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Interpolate depth for samples that have no depth

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When downloading from libdivecomputer, we used to initialize the depth
of a sample to the previous depth.  However, at least for the Suunto EON
Steel, you can get sample times without any actual depth reading - the
time might be associated with some ranbdom event rather than a new depth
sample.

Rather than initialize these samples to have the same depth as the
previous one (and then perhaps getting a very sudden jump when the
*real* depth event comes in a second later), initialize the depth
samples to -1, and if that sample doesn't get a real depth, we'll create
an interpolated depth.

It is possible that we should just carry the sample around as not
actually having a depth, and instead just interpolate in the plot_info
generation, but at least right now we have a ton of code that "knows"
that every sample has a depth.  Not the least of which is our own save
format.

So generating an interpolated depth seems the path of least resistance,
and at least makes the graph look correct - no odd staircase effect from
other events that happen in between depth samples.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Linus Torvalds 2015-10-25 12:02:08 +09:00 • committed by Dirk Hohndel
parent cd1884b29c
commit 2b1017c986
2 changed files with 29 additions and 4 deletions
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22
dive.c
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@ -1243,6 +1243,23 @@ static void fixup_dc_events(struct divecomputer *dc)
}
}
static int interpolate_depth(struct divecomputer *dc, int idx, int lastdepth, int lasttime, int now)
{
int i;
int nextdepth = lastdepth;
int nexttime = now;
for (i = idx+1; i < dc->samples; i++) {
struct sample *sample = dc->sample + i;
if (sample->depth.mm < 0)
continue;
nextdepth = sample->depth.mm;
nexttime = sample->time.seconds;
break;
}
return interpolate(lastdepth, nextdepth, now-lasttime, nexttime-lasttime);
}
static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
{
int i, j;
@ -1276,6 +1293,11 @@ static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
int o2_pressure = sample->o2cylinderpressure.mbar;
int index;
if (depth < 0) {
depth = interpolate_depth(dc, i, lastdepth, lasttime, time);
sample->depth.mm = depth;
}
/* if we have an explicit first cylinder */
if (sample->sensor == 0 && first_cylinder != 0)
sample->sensor = first_cylinder;