Reduce Android call playback startup buffering and log output queue

tools/chatgui-android/app/src/main/java/com/utun/chat/data/CallAudioEngine.kt

@@ -9,6 +9,7 @@ import android.media.AudioRecord
 import android.media.AudioTimestamp
 import android.media.AudioTrack
 import android.media.MediaRecorder
+import android.os.Build
 import android.os.Handler
 import android.os.Looper
 import android.os.SystemClock
@@ -175,6 +176,14 @@ class CallAudioEngine {
                         return@runWorker
                     }
                     applyTrackOutputDevice(router.currentOutputDevice)
+                    // Ёмкость устройства не должна становиться постоянной задержкой звонка.
+                    // Два блока оставляют запас на пробуждение playback-потока каждые 20 мс.
+                    val startFrames = FRAME_SAMPLES * 2
+                    val actualStart = if (Build.VERSION.SDK_INT >= 31) track.setStartThresholdInFrames(startFrames)
+                        else track.setBufferSizeInFrames(startFrames)
+                    LogManager.addLog(if (actualStart > 0) "INFO" else "WARN", "CallAudio",
+                        "playback buffering id=$id requestedStart=$startFrames actualStart=$actualStart " +
+                            "bufferFrames=${track.bufferSizeInFrames} capacityFrames=${track.bufferCapacityInFrames}")
                     val trackCreateMs = SystemClock.elapsedRealtime() - createdAt
                     val playedAt = SystemClock.elapsedRealtime()
                     track.play()
@@ -431,6 +440,7 @@ class CallAudioEngine {
         val head = CallPlaybackHead()
         var clockFailed = false
         var logAtUs = 0L
+        var lastUnderruns = 0
         while (active) {
             val track = audioTrack ?: return
             val n = NativeLib.callAudioPull(callId, buf)
@@ -474,9 +484,14 @@ class CallAudioEngine {
                 }
                 if (nowUs - logAtUs >= 1_000_000 && NativeLib.callAudioClock(callId, nowUs, snapshot)) {
                     logAtUs = nowUs
-                    LogManager.addLog("DEBUG", "CallAudio",
+                    val underruns = track.underrunCount
+                    val threshold = if (Build.VERSION.SDK_INT >= 31) track.startThresholdInFrames else track.bufferSizeInFrames
+                    val queuedUs = (snapshot[3] - snapshot[2]).coerceAtLeast(0) * 1_000_000 / SAMPLE_RATE
+                    LogManager.addLog(if (underruns > lastUnderruns) "WARN" else "DEBUG", "CallAudio",
                         "clock epoch=${snapshot[0]} source=${snapshot[1]} played=${snapshot[2]} written=${snapshot[3]} " +
-                            "ptsUs=${snapshot[4]} valid=${snapshot[5]} measured=${snapshot[6]} heldUs=${snapshot[7]}")
+                            "ptsUs=${snapshot[4]} valid=${snapshot[5]} measured=${snapshot[6]} heldUs=${snapshot[7]} " +
+                            "queuedUs=$queuedUs bufferFrames=${track.bufferSizeInFrames} startFrames=$threshold underruns=$underruns")
+                    lastUnderruns = underruns
                 }
             }