/// <summary>
/// Attempt to preallocate the circular buffer for as many images as possible that fits in available memory.
/// </summary>
public bool AllocateBuffers(ImageDescriptor imageDescriptor, long availableMemory)
{
if (!NeedsReallocation(imageDescriptor, availableMemory))
{
return(true);
}
int targetCapacity = (int)(availableMemory / imageDescriptor.BufferSize);
bool memoryPressure = minCapacity * imageDescriptor.BufferSize > availableMemory;
if (memoryPressure)
{
// The user explicitly asked to not use enough memory. We try to honor the request by lowering the min levels.
// This may result in thread cross talks.
reserveCapacity = Math.Max(targetCapacity, 2);
minCapacity = Math.Max(targetCapacity + 1, 3);
targetCapacity = Math.Max(targetCapacity, minCapacity);
}
else
{
reserveCapacity = 8;
minCapacity = 12;
targetCapacity = Math.Max(targetCapacity, minCapacity);
}
bool compatible = ImageDescriptor.Compatible(this.imageDescriptor, imageDescriptor);
if (compatible && targetCapacity <= fullCapacity)
{
FreeSome(targetCapacity);
this.fullCapacity = frames.Count;
this.availableMemory = availableMemory;
return(true);
}
if (!compatible)
{
FreeAll();
}
stopwatch.Restart();
frames.Capacity = targetCapacity;
log.DebugFormat("Allocating {0} frames.", targetCapacity - fullCapacity);
int bufferSize = ImageFormatHelper.ComputeBufferSize(imageDescriptor.Width, imageDescriptor.Height, imageDescriptor.Format);
try
{
for (int i = fullCapacity; i < targetCapacity; i++)
{
Frame slot = new Frame(bufferSize);
frames.Add(slot);
}
}
catch (Exception e)
{
log.ErrorFormat("Error while allocating delay buffer.");
log.Error(e);
}
if (frames.Count > 0)
{
// The following variables are used during frame -> bitmap conversion.
this.rect = new Rectangle(0, 0, imageDescriptor.Width, imageDescriptor.Height);
this.pitch = imageDescriptor.Width * 3;
this.tempJpeg = new byte[bufferSize];
this.allocated = true;
this.fullCapacity = frames.Count;
this.availableMemory = availableMemory;
this.imageDescriptor = imageDescriptor;
// Better do the GC now to push everything to gen2 and LOH rather than taking a hit later during normal streaming operations.
GC.Collect(2);
}
log.DebugFormat("Allocated delay buffer: {0} ms. Total: {1} frames.", stopwatch.ElapsedMilliseconds, fullCapacity);
return(allocated);
}
/// <summary>
/// Returns true if the delayer needs to allocate or reallocate memory.
/// </summary>
public bool NeedsReallocation(ImageDescriptor imageDescriptor, long availableMemory)
{
return(!allocated || !ImageDescriptor.Compatible(this.imageDescriptor, imageDescriptor) || this.availableMemory != availableMemory);
}