diff --git a/CUETools.FlaCuda/FlaCudaWriter.cs b/CUETools.FlaCuda/FlaCudaWriter.cs
index 73afe81..2c592c4 100644
--- a/CUETools.FlaCuda/FlaCudaWriter.cs
+++ b/CUETools.FlaCuda/FlaCudaWriter.cs
@@ -94,16 +94,18 @@ namespace CUETools.Codecs.FlaCuda
 
 		CUDA cuda;
 		CUfunction cudaComputeAutocor;
+		CUfunction cudaComputeLPC;
 		CUfunction cudaEncodeResidual;
 		CUdeviceptr cudaSamples;
 		CUdeviceptr cudaWindow;
 		CUdeviceptr cudaAutocorTasks;
 		CUdeviceptr cudaAutocorOutput;
+		CUdeviceptr cudaCompLPCOutput;
 		CUdeviceptr cudaResidualTasks;
 		CUdeviceptr cudaResidualOutput;
 		IntPtr samplesBufferPtr = IntPtr.Zero;
 		IntPtr autocorTasksPtr = IntPtr.Zero;
-		IntPtr autocorOutputPtr = IntPtr.Zero;
+		IntPtr compLPCOutputPtr = IntPtr.Zero;
 		IntPtr residualTasksPtr = IntPtr.Zero;
 		IntPtr residualOutputPtr = IntPtr.Zero;
 		CUstream cudaStream;
@@ -211,9 +213,10 @@ namespace CUETools.Codecs.FlaCuda
 				cuda.Free(cudaSamples);
 				cuda.Free(cudaAutocorTasks);
 				cuda.Free(cudaAutocorOutput);
+				cuda.Free(cudaCompLPCOutput);
 				cuda.Free(cudaResidualTasks);
 				cuda.Free(cudaResidualOutput);
-				CUDADriver.cuMemFreeHost(autocorOutputPtr);
+				CUDADriver.cuMemFreeHost(compLPCOutputPtr);
 				CUDADriver.cuMemFreeHost(residualOutputPtr);
 				CUDADriver.cuMemFreeHost(samplesBufferPtr);
 				CUDADriver.cuMemFreeHost(residualTasksPtr);
@@ -244,9 +247,10 @@ namespace CUETools.Codecs.FlaCuda
 				cuda.Free(cudaSamples);
 				cuda.Free(cudaAutocorTasks);
 				cuda.Free(cudaAutocorOutput);
+				cuda.Free(cudaCompLPCOutput);
 				cuda.Free(cudaResidualTasks);
 				cuda.Free(cudaResidualOutput);
-				CUDADriver.cuMemFreeHost(autocorOutputPtr);
+				CUDADriver.cuMemFreeHost(compLPCOutputPtr);
 				CUDADriver.cuMemFreeHost(residualOutputPtr);
 				CUDADriver.cuMemFreeHost(samplesBufferPtr);
 				CUDADriver.cuMemFreeHost(residualTasksPtr);
@@ -1031,22 +1035,22 @@ namespace CUETools.Codecs.FlaCuda
 			for (int ch = 0; ch < channelsCount; ch++)
 				for (int iWindow = 0; iWindow < _windowcount; iWindow++)
 				{
-					double* ac = stackalloc double[lpc.MAX_LPC_ORDER + 1];
-					for (int order = 0; order <= max_order; order++)
-					{
-						ac[order] = 0;
-						for (int i_block = 0; i_block < autocorPartCount; i_block++)
-							ac[order] += ((float*)autocorOutputPtr)[order + (max_order + 1) * (i_block + autocorPartCount * (iWindow + _windowcount * ch))];
-					}
-					frame.subframes[ch].lpc_ctx[iWindow].ComputeReflection(max_order, ac);
-					float* lpcs = stackalloc float[lpc.MAX_LPC_ORDER * lpc.MAX_LPC_ORDER];
-					frame.subframes[ch].lpc_ctx[iWindow].ComputeLPC(lpcs);
+					//int* lpcs = ((int*)compLPCOutputPtr) + (max_order + 1) * max_order * (iWindow + _windowcount * ch);
+					//for (int order = 1; order <= max_order; order++)
+					//{
+					//    residualTasks[nResidualTasks].residualOrder = order - 1;
+					//    residualTasks[nResidualTasks].samplesOffs = ch * FlaCudaWriter.MAX_BLOCKSIZE;
+					//    residualTasks[nResidualTasks].shift = lpcs[order + (order - 1) * (max_order + 1)];
+					//    AudioSamples.MemCpy(residualTasks[nResidualTasks].coefs, lpcs + (order - 1) * (max_order + 1), order);
+					//    nResidualTasks++;
+					//}
+					float* lpcs = ((float*)compLPCOutputPtr) + max_order * max_order * (iWindow + _windowcount * ch);
 					for (int order = 1; order <= max_order; order++)
 					{
 						residualTasks[nResidualTasks].residualOrder = order - 1;
 						residualTasks[nResidualTasks].samplesOffs = ch * FlaCudaWriter.MAX_BLOCKSIZE;
 
-						lpc.quantize_lpc_coefs(lpcs + (order - 1) * lpc.MAX_LPC_ORDER,
+						lpc.quantize_lpc_coefs(lpcs + (order - 1) * max_order,
 							order, cbits, residualTasks[nResidualTasks].coefs,
 							out residualTasks[nResidualTasks].shift, 15, 0);
 
@@ -1119,10 +1123,10 @@ namespace CUETools.Codecs.FlaCuda
 		unsafe void compute_autocorellation(FlacFrame frame, int channelsCount, int max_order, out int partCount)
 		{
 			int autocorThreads = 256;
-			int partSize = autocorThreads - max_order;
+			int partSize = 2 * autocorThreads - max_order;
 			int nAutocorTasks = _windowcount * channelsCount;
 
-			partCount = (frame.blocksize + partSize - 1) / partSize;			
+			partCount = (frame.blocksize + partSize - 1) / partSize;
 			if (partCount > maxAutocorParts)
 				throw new Exception("internal error");
 
@@ -1139,10 +1143,19 @@ namespace CUETools.Codecs.FlaCuda
 			cuda.SetParameterSize(cudaComputeAutocor, (uint)(IntPtr.Size * 4) + sizeof(uint) * 3);
 			cuda.SetFunctionBlockShape(cudaComputeAutocor, autocorThreads, 1, 1);
 
+			cuda.SetParameter(cudaComputeLPC, 0, (uint)cudaCompLPCOutput.Pointer);
+			cuda.SetParameter(cudaComputeLPC, IntPtr.Size, (uint)cudaAutocorOutput.Pointer);
+			cuda.SetParameter(cudaComputeLPC, IntPtr.Size * 2, (uint)cudaAutocorTasks.Pointer);
+			cuda.SetParameter(cudaComputeLPC, IntPtr.Size * 3, (uint)max_order);
+			cuda.SetParameter(cudaComputeLPC, IntPtr.Size * 3 + sizeof(uint), (uint)partCount);
+			cuda.SetParameterSize(cudaComputeLPC, (uint)(IntPtr.Size * 3) + sizeof(uint) * 2);
+			cuda.SetFunctionBlockShape(cudaComputeLPC, 32, 1, 1);
+
 			// issue work to the GPU
 			cuda.CopyHostToDeviceAsync(cudaSamples, samplesBufferPtr, (uint)(sizeof(int) * FlaCudaWriter.MAX_BLOCKSIZE * channelsCount), cudaStream);
 			cuda.LaunchAsync(cudaComputeAutocor, partCount, nAutocorTasks, cudaStream);
-			cuda.CopyDeviceToHostAsync(cudaAutocorOutput, autocorOutputPtr, (uint)(sizeof(float) * partCount * (max_order + 1) * nAutocorTasks), cudaStream);
+			cuda.LaunchAsync(cudaComputeLPC, 1, nAutocorTasks, cudaStream);
+			cuda.CopyDeviceToHostAsync(cudaCompLPCOutput, compLPCOutputPtr, (uint)(sizeof(float) * (max_order + 1) * max_order * nAutocorTasks), cudaStream);
 			cuda.SynchronizeStream(cudaStream);
 		}
 		
@@ -1282,18 +1295,20 @@ namespace CUETools.Codecs.FlaCuda
 				cuda.CreateContext(0, CUCtxFlags.SchedSpin);
 				cuda.LoadModule(System.IO.Path.Combine(Environment.CurrentDirectory, "flacuda.cubin"));
 				cudaComputeAutocor = cuda.GetModuleFunction("cudaComputeAutocor");
+				cudaComputeLPC = cuda.GetModuleFunction("cudaComputeLPC");
 				cudaEncodeResidual = cuda.GetModuleFunction("cudaEncodeResidual");
 				cudaSamples = cuda.Allocate((uint)(sizeof(int) * FlaCudaWriter.MAX_BLOCKSIZE * (channels == 2 ? 4 : channels)));
 				cudaWindow = cuda.Allocate((uint)sizeof(float) * FlaCudaWriter.MAX_BLOCKSIZE * 2 * lpc.MAX_LPC_WINDOWS);
 				cudaAutocorTasks = cuda.Allocate((uint)(sizeof(computeAutocorTaskStruct) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS));
 				cudaAutocorOutput = cuda.Allocate((uint)(sizeof(float) * (lpc.MAX_LPC_ORDER + 1) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS) * maxAutocorParts);
+				cudaCompLPCOutput = cuda.Allocate((uint)(sizeof(float) * lpc.MAX_LPC_ORDER * lpc.MAX_LPC_ORDER * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS) * maxAutocorParts);
 				cudaResidualTasks = cuda.Allocate((uint)(sizeof(encodeResidualTaskStruct) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_ORDER * lpc.MAX_LPC_WINDOWS));
 				cudaResidualOutput = cuda.Allocate((uint)(sizeof(int) * (channels == 2 ? 4 : channels) * (lpc.MAX_LPC_ORDER + 1) * lpc.MAX_LPC_WINDOWS * maxResidualParts));
 				CUResult cuErr = CUDADriver.cuMemAllocHost(ref samplesBufferPtr, (uint)(sizeof(int) * (channels == 2 ? 4 : channels) * FlaCudaWriter.MAX_BLOCKSIZE));
 				if (cuErr == CUResult.Success)
 					cuErr = CUDADriver.cuMemAllocHost(ref autocorTasksPtr, (uint)(sizeof(computeAutocorTaskStruct) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS));
 				if (cuErr == CUResult.Success)
-					cuErr = CUDADriver.cuMemAllocHost(ref autocorOutputPtr, (uint)(sizeof(float) * (lpc.MAX_LPC_ORDER + 1) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS * maxAutocorParts));
+					cuErr = CUDADriver.cuMemAllocHost(ref compLPCOutputPtr, (uint)(sizeof(float) * (lpc.MAX_LPC_ORDER + 1) * lpc.MAX_LPC_ORDER * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS));
 				if (cuErr == CUResult.Success)
 					cuErr = CUDADriver.cuMemAllocHost(ref residualTasksPtr, (uint)(sizeof(encodeResidualTaskStruct) * (channels == 2 ? 4 : channels) * lpc.MAX_LPC_WINDOWS * lpc.MAX_LPC_ORDER));
 				if (cuErr == CUResult.Success)
@@ -1302,7 +1317,7 @@ namespace CUETools.Codecs.FlaCuda
 				{
 					if (samplesBufferPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(samplesBufferPtr); samplesBufferPtr = IntPtr.Zero;
 					if (autocorTasksPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(autocorTasksPtr); autocorTasksPtr = IntPtr.Zero;
-					if (autocorOutputPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(autocorOutputPtr); autocorOutputPtr = IntPtr.Zero;
+					if (compLPCOutputPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(compLPCOutputPtr); compLPCOutputPtr = IntPtr.Zero;
 					if (residualTasksPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(residualTasksPtr); residualTasksPtr = IntPtr.Zero;
 					if (residualOutputPtr != IntPtr.Zero) CUDADriver.cuMemFreeHost(residualOutputPtr); residualOutputPtr = IntPtr.Zero;
 					throw new CUDAException(cuErr);
diff --git a/CUETools.FlaCuda/flacuda.cu b/CUETools.FlaCuda/flacuda.cu
index 22c3134..9d224df 100644
--- a/CUETools.FlaCuda/flacuda.cu
+++ b/CUETools.FlaCuda/flacuda.cu
@@ -33,17 +33,17 @@ extern "C" __global__ void cudaComputeAutocor(
     computeAutocorTaskStruct *tasks,
     int max_order, // should be <= 32
     int frameSize,
-    int partSize // should be <= blockDim - max_order
+    int partSize // should be <= 2*blockDim - max_order
 )
 {
     __shared__ struct {
-	float data[256];
+	float data[512];
 	float product[256];
-	float product2[256];
 	float sum[33];
 	computeAutocorTaskStruct task;
     } shared;
     const int tid = threadIdx.x;
+    const int tid2 = threadIdx.x + 256;
     // fetch task data
     if (tid < sizeof(shared.task) / sizeof(int))
 	((int*)&shared.task)[tid] = ((int*)(tasks + blockIdx.y))[tid];
@@ -55,11 +55,13 @@ extern "C" __global__ void cudaComputeAutocor(
 
     // fetch samples
     shared.data[tid] = tid < dataLen ? samples[shared.task.samplesOffs + pos + tid] * window[shared.task.windowOffs + pos + tid]: 0.0f;
+    shared.data[tid2] = tid2 < dataLen ? samples[shared.task.samplesOffs + pos + tid2] * window[shared.task.windowOffs + pos + tid2]: 0.0f;
     __syncthreads();
 
     for (int lag = 0; lag <= max_order; lag++)
     {
-	shared.product[tid] = tid < productLen ? shared.data[tid] * shared.data[tid + lag] : 0.0f;
+	shared.product[tid] = (tid < productLen) * shared.data[tid] * shared.data[tid + lag] +
+	    + (tid2 < productLen) * shared.data[tid2] * shared.data[tid2 + lag];
 	__syncthreads();
 
 	// product sum: reduction in shared mem
@@ -72,6 +74,7 @@ extern "C" __global__ void cudaComputeAutocor(
 	shared.product[tid] += shared.product[tid + 4];
 	shared.product[tid] += shared.product[tid + 2];
 	if (tid == 0) shared.sum[lag] = shared.product[0] + shared.product[1];
+	__syncthreads();
     }
 
     // return results
@@ -79,6 +82,86 @@ extern "C" __global__ void cudaComputeAutocor(
 	output[(blockIdx.x + blockIdx.y * gridDim.x) * (max_order + 1) + tid] = shared.sum[tid];
 }
 
+extern "C" __global__ void cudaComputeLPC(
+    float*output,
+    float*autoc,
+    computeAutocorTaskStruct *tasks,
+    int max_order, // should be <= 32
+    int partCount // should be <= blockDim
+)
+{
+    __shared__ struct {
+	computeAutocorTaskStruct task;
+	float tmp[32];
+	float buf[32];
+	int   bits[32];
+	float autoc[33];
+    } shared;
+    const int tid = threadIdx.x;
+    
+    // fetch task data
+    if (tid < sizeof(shared.task) / sizeof(int))
+	((int*)&shared.task)[tid] = ((int*)(tasks + blockIdx.y))[tid];
+    
+    // initialize autoc sums
+    if (tid <= max_order) 
+	shared.autoc[tid] = 0.0f;
+    
+    __syncthreads();
+
+    // add up parts
+    for (int part = 0; part < partCount; part++)
+	if (tid <= max_order) 
+	    shared.autoc[tid] += autoc[(blockIdx.y * partCount + part) * (max_order + 1) + tid];
+    
+    __syncthreads();
+
+    if (tid <= 32)
+	shared.tmp[tid] = 0.0f;
+
+    float err = shared.autoc[0];
+
+    for(int order = 0; order < max_order; order++)
+    {
+	if (tid < 32) 
+	{
+	    shared.buf[tid] = tid < order ? shared.tmp[tid] * shared.autoc[order - tid] : 0;
+	    shared.buf[tid] += shared.buf[tid + 16];
+	    shared.buf[tid] += shared.buf[tid + 8];
+	    shared.buf[tid] += shared.buf[tid + 4];
+	    shared.buf[tid] += shared.buf[tid + 2];
+	    shared.buf[tid] += shared.buf[tid + 1];
+	}
+	__syncthreads();
+        
+	float r = (- shared.autoc[order+1] - shared.buf[0]) / err;
+        
+	err *= 1.0f - (r * r);
+        
+	if (tid == 0)
+	    shared.tmp[order] = r; // we could also set shared.tmp[-1] to 1.0f
+	if (tid < order)
+	    shared.tmp[tid] += r * shared.tmp[order - 1 - tid];
+	if (tid <= order)
+	    output[((blockIdx.x + blockIdx.y * gridDim.x) * max_order + order) * max_order + tid] = -shared.tmp[tid];
+	//{
+	//    int precision = 13;
+	//    shared.bits[tid] = 32 - __clz(__float2int_rn(fabs(shared.tmp[tid]) * (1 << 15))) - precision;
+	//    shared.bits[tid] = max(shared.bits[tid], shared.bits[tid + 16]);
+	//    shared.bits[tid] = max(shared.bits[tid], shared.bits[tid + 8]);
+	//    shared.bits[tid] = max(shared.bits[tid], shared.bits[tid + 4]);
+	//    shared.bits[tid] = max(shared.bits[tid], shared.bits[tid + 2]);
+	//    shared.bits[tid] = max(shared.bits[tid], shared.bits[tid + 1]);
+	//    int sh = max(0,min(15, 15 - shared.bits[0]));
+	//    shared.bits[tid] = max(-(1 << precision),min((1 << precision)-1,__float2int_rn(-shared.tmp[tid] * (1 << sh))));
+	//    if (tid == 0)
+	//	output[((blockIdx.x + blockIdx.y * gridDim.x) * max_order + order) * (1 + max_order) + order + 1] = sh;
+	//    output[((blockIdx.x + blockIdx.y * gridDim.x) * max_order + order) * (1 + max_order) + tid] = shared.bits[tid];
+	//}
+	__syncthreads();
+    }
+}
+
 typedef struct
 {
     int residualOrder; // <= 32
@@ -108,19 +191,22 @@ extern "C" __global__ void cudaEncodeResidual(
 	((int*)&shared.task)[tid] = ((int*)(tasks + blockIdx.y))[tid];
     __syncthreads();
     const int pos = blockIdx.x * partSize;
-    const int residualOrder = shared.task.residualOrder;
-    const int residualLen = min(frameSize - pos - residualOrder - 1, partSize);
-    const int dataLen = residualLen + residualOrder + 1;
+    const int residualOrder = shared.task.residualOrder + 1;
+    const int residualLen = min(frameSize - pos - residualOrder, partSize);
+    const int dataLen = residualLen + residualOrder;
 
     // fetch samples
     shared.data[tid] = (tid < dataLen ? samples[shared.task.samplesOffs + pos + tid] : 0);
+
+    // reverse coefs
+    if (tid < residualOrder) shared.task.coefs[tid] = shared.task.coefs[residualOrder - 1 - tid];
     
     // compute residual
     __syncthreads();
     long sum = 0;
-    for (int c = 0; c <= residualOrder; c++)
-	sum += __mul24(shared.data[tid + c], shared.task.coefs[residualOrder - c]);
-    int res = shared.data[tid + residualOrder + 1] - (sum >> shared.task.shift);
+    for (int c = 0; c < residualOrder; c++)
+	sum += __mul24(shared.data[tid + c], shared.task.coefs[c]);
+    int res = shared.data[tid + residualOrder] - (sum >> shared.task.shift);
     shared.residual[tid] = __mul24(tid < residualLen, (2 * res) ^ (res >> 31));
     
     __syncthreads();