- time_unit_ = util::Samples;
-
- shared_lock<shared_mutex> lock(session().signals_mutex());
- const unordered_set< shared_ptr<Signal> > &sigs(session().signals());
-
- // Check all signals but...
- for (const shared_ptr<Signal> signal : sigs) {
- const shared_ptr<SignalData> data = signal->data();
-
- // ...only check first segment of each
- const vector< shared_ptr<Segment> > segments = data->segments();
- if (!segments.empty())
- if (segments[0]->samplerate()) {
- time_unit_ = util::Time;
- break;
- }
+ // Check whether we know the sample rate and hence can use time as the unit
+ if (time_unit_ == util::Samples) {
+ shared_lock<shared_mutex> lock(session().signals_mutex());
+ const unordered_set< shared_ptr<Signal> > &sigs(session().signals());
+
+ // Check all signals but...
+ for (const shared_ptr<Signal> signal : sigs) {
+ const shared_ptr<SignalData> data = signal->data();
+
+ // ...only check first segment of each
+ const vector< shared_ptr<Segment> > segments = data->segments();
+ if (!segments.empty())
+ if (segments[0]->samplerate()) {
+ time_unit_ = util::Time;
+ break;
+ }
+ }