Allow configuring adaptive buffering by passing config object as `buf…

…ferTime` driver option
asciinema · Apr 27, 2024 · 0950a6d · 0950a6d
1 parent c0cfdc1
commit 0950a6d
Showing 1 changed file with 18 additions and 24 deletions.
diff --git a/src/buffer.js b/src/buffer.js
@@ -5,6 +5,7 @@ function getBuffer(bufferTime, feed, setTime, baseStreamTime, minFrameTime, logg
     logger.debug("using no buffer");
     return nullBuffer(feed);
   } else {
+    bufferTime = bufferTime ?? {};
     let getBufferTime;
 
     if (typeof bufferTime === "number") {
@@ -14,8 +15,8 @@ function getBuffer(bufferTime, feed, setTime, baseStreamTime, minFrameTime, logg
       logger.debug("using custom dynamic buffer");
       getBufferTime = bufferTime({ logger });
     } else {
-      logger.debug("using adaptive buffer");
-      getBufferTime = adaptiveBufferTimeProvider({ logger });
+      logger.debug("using adaptive buffer", bufferTime);
+      getBufferTime = adaptiveBufferTimeProvider({ logger }, bufferTime);
     }
 
     return buffer(getBufferTime, feed, setTime, logger, baseStreamTime ?? 0.0, minFrameTime);
@@ -117,41 +118,42 @@ function sleep(t) {
   });
 }
 
-const MIN_BUFFER_TIME = 25;
-const MAX_BUFFER_LEVEL = 100;
-const BUFFER_TIME_MULTIPLIER = 50;
-const LATENCY_WINDOW_SIZE = 20;
-const SMOOTHING_FACTOR = 0.2;
-const MIN_IMPROVEMENT_DURATION = 1000;
-
-function adaptiveBufferTimeProvider({ logger }) {
+function adaptiveBufferTimeProvider({ logger }, { minTime = 25, maxLevel = 100, interval = 50, windowSize = 20, smoothingFactor = 0.2, minImprovementDuration = 1000 }) {
   let bufferLevel = 0;
   let bufferTime = calcBufferTime(bufferLevel);
   let latencies = [];
   let maxJitter = 0;
   let jitterRange = 0;
   let improvementTs = null;
 
+  function calcBufferTime(level) {
+    if (level === 0) {
+      return minTime;
+    } else {
+      return interval * level;
+    }
+  }
+
   return (latency) => {
     latencies.push(latency);
 
-    if (latencies.length < LATENCY_WINDOW_SIZE) {
+    if (latencies.length < windowSize) {
       return bufferTime;
     };
 
-    latencies = latencies.slice(-LATENCY_WINDOW_SIZE);
+    latencies = latencies.slice(-windowSize);
     const currentMinJitter = min(latencies);
     const currentMaxJitter = max(latencies);
     const currentJitterRange = currentMaxJitter - currentMinJitter;
-    maxJitter = currentMaxJitter * SMOOTHING_FACTOR + maxJitter * (1 - SMOOTHING_FACTOR);
-    jitterRange = currentJitterRange * SMOOTHING_FACTOR + jitterRange * (1 - SMOOTHING_FACTOR);
+    maxJitter = currentMaxJitter * smoothingFactor + maxJitter * (1 - smoothingFactor);
+    jitterRange = currentJitterRange * smoothingFactor + jitterRange * (1 - smoothingFactor);
     const minBufferTime = maxJitter + jitterRange;
 
     if (latency > bufferTime) {
       logger.debug('buffer underrun', { latency, maxJitter, jitterRange, bufferTime });
     }
 
-    if (bufferLevel < MAX_BUFFER_LEVEL && minBufferTime > bufferTime) {
+    if (bufferLevel < maxLevel && minBufferTime > bufferTime) {
         bufferTime = calcBufferTime((bufferLevel += 1));
         logger.debug(`jitter increased, raising bufferTime`, { latency, maxJitter, jitterRange, bufferTime });
     } else if (
@@ -160,7 +162,7 @@ function adaptiveBufferTimeProvider({ logger }) {
     ) {
       if (improvementTs === null) {
         improvementTs = performance.now();
-      } else if (performance.now() - improvementTs > MIN_IMPROVEMENT_DURATION) {
+      } else if (performance.now() - improvementTs > minImprovementDuration) {
         improvementTs = performance.now();
         bufferTime = calcBufferTime((bufferLevel -= 1));
         logger.debug(`jitter decreased, lowering bufferTime`, { latency, maxJitter, jitterRange, bufferTime });
@@ -183,12 +185,4 @@ function max(numbers) {
   return numbers.reduce((prev, cur) => cur > prev ? cur : prev);
 }
 
-function calcBufferTime(level) {
-  if (level === 0) {
-    return MIN_BUFFER_TIME;
-  } else {
-    return BUFFER_TIME_MULTIPLIER * level;
-  }
-}
-
 export default getBuffer;