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Updated UTCTiming Clock synchronization (markdown) authored by Daniel Silhavy's avatar Daniel Silhavy
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UTCTiming---Clock-synchronization.md
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......@@ -60,7 +60,7 @@ An MPD update triggers an event to attempt a clock synchronization. The `TimeSyn
```javascript
function _shouldPerformSynchronization() {
try {
const timeBetweenSyncAttempts = settings.get().streaming.utcSynchronization.timeBetweenSyncAttempts;
const timeBetweenSyncAttempts = !isNaN(internalTimeBetweenSyncAttempts) ? internalTimeBetweenSyncAttempts : DEFAULT_TIME_BETWEEN_SYNC_ATTEMPTS;
if (!timeOfLastSync || !timeBetweenSyncAttempts || isNaN(timeBetweenSyncAttempts)) {
return true;
......@@ -87,13 +87,12 @@ player.updateSettings({
})
```
#### Post-synchronization parameter adjustment
After each regular synchronization attempt, dash.js adjusts the `timeBetweenSyncAttempts` parameter based on certain criteria:
After each regular synchronization attempt, dash.js adjusts its internal `internalTimeBetweenSyncAttempts` parameter based on certain criteria:
```javascript
function _adjustTimeBetweenSyncAttempts(offset) {
try {
const isOffsetDriftWithinThreshold = _isOffsetDriftWithinThreshold(offset);
const timeBetweenSyncAttempts = !isNaN(settings.get().streaming.utcSynchronization.timeBetweenSyncAttempts) ? settings.get().streaming.utcSynchronization.timeBetweenSyncAttempts : DEFAULT_TIME_BETWEEN_SYNC_ATTEMPTS;
const timeBetweenSyncAttempts = !isNaN(internalTimeBetweenSyncAttempts) ? internalTimeBetweenSyncAttempts : DEFAULT_TIME_BETWEEN_SYNC_ATTEMPTS;
const timeBetweenSyncAttemptsAdjustmentFactor = !isNaN(settings.get().streaming.utcSynchronization.timeBetweenSyncAttemptsAdjustmentFactor) ? settings.get().streaming.utcSynchronization.timeBetweenSyncAttemptsAdjustmentFactor : DEFAULT_TIME_BETWEEN_SYNC_ATTEMPTS_ADJUSTMENT_FACTOR;
const maximumTimeBetweenSyncAttempts = !isNaN(settings.get().streaming.utcSynchronization.maximumTimeBetweenSyncAttempts) ? settings.get().streaming.utcSynchronization.maximumTimeBetweenSyncAttempts : DEFAULT_MAXIMUM_TIME_BETWEEN_SYNC;
const minimumTimeBetweenSyncAttempts = !isNaN(settings.get().streaming.utcSynchronization.minimumTimeBetweenSyncAttempts) ? settings.get().streaming.utcSynchronization.minimumTimeBetweenSyncAttempts : DEFAULT_MINIMUM_TIME_BETWEEN_SYNC;
......@@ -109,11 +108,7 @@ After each regular synchronization attempt, dash.js adjusts the `timeBetweenSync
logger.debug(`Decreasing timeBetweenSyncAttempts to ${adjustedTimeBetweenSyncAttempts}`);
}
settings.update({ streaming: { utcSynchronization: { timeBetweenSyncAttempts: adjustedTimeBetweenSyncAttempts } } });
} catch (e) {
}
}
internalTimeBetweenSyncAttempts = adjustedTimeBetweenSyncAttempts;
```
In the first step the player checks if the offset is within certain boundaries:
......@@ -137,7 +132,7 @@ In the first step the player checks if the offset is within certain boundaries:
}
```
Depending on whether the offset is included in the calculated boundaries, `timeBetweenSyncAttempts` is either multiplied or divided by `timeBetweenSyncAttemptsAdjustmentFactor`. By assigning specific values to `maximumTimeBetweenSyncAttempts` and `minimumTimeBetweenSyncAttempts` upper and lower bounds for `timeBetweenSyncAttempts` can be set.
Depending on whether the offset is included in the calculated boundaries, `adjustedTimeBetweenSyncAttempts` is derived by either multiplying or dividing the current `internalTimeBetweenSyncAttempts` by `timeBetweenSyncAttemptsAdjustmentFactor`. By assigning specific values to `maximumTimeBetweenSyncAttempts` and `minimumTimeBetweenSyncAttempts` upper and lower bounds for `internalTimeBetweenSyncAttempts` can be set.
The parameters can be adjusted in the settings:
```javascript
......@@ -186,7 +181,7 @@ The available configuration parameters:
| Parameter | Description |
| ------------- |:-------------:|
| backgroundAttempts | Number of synchronization attempts to perform in the background after an initial synchronization request has been done. This is used to verify that the derived client-server offset is correct. |
| timeBetweenSyncAttempts | The time in seconds between two consecutive sync attempts. |
| timeBetweenSyncAttempts | The time in seconds between two consecutive sync attempts. Note: This value is used as an initial starting value. The internal value of the TimeSyncController is adjusted during playback based on the drift between two consecutive synchronization attempts. |
| maximumTimeBetweenSyncAttempts | The maximum time in seconds between two consecutive sync attempts. |
| minimumTimeBetweenSyncAttempts | The minimum time in seconds between two consecutive sync attempts|
| timeBetweenSyncAttemptsAdjustmentFactor | The factor used to multiply or divide the timeBetweenSyncAttempts parameter after a sync. The maximumAllowedDrift defines whether this value is used as a factor or a dividend. |
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