Index: webrtc/base/timestampaligner.cc |
diff --git a/webrtc/base/timestampaligner.cc b/webrtc/base/timestampaligner.cc |
index 41cac9bde0f436125a764813728c702062add599..281da8f862c115273153c2b673de312b63166270 100644 |
--- a/webrtc/base/timestampaligner.cc |
+++ b/webrtc/base/timestampaligner.cc |
@@ -8,15 +8,30 @@ |
* be found in the AUTHORS file in the root of the source tree. |
*/ |
+#include <limits> |
+ |
+#include "webrtc/base/checks.h" |
#include "webrtc/base/logging.h" |
#include "webrtc/base/timestampaligner.h" |
+#include "webrtc/base/timeutils.h" |
namespace rtc { |
-TimestampAligner::TimestampAligner() : frames_seen_(0), offset_us_(0) {} |
+TimestampAligner::TimestampAligner() |
+ : frames_seen_(0), |
+ offset_us_(0), |
+ clip_bias_us_(0), |
+ prev_translated_time_us_(std::numeric_limits<int64_t>::min()) {} |
TimestampAligner::~TimestampAligner() {} |
+int64_t TimestampAligner::TranslateTimestamp(int64_t camera_time_us, |
+ int64_t system_time_us) { |
+ return ClipTimestamp( |
+ camera_time_us + UpdateOffset(camera_time_us, system_time_us), |
+ system_time_us); |
+} |
+ |
int64_t TimestampAligner::UpdateOffset(int64_t camera_time_us, |
int64_t system_time_us) { |
// Estimate the offset between system monotonic time and the capture |
@@ -63,18 +78,19 @@ int64_t TimestampAligner::UpdateOffset(int64_t camera_time_us, |
// If the current difference is far from the currently estimated |
// offset, the filter is reset. This could happen, e.g., if the |
// camera clock is reset, or cameras are plugged in and out, or if |
- // the application process is temporarily suspended. The limit of |
- // 300 ms should make this unlikely in normal operation, and at the |
- // same time, converging gradually rather than resetting the filter |
- // should be tolerable for jumps in camera time below this |
- // threshold. |
- static const int64_t kResetLimitUs = 300000; |
- if (std::abs(error_us) > kResetLimitUs) { |
+ // the application process is temporarily suspended. Expected to |
+ // happen for the very first timestamp (|frames_seen_| = 0). The |
+ // threshold of 300 ms should make this unlikely in normal |
+ // operation, and at the same time, converging gradually rather than |
+ // resetting the filter should be tolerable for jumps in camera time |
+ // below this threshold. |
+ static const int64_t kResetThresholdUs = 300000; |
+ if (std::abs(error_us) > kResetThresholdUs) { |
LOG(LS_INFO) << "Resetting timestamp translation after averaging " |
<< frames_seen_ << " frames. Old offset: " << offset_us_ |
<< ", new offset: " << diff_us; |
frames_seen_ = 0; |
- prev_translated_time_us_ = rtc::Optional<int64_t>(); |
+ clip_bias_us_ = 0; |
} |
static const int kWindowSize = 100; |
@@ -85,23 +101,34 @@ int64_t TimestampAligner::UpdateOffset(int64_t camera_time_us, |
return offset_us_; |
} |
-int64_t TimestampAligner::ClipTimestamp(int64_t time_us, |
+int64_t TimestampAligner::ClipTimestamp(int64_t filtered_time_us, |
int64_t system_time_us) { |
- // Make timestamps monotonic. |
- if (!prev_translated_time_us_) { |
- // Initialize. |
- clip_bias_us_ = 0; |
- } else if (time_us < *prev_translated_time_us_) { |
- time_us = *prev_translated_time_us_; |
- } |
- |
- // Clip to make sure we don't produce time stamps in the future. |
- time_us -= clip_bias_us_; |
+ const int64_t kMinFrameIntervalUs = rtc::kNumMicrosecsPerMillisec; |
+ // Clip to make sure we don't produce timestamps in the future. |
+ int64_t time_us = filtered_time_us - clip_bias_us_; |
if (time_us > system_time_us) { |
clip_bias_us_ += time_us - system_time_us; |
time_us = system_time_us; |
} |
- prev_translated_time_us_ = rtc::Optional<int64_t>(time_us); |
+ // Make timestamps monotonic, with a minimum inter-frame interval of 1 ms. |
+ else if (time_us < prev_translated_time_us_ + kMinFrameIntervalUs) { |
+ time_us = prev_translated_time_us_ + kMinFrameIntervalUs; |
+ if (time_us > system_time_us) { |
+ // In the anomalous case that this function is called with values of |
+ // |system_time_us| less than |kMinFrameIntervalUs| apart, we may output |
+ // timestamps with with too short inter-frame interval. We may even return |
+ // duplicate timestamps in case this function is called several times with |
+ // exactly the same |system_time_us|. |
+ LOG(LS_WARNING) << "too short translated timestamp interval: " |
+ << "system time (us) = " << system_time_us |
+ << ", interval (us) = " |
+ << system_time_us - prev_translated_time_us_; |
+ time_us = system_time_us; |
+ } |
+ } |
+ RTC_DCHECK_GE(time_us, prev_translated_time_us_); |
+ RTC_DCHECK_LE(time_us, system_time_us); |
+ prev_translated_time_us_ = time_us; |
return time_us; |
} |