 774050
           Summary: audiotestsrc: Improvements to the "ticks" waveform
    Classification: Platform
           Product: GStreamer
           Version: git master
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-base
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: dv at pseudoterminal.org
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

The ticks waveform can be useful for audio synchronization diagnostics and
other cases where the time offset between waveforms is important. However, in
its current form, it is too limited, and has problems with discontinuities,
which result in severe artifacts when this waveform is output by a DAC.

These patches fix some discontinuities and considerably expand the ticks
waveform's flexibility.

They also introduce the notion of a "marker tick"; every Nth tick can have a
different amplitude (usually one that is larger than the others). This is
useful for combining frequent oscilloscope triggering with large time offset
detection. For example, without marker ticks, the tick intervals must not be
too small, otherwise the maximum time offset that can be unambiguously detected
is quite small (for example, if the interval is 50ms, then no time offset
larger than 25ms can be unambiguously recognized). If the tick intervals are
too far apart, then no sudden changes can be clearly observed, since the
oscilloscope is not updated quickly enough. But with marker ticks, this is not
an issue: If there's for example a tick every 100 ms, then the oscilloscope can
be triggered every 100 ms. And, if every 20th tick is a marker tick, then time
offsets of up to 1 second can be discovered, even though the time between ticks
is 100 ms.

The patches also apply some minor cleanup to the audiotestsrc documentation.

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