Highly optimized video decoding

still some problems with looping videos

Vocaluxe/Lib/Video/Acinerella/CDecoder.cs

@@ -18,9 +18,6 @@
 using System;
 using System.Diagnostics;
 using System.IO;
-using System.Runtime.InteropServices;
-using System.Threading;
-using Vocaluxe.Base;
 using VocaluxeLib.Draw;
 
 namespace Vocaluxe.Lib.Video.Acinerella
@@ -28,46 +25,54 @@ namespace Vocaluxe.Lib.Video.Acinerella
     class CDecoder
     {
         private readonly Stopwatch _LoopTimer = new Stopwatch();
-        private readonly Object _MutexSyncSignals = new Object();
 
-        private float _LastShownTime; // time if the last shown frame in s
-
-        private float _Time;
+        private float _LastShownTime = -1f; // time if the last shown frame in s
         private float _Gap;
-        private float _Start;
-        private bool _Loop;
-
-        private float _SetTime;
-        private float _SetGap;
-        private float _SetStart;
-        private bool _SetSkip;
-
-        private float _SkipTime; // = Start + VideoGap
-
-        private string _FileName; // current video file name
         private bool _Paused;
+        private float _LoopTime;
 
         private CDecoderThread _Thread;
-
-        public CDecoder() {}
-
         public float Length { get; private set; }
-
-        public bool Loop { private get; set; }
-
         public bool Finished { get; private set; }
 
+        public CDecoder()
+        {
+            Length = 0;
+            Finished = true;
+        }
+
+        public bool Loop
+        {
+            get { return _Thread.Loop; }
+            set
+            {
+                {
+                    _Thread.Loop = value;
+                    if (value)
+                    {
+                        _LoopTime = _Thread._RequestTime;
+                        _LoopTimer.Restart();
+                    }
+                }
+            }
+        }
+
         public bool Paused
         {
             set
             {
-                lock (_MutexSyncSignals)
+                if (_Paused == value)
+                    return;
+                _Paused = value;
+                if (_Paused)
                 {
-                    _Paused = value;
-                    if (_Paused)
-                        _LoopTimer.Stop();
-                    else
-                        _LoopTimer.Start();
+                    _LoopTimer.Stop();
+                    _Thread.Pause();
+                }
+                else
+                {
+                    _LoopTimer.Start();
+                    _Thread.Resume();
                 }
             }
         }
@@ -80,35 +85,15 @@ namespace Vocaluxe.Lib.Video.Acinerella
             if (!File.Exists(fileName))
                 return false;
 
-            _FileName = fileName;
-
-            //Do this here as one may want to get the length afterwards!
-            IntPtr pInstance = _LoadFile();
-            if (pInstance == IntPtr.Zero)
-                return false;
-
-
-            _Thread = new CDecoderThread(Path.GetFileName(fileName), pInstance);
-            return true;
-        }
-
-        //Open the file and get the length.
-        private IntPtr _LoadFile()
-        {
-            try
+            _Thread = new CDecoderThread();
+            if (_Thread.LoadFile(fileName))
             {
-                IntPtr pInstance = CAcinerella.AcInit();
-                CAcinerella.AcOpen2(pInstance, _FileName);
-
-                var instance = (SACInstance)Marshal.PtrToStructure(pInstance, typeof(SACInstance));
-                Length = instance.Info.Duration / 1000f;
-                bool ok = instance.Opened;
-                if (ok)
-                    return pInstance;
+                Length = _Thread.Length;
+                Finished = false;
+                return _Thread.Start();
             }
-            catch (Exception) {}
-            CLog.LogError("Error opening video file: " + _FileName);
-            return IntPtr.Zero;
+            _Thread = null;
+            return false;
         }
 
         public void Close()
@@ -116,45 +101,61 @@ namespace Vocaluxe.Lib.Video.Acinerella
             if (_Thread != null)
                 _Thread.Stop();
             Length = 0;
+            Finished = true;
         }
 
         public bool GetFrame(ref CTexture frame, float time, out float videoTime)
         {
+            if (Finished)
+            {
+                videoTime = Length - _Gap;
+                return false;
+            }
             if (Loop)
             {
-                lock (_MutexSyncSignals)
+                time = _LoopTime + _LoopTimer.ElapsedMilliseconds / 1000f;
+                if (time >= Length)
                 {
-                    _SetTime += _LoopTimer.ElapsedMilliseconds / 1000f;
+                    do
+                    {
+                        time -= Length;
+                    } while (time >= Length);
+                    _LoopTime = time;
                     _LoopTimer.Restart();
                 }
             }
-            else if (Math.Abs(_SetTime - time) >= 1f / 1000f) //Check 1 ms difference
+            else
+                time += _Gap;
+            _Thread.SyncTime(time);
+
+            if (Math.Abs(_LastShownTime - time) < 1f / 1000 && frame != null) //Check 1 ms difference
             {
-                lock (_MutexSyncSignals)
-                {
-                    _SetTime = time;
-                }
-            }
-            else if (Math.Abs(_LastShownTime - time) < 1f / 1000 && frame != null) //Check 1 ms difference
-            {
-                videoTime = _LastShownTime;
+                videoTime = _LastShownTime - _Gap;
                 return true;
             }
-            _UploadNewFrame(ref frame);
-            videoTime = _LastShownTime;
+            CDecoderThread.EFrameState state = _Thread.GetFrame(ref frame, ref time);
+            switch (state)
+            {
+                case CDecoderThread.EFrameState.EndFrame:
+                    Finished = true;
+                    videoTime = Length - _Gap;
+                    break;
+                case CDecoderThread.EFrameState.ValidFrame:
+                    _LastShownTime = time;
+                    videoTime = time - _Gap;
+                    break;
+                default:
+                    videoTime = _LastShownTime - _Gap;
+                    break;
+            }
             return frame != null;
         }
 
         public bool Skip(float start, float gap)
         {
-            lock (_MutexSyncSignals)
-            {
-                _SetStart = start;
-                _SetGap = gap;
-                _SetSkip = true;
-                _NoMoreFrames = false;
-                Finished = false;
-            }
+            Finished = false;
+            _Gap = gap;
+            _Thread.Skip(start + gap);
             return true;
         }
     }

Vocaluxe/Lib/Video/Acinerella/CDecoderThread.cs

@@ -1,51 +1,244 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
+using System.IO;
 using System.Runtime.InteropServices;
-using System.Text;
 using System.Threading;
 using Vocaluxe.Base;
 using VocaluxeLib.Draw;
 
 namespace Vocaluxe.Lib.Video.Acinerella
 {
+    //This class describes a thread decoding a video
+    //All public methods are meant to be called from "reader" thread only
+    //Most others are to be called by this thread  (_Thread instance) only!
     class CDecoderThread
     {
-        private readonly Thread _Thread;
-        private readonly Object _MutexFramebuffer = new Object();
-        private bool isStarted;
+        public enum EFrameState
+        {
+            ValidFrame,
+            InvalidFrame,
+            EndFrame
+        }
 
-        private IntPtr _Instance; // acinerella instance
+        private Thread _Thread;
+
+        private IntPtr _Instance = IntPtr.Zero; // acinerella instance
         private IntPtr _Videodecoder = IntPtr.Zero; // acinerella video decoder instance
 
         private readonly CFramebuffer _Framebuffer;
         private float _LastDecodedTime; // time of last decoded frame
+        // time of last requested frame aka current should-be position (_LastDecodedTime should be >=_RequestTime)
+        //HAS to be < Length
+        public float _RequestTime { get; private set; }
+        private bool _Paused;
 
+        private String _FileName;
         private float _FrameDuration; // frame time in s
         private int _Width;
         private int _Height;
 
+        private bool _RequestSkip;
         private bool _Terminated;
         private bool _FrameAvailable;
         private bool _NoMoreFrames;
         private readonly AutoResetEvent _EvWakeUp = new AutoResetEvent(false);
+        private readonly AutoResetEvent _EvPause = new AutoResetEvent(false);
+        private readonly AutoResetEvent _EvNoMoreFrames = new AutoResetEvent(false);
         private bool _IsSleeping;
         private int _WaitCount;
 
-        public CDecoderThread(String name, IntPtr instance)
+        public float Length { get; private set; }
+        public bool Loop { get; set; }
+
+        public CDecoderThread()
         {
             _Framebuffer = new CFramebuffer(10);
-            _Instance = instance;
-            _Thread = new Thread(_Execute) {Priority = ThreadPriority.Normal, Name = name};
+        }
+
+        //Open the file and get the length.
+        public bool LoadFile(String fileName)
+        {
+            _FileName = fileName;
+            try
+            {
+                _Instance = CAcinerella.AcInit();
+                CAcinerella.AcOpen2(_Instance, fileName);
+
+                var instance = (SACInstance)Marshal.PtrToStructure(_Instance, typeof(SACInstance));
+                Length = instance.Info.Duration / 1000f;
+                bool ok = instance.Opened && Length > 0.001f;
+                if (ok)
+                    return true;
+                _Free();
+            }
+            catch (Exception) {}
+            CLog.LogError("Error opening video file: " + _FileName);
+            _Instance = IntPtr.Zero;
+            return false;
+        }
+
+        public bool Start()
+        {
+            if (_Instance == IntPtr.Zero)
+            {
+                CLog.LogError("Tried to start a video file that is not open: " + _FileName);
+                return false;
+            }
+            if (_Thread != null)
+            {
+                CLog.LogError("Tried to start a video file that is already started: " + _FileName);
+                return false;
+            }
+            _RequestTime = 0f;
+            _Thread = new Thread(_Execute) {Priority = ThreadPriority.Normal, Name = Path.GetFileName(_FileName)};
             _Thread.Start();
+            return true;
         }
 
         public void Stop()
         {
             _Terminated = true;
+            _EvPause.Set();
+            _EvWakeUp.Set();
+            _EvNoMoreFrames.Set();
         }
 
-        private bool _DoOpen()
+        public void Pause()
+        {
+            if (_Paused)
+                return;
+            _EvPause.Reset();
+            _Paused = true;
+        }
+
+        public void Resume()
+        {
+            if (!_Paused)
+                return;
+            _Paused = false;
+            _EvPause.Set();
+        }
+
+        public void Skip(float time)
+        {
+            //TODO: Problem: This is not threadsave
+            //Scenario: Clear buffer from main thread, decoder is in _Decode or _Copy
+            //Result: Cleared buffer contains 1 old item. This is a problem when skipping back: E.g. Loop:
+            //Old item has time=Length->Will not get removed
+            //Workaround: Check in _FindFrame to remove first old item
+            _Framebuffer.Clear();
+
+
+            _RequestTime = time;
+            _RequestSkip = true;
+            _EvNoMoreFrames.Set();
+        }
+
+        private CFramebuffer.CFrame _FindFrame(float now)
+        {
+            CFramebuffer.CFrame result = null;
+            float maxEnd = now - _FrameDuration * 2; //Get only frames younger than 2
+            CFramebuffer.CFrame frame;
+            bool first = true;
+            _Framebuffer.ResetStack();
+            while ((frame = _Framebuffer.Pop()) != null)
+            {
+                float frameEnd = frame.Time + _FrameDuration;
+                //Don't show frames that are shown during or after now
+                if (frameEnd >= now)
+                {
+                    //All following frames are after that one -> BREAK
+                    if (!first)
+                        break;
+                    //Well... Should be. Workaround:
+                    CFramebuffer.CFrame nextFrame = _Framebuffer.Pop();
+                    if (nextFrame == null || nextFrame.Time > frame.Time)
+                        break;
+                    frame.SetRead(); //Discard wrong frame
+                    frame = nextFrame;
+                    //Replicate calculations
+                    frameEnd = frame.Time + _FrameDuration;
+                    if (frameEnd >= now)
+                        break;
+                }
+                first = false;
+                //Get the last(newest) possible frame and skip the rest to force in-order showing
+                if (frameEnd <= maxEnd)
+                {
+                    //Frame is to old -> Discard
+                    frame.SetRead();
+                }
+                else
+                {
+                    maxEnd = frameEnd;
+                    result = frame;
+                }
+            }
+            return result;
+        }
+
+        //Time should be < Length
+        public void SyncTime(float time)
+        {
+            if (_Thread == null)
+                return; //Not initialized
+            while (time >= Length)
+                time -= Length;
+            if (_RequestTime - time >= 1f / 1000f)
+            {
+                //Jump back more than 1ms
+                //Will mostly happen in loops when looped through
+                Skip(time);
+            }
+            else if (time - _RequestTime >= 1f / 1000f)
+            {
+                //we were more than 1 ms to slow -> Jump forward
+                // ReSharper disable CompareOfFloatsByEqualityOperator
+                if (Loop && _RequestTime == 0f)
+                    // ReSharper restore CompareOfFloatsByEqualityOperator
+                {
+                    //Check if we had a loop
+                    _Framebuffer.ResetStack();
+                    CFramebuffer.CFrame frame;
+                    while ((frame = _Framebuffer.Pop()) != null)
+                    {
+                        if (frame.Time + _FrameDuration >= time)
+                            return;
+                    }
+                }
+
+                _RequestTime = time;
+            }
+        }
+
+        public EFrameState GetFrame(ref CTexture frame, ref float time)
+        {
+            EFrameState result;
+            CFramebuffer.CFrame curFrame = _FindFrame(time);
+
+            if (curFrame != null)
+            {
+                CDraw.UpdateOrAddTexture(ref frame, _Width, _Height, curFrame.Data);
+                if (!_Paused)
+                    curFrame.SetRead();
+                time = curFrame.Time;
+                result = (frame != null) ? EFrameState.ValidFrame : EFrameState.InvalidFrame;
+            }
+            else
+            {
+                if (_NoMoreFrames && _Framebuffer.IsEmpty())
+                    result = EFrameState.EndFrame;
+                else
+                    result = EFrameState.InvalidFrame;
+            }
+            if (_IsSleeping)
+            {
+                _IsSleeping = false;
+                _EvWakeUp.Set();
+            }
+            return result;
+        }
+
+        private bool _OpenVideoStream()
         {
             int videoStreamIndex;
             SACDecoder videodecoder;
@@ -57,16 +250,12 @@ namespace Vocaluxe.Lib.Video.Acinerella
             }
             catch (Exception)
             {
-                CLog.LogError("Error opening video file (can't find decoder): " + _Thread.Name);
-                _Free();
+                CLog.LogError("Error opening video file (can't find decoder): " + _FileName);
                 return false;
             }
 
             if (videoStreamIndex < 0)
-            {
-                _Free();
                 return false;
-            }
 
             _Width = videodecoder.StreamInfo.VideoInfo.FrameWidth;
             _Height = videodecoder.StreamInfo.VideoInfo.FrameHeight;
@@ -74,14 +263,12 @@ namespace Vocaluxe.Lib.Video.Acinerella
             if (videodecoder.StreamInfo.VideoInfo.FramesPerSecond > 0)
                 _FrameDuration = 1f / (float)videodecoder.StreamInfo.VideoInfo.FramesPerSecond;
 
-            _LastDecodedTime = 0f;
-            _SetTime = 0f;
-
             _Framebuffer.Init(_Width * _Height * 4);
             _FrameAvailable = false;
             return true;
         }
 
+        //Just call this if thread is not alive
         private void _Free()
         {
             if (_Videodecoder != IntPtr.Zero)
@@ -94,50 +281,108 @@ namespace Vocaluxe.Lib.Video.Acinerella
             }
         }
 
+        // Skip to a given time (in s)
         private void _Skip()
         {
-            _SkipTime = _Start + _Gap;
-
-            if (_SkipTime < 0)
-                _SkipTime = 0;
+            float skipTime = _RequestTime;
+            if (skipTime < 0 || skipTime >= Length)
+                skipTime = 0;
 
             try
             {
-                CAcinerella.AcSeek(_Videodecoder, -1, (Int64)(_SkipTime * 1000f));
+                CAcinerella.AcSeek(_Videodecoder, -1, (Int64)(skipTime * 1000f));
             }
             catch (Exception e)
             {
                 CLog.LogError("Error seeking video file \"" + _FileName + "\": " + e.Message);
             }
-            _LastDecodedTime = _SkipTime;
+            _LastDecodedTime = skipTime;
 
-            lock (_MutexFramebuffer)
+            _FrameAvailable = false;
+        }
+
+        private void _Decode()
+        {
+            const int minFrameDropCount = 4;
+
+            if (_Paused || _NoMoreFrames)
+                return;
+
+            float videoTime = _RequestTime;
+            float timeDifference = videoTime - _LastDecodedTime;
+
+            bool dropFrame = timeDifference >= (minFrameDropCount - 1) * _FrameDuration;
+
+            bool hasFrameDecoded = false;
+            if (dropFrame)
             {
-                _Framebuffer.Clear();
+                try
+                {
+                    var frameDropCount = (int)(timeDifference / _FrameDuration);
+                    hasFrameDecoded = CAcinerella.AcSkipFrames(_Instance, _Videodecoder, frameDropCount);
+                }
+                catch (Exception)
+                {
+                    CLog.LogError("Error AcSkipFrame " + _FileName);
+                }
             }
 
+            if (!hasFrameDecoded)
+            {
+                try
+                {
+                    hasFrameDecoded = CAcinerella.AcGetFrame(_Instance, _Videodecoder);
+                }
+                catch (Exception)
+                {
+                    CLog.LogError("Error AcGetFrame " + _FileName);
+                }
+            }
+            if (hasFrameDecoded)
+                _FrameAvailable = true;
+            else
+            {
+                if (Loop)
+                {
+                    _RequestTime = 0;
+                    _Skip();
+                }
+                else
+                    _NoMoreFrames = true;
+            }
+        }
+
+        private void _CopyDecodedFrameToBuffer()
+        {
+            var videodecoder = (SACDecoder)Marshal.PtrToStructure(_Videodecoder, typeof(SACDecoder));
+            if (videodecoder.Buffer != IntPtr.Zero)
+            {
+                _LastDecodedTime = (float)videodecoder.Timecode;
+                _Framebuffer.Put(videodecoder.Buffer, _LastDecodedTime);
+            }
             _FrameAvailable = false;
         }
 
         private void _Execute()
         {
-            if (!_DoOpen())
+            if (!_OpenVideoStream())
+            {
+                _Free();
                 Stop();
+            }
+
             while (!_Terminated)
             {
-                bool skip;
-                lock (_MutexSyncSignals)
+                if (_Paused)
+                    _EvPause.WaitOne();
+                if (_NoMoreFrames)
+                    _EvNoMoreFrames.WaitOne();
+                if (_RequestSkip)
                 {
-                    _Time = _SetTime;
-                    skip = _SetSkip;
-                    _SetSkip = false;
-                    _Gap = _SetGap;
-                    _Start = _SetStart;
-                    _Loop = Loop;
-                }
-
-                if (skip)
+                    _RequestSkip = false;
+                    _NoMoreFrames = false;
                     _Skip();
+                }
 
                 if (!_FrameAvailable)
                     _Decode();
@@ -146,9 +391,9 @@ namespace Vocaluxe.Lib.Video.Acinerella
                 {
                     if (!_Framebuffer.IsFull())
                     {
-                        _Copy();
+                        _CopyDecodedFrameToBuffer();
                         _WaitCount = 0;
-                        Thread.Sleep(1);
+                        Thread.Sleep(5);
                     }
                     else if (_WaitCount > 3)
                     {
@@ -165,148 +410,5 @@ namespace Vocaluxe.Lib.Video.Acinerella
 
             _Free();
         }
-
-        private void _Decode()
-        {
-            const int minFrameDropCount = 4;
-
-            if (_Paused || _NoMoreFrames)
-                return;
-
-            float videoTime = _Time + _Gap;
-            float timeDifference = videoTime - _LastDecodedTime;
-
-            bool dropFrame = timeDifference >= (minFrameDropCount - 1) * _FrameDuration;
-
-            if (_Terminated)
-                return;
-
-            bool frameFinished = false;
-            if (dropFrame)
-            {
-                try
-                {
-                    if (videoTime >= Length)
-                    {
-                        if (_Loop)
-                        {
-                            lock (_MutexSyncSignals)
-                            {
-                                _Start = 0;
-                                _Gap = 0f;
-                                _SetTime = 0;
-                            }
-                            _Skip();
-                        }
-                        else
-                        {
-                            _NoMoreFrames = true;
-                            return;
-                        }
-                    }
-                    else
-                    {
-                        var frameDropCount = (int)(timeDifference / _FrameDuration);
-                        frameFinished = CAcinerella.AcSkipFrames(_Instance, _Videodecoder, frameDropCount);
-                    }
-                }
-                catch (Exception)
-                {
-                    CLog.LogError("Error AcSkipFrame " + _Thread.Name);
-                }
-            }
-
-            if (!frameFinished)
-            {
-                try
-                {
-                    frameFinished = CAcinerella.AcGetFrame(_Instance, _Videodecoder);
-                }
-                catch (Exception)
-                {
-                    CLog.LogError("Error AcGetFrame " + _Thread.Name);
-                }
-            }
-            if (frameFinished)
-                _FrameAvailable = true;
-            else
-            {
-                if (_Loop)
-                {
-                    lock (_MutexSyncSignals)
-                    {
-                        _Start = 0f;
-                        _Gap = 0f;
-                        _SetTime = 0f;
-                    }
-                    _Skip();
-                }
-                else
-                    _NoMoreFrames = true;
-            }
-        }
-
-        private void _Copy()
-        {
-            var videodecoder = (SACDecoder)Marshal.PtrToStructure(_Videodecoder, typeof(SACDecoder));
-            if (videodecoder.Buffer == IntPtr.Zero)
-                return;
-            _LastDecodedTime = (float)videodecoder.Timecode;
-            _Framebuffer.Put(videodecoder.Buffer, _LastDecodedTime);
-            _FrameAvailable = false;
-        }
-
-        private void _UploadNewFrame(ref CTexture frame)
-        {
-            lock (_MutexFramebuffer)
-            {
-                CFrame curFrame = _FindFrame();
-
-                if (curFrame != null)
-                {
-                    CDraw.UpdateOrAddTexture(ref frame, _Width, _Height, curFrame.Data);
-
-                    lock (_MutexSyncSignals)
-                    {
-                        _LastShownTime = curFrame.Time;
-                    }
-                }
-                else
-                {
-                    if (_NoMoreFrames && _Framebuffer.IsEmpty())
-                        Finished = true;
-                }
-            }
-            if (!Finished && _IsSleeping)
-            {
-                _IsSleeping = false;
-                _EvWakeUp.Set();
-            }
-        }
-
-        private CFrame _FindFrame()
-        {
-            CFrame result = null;
-            float now = _SetTime + _Gap;
-            float maxEnd = now - _FrameDuration * 2; //Get only frames younger than 2
-            CFrame frame;
-            bool paused = _Paused;
-            while ((frame = _Framebuffer.Get()) != null)
-            {
-                float frameEnd = frame.Time + _FrameDuration;
-                //Don't show frames that are shown during or after now
-                if (frameEnd >= now)
-                    break; //All following frames are after that one
-                if (paused) // Don't modify anything
-                    break;
-                _Framebuffer.SetRead();
-                //Get the last(newest) possible frame and skip the rest to force in-order showing
-                if (frameEnd <= maxEnd)
-                    continue;
-                maxEnd = frameEnd;
-                result = frame;
-            }
-            return result;
-        }
     }
 }

Vocaluxe/Lib/Video/Acinerella/CFramebuffer.cs

@@ -20,24 +20,35 @@ using System.Runtime.InteropServices;
 
 namespace Vocaluxe.Lib.Video.Acinerella
 {
-    class CFrame
-    {
-        public readonly byte[] Data;
-        public float Time = -1;
-
-        public CFrame(int dataSize)
-        {
-            Data = new byte[dataSize];
-        }
-    }
-
     class CFramebuffer
     {
+        public class CFrame
+        {
+            private readonly CFramebuffer _Parent;
+            private readonly int _Index;
+            public readonly byte[] Data;
+            public float Time = -1;
+
+            public CFrame(CFramebuffer parent, int index, int dataSize)
+            {
+                _Parent = parent;
+                _Index = index;
+                Data = new byte[dataSize];
+            }
+
+            //Only call from reader thread
+            public void SetRead()
+            {
+                _Parent._SetRead(_Index);
+            }
+        }
+
         private readonly CFrame[] _Frames;
         private readonly int _Size;
         private int _DataSize;
         private int _Last;
         private int _First;
+        private int _Next;
         private bool _Initialized;
 
         public int Size
@@ -45,21 +56,24 @@ namespace Vocaluxe.Lib.Video.Acinerella
             get { return _Size; }
         }
 
+        // Constructs a framebuffer with max. size frames
         public CFramebuffer(int size)
         {
             _Size = size;
             _Frames = new CFrame[size];
         }
 
+        // Initializes the framebuffer with the size of each frame
+        // MUST be called before all others
         public void Init(int dataSize)
         {
             _DataSize = dataSize;
             for (int i = 0; i < _Size; i++)
-                _Frames[i] = new CFrame(dataSize);
+                _Frames[i] = new CFrame(this, i, dataSize);
             _Initialized = true;
         }
 
-        private int _Next(int current)
+        private int _GetNextIndex(int current)
         {
             current++;
             return (current < _Size) ? current : 0;
@@ -67,7 +81,7 @@ namespace Vocaluxe.Lib.Video.Acinerella
 
         public bool IsFull()
         {
-            return _Next(_Last) == _First;
+            return _GetNextIndex(_Last) == _First;
         }
 
         public bool IsEmpty()
@@ -75,6 +89,7 @@ namespace Vocaluxe.Lib.Video.Acinerella
             return _First == _Last;
         }
 
+        //Only call from writer thread
         public bool Put(IntPtr data, float time)
         {
             if (!_Initialized || IsFull())
@@ -82,27 +97,38 @@ namespace Vocaluxe.Lib.Video.Acinerella
             CFrame frame = _Frames[_Last];
             Marshal.Copy(data, frame.Data, 0, _DataSize);
             frame.Time = time;
-            _Last = _Next(_Last);
+            _Last = _GetNextIndex(_Last);
             return true;
         }
 
-        public CFrame Get()
+        //Only call from reader thread
+        public void ResetStack()
         {
-            return IsEmpty() ? null : _Frames[_First];
+            _Next = _First;
         }
 
-        public bool SetRead()
+        //Pops the next frame if available
+        //You have to call ResetNext before the first call to this function and call the CFrame.SetRead to free the buffers
+        //Only call from reader thread
+        public CFrame Pop()
         {
-            if (IsEmpty())
-                return false;
-            _First = _Next(_First);
-            return true;
+            if (_Next == _Last)
+                return null;
+            CFrame res = _Frames[_Next];
+            _Next = _GetNextIndex(_Next);
+            return res;
         }
 
+        private void _SetRead(int index)
+        {
+            if ((_First < index && (index < _Next || _Next < _First)) || (_Next < _First && index < _Next))
+                _First = _GetNextIndex(index);
+        }
+
+        //Only call from reader thread
         public void Clear()
         {
-            _First = 0;
-            _Last = 0;
+            _Next = _First = _Last;
         }
     }
 }