CMediaSample Class

The CMediaSample class defines a media sample that supports the IMediaSample2 interface. The media sample contains a pointer to a memory buffer, and various properties stored as protected member variables.

Media samples are created by allocators, which are derived from the CBaseAllocator class. The CMediaSample constructor receives a pointer to an allocated buffer, along with the size of the buffer. Other properties are typically set and retrieved through IMediaSample interface methods.

The life cycle of a media sample differs from that of most COM objects:

• The allocator holds a list of free samples. When a filter needs a new sample, it calls the allocator's IMemAllocator::GetBuffer method. The allocator retrieves a sample from its free list, increments the sample's reference count, and returns a pointer to the sample.
• After the filter is done with the sample, it calls the IUnknown::Release method on the sample. Unlike most objects, the sample does not delete itself when its reference count reaches zero. Instead, it calls the IMemAllocator::ReleaseBuffer method on the allocator, and the allocator returns the sample to its free list.
• The allocator does not destroy samples until the IMemAllocator::Decommit method is called.

Requirements

Header: Declared in Amfilter.h; include Streams.h.

Library: Use Strmbase.lib (retail builds) or Strmbasd.lib (debug builds).