Allow usage of non-allocating frame buffers

LavalinkServer/application.yml.example

@@ -38,6 +38,7 @@ lavalink:
       rotation: true
       channelMix: true
       lowPass: true
+    nonAllocatingFrameBuffer: false # Setting to true reduces the number of allocations made by each player at the expense of frame rebuilding (e.g. non-instantaneous volume changes)
     bufferDurationMs: 400 # The duration of the NAS buffer. Higher values fare better against longer GC pauses. Duration <= 0 to disable JDA-NAS. Minimum of 40ms, lower values may introduce pauses.
     frameBufferDurationMs: 5000 # How many milliseconds of audio to keep buffered
     opusEncodingQuality: 10 # Opus encoder quality. Valid values range from 0 to 10, where 10 is best quality but is the most expensive on the CPU.

LavalinkServer/src/main/java/lavalink/server/config/AudioPlayerConfiguration.kt

@@ -14,6 +14,7 @@ import com.sedmelluq.discord.lavaplayer.source.soundcloud.*
 import com.sedmelluq.discord.lavaplayer.source.twitch.TwitchStreamAudioSourceManager
 import com.sedmelluq.discord.lavaplayer.source.vimeo.VimeoAudioSourceManager
 import com.sedmelluq.discord.lavaplayer.source.youtube.YoutubeAudioSourceManager
+import com.sedmelluq.discord.lavaplayer.track.playback.NonAllocatingAudioFrameBuffer
 import com.sedmelluq.lava.extensions.youtuberotator.YoutubeIpRotatorSetup
 import com.sedmelluq.lava.extensions.youtuberotator.planner.*
 import com.sedmelluq.lava.extensions.youtuberotator.tools.ip.Ipv4Block
@@ -55,6 +56,11 @@ class AudioPlayerConfiguration {
             audioPlayerManager.enableGcMonitoring()
         }
 
+        if (serverConfig.isNonAllocatingFrameBuffer) {
+            log.info("Using a non-allocating frame buffer")
+            audioPlayerManager.configuration.setFrameBufferFactory(::NonAllocatingAudioFrameBuffer)
+        }
+
         val defaultFrameBufferDuration = audioPlayerManager.frameBufferDuration
         serverConfig.frameBufferDurationMs?.let {
             if (it < 200) { // At the time of writing, LP enforces a minimum of 200ms.

LavalinkServer/src/main/java/lavalink/server/config/ServerConfig.kt

@@ -30,6 +30,7 @@ import org.springframework.stereotype.Component
 @Component
 class ServerConfig {
     var password: String? = null
+    var isNonAllocatingFrameBuffer = false
     var bufferDurationMs: Int? = null
     var frameBufferDurationMs: Int? = null
     var opusEncodingQuality: Int? = null

LavalinkServer/src/main/java/lavalink/server/player/LavalinkPlayer.kt

@@ -21,12 +21,14 @@
  */
 package lavalink.server.player
 
+import com.sedmelluq.discord.lavaplayer.format.StandardAudioDataFormats
 import com.sedmelluq.discord.lavaplayer.player.AudioPlayer
 import com.sedmelluq.discord.lavaplayer.player.AudioPlayerManager
 import com.sedmelluq.discord.lavaplayer.player.event.AudioEventAdapter
 import com.sedmelluq.discord.lavaplayer.track.AudioTrack
 import com.sedmelluq.discord.lavaplayer.track.AudioTrackEndReason
 import com.sedmelluq.discord.lavaplayer.track.playback.AudioFrame
+import com.sedmelluq.discord.lavaplayer.track.playback.MutableAudioFrame
 import dev.arbjerg.lavalink.api.AudioPluginInfoModifier
 import dev.arbjerg.lavalink.api.IPlayer
 import io.netty.buffer.ByteBuf
@@ -36,6 +38,7 @@ import lavalink.server.io.SocketServer.Companion.sendPlayerUpdate
 import lavalink.server.player.filters.FilterChain
 import moe.kyokobot.koe.MediaConnection
 import moe.kyokobot.koe.media.OpusAudioFrameProvider
+import java.nio.ByteBuffer
 import java.util.concurrent.ScheduledFuture
 import java.util.concurrent.TimeUnit
 
@@ -46,6 +49,9 @@ class LavalinkPlayer(
     audioPlayerManager: AudioPlayerManager,
     pluginInfoModifiers: List<AudioPluginInfoModifier>
 ) : AudioEventAdapter(), IPlayer {
+    private val buffer = ByteBuffer.allocate(StandardAudioDataFormats.DISCORD_OPUS.maximumChunkSize())
+    private val mutableFrame = MutableAudioFrame().apply { setBuffer(buffer) }
+
     val audioLossCounter = AudioLossCounter()
     var endMarkerHit = false
     var filters: FilterChain = FilterChain()
@@ -117,21 +123,15 @@ class LavalinkPlayer(
     }
 
     private inner class Provider(connection: MediaConnection?) : OpusAudioFrameProvider(connection) {
-        private var lastFrame: AudioFrame? = null
-
-        override fun canProvide(): Boolean {
-            lastFrame = audioPlayer.provide()
-            return if (lastFrame == null) {
+        override fun canProvide() = audioPlayer.provide(mutableFrame).also { provided ->
+            if (!provided) {
                 audioLossCounter.onLoss()
-                false
-            } else {
-                true
             }
         }
 
         override fun retrieveOpusFrame(buf: ByteBuf) {
             audioLossCounter.onSuccess()
-            buf.writeBytes(lastFrame!!.data)
+            buf.writeBytes(buffer.flip())
         }
     }
 }