Creates a sink buffer for the specified media ID. The default version returns NULL.

The CMMFBuffer sink buffer.

Creates a source buffer.

This is a virtual function that each derived class must implement.

This function should create a buffer of length 0, the maximum length should be equal to the maximum possible frame size. In the case of non framed data it should be set to an arbitrary size, which is effectively a trade off between being too small which will affect performance as more source reads are required, and being too large which will give very coarse positioning granularity. For pcm data, a buffer size of 4K is a good compromise. The same compromise also applies when deciding to put multiple audio frames into one format frame. The sink buffer size may also effect the format buffer size and the controller may use this to suggest a buffer size to the format by calling the format's SuggestSourceBufferSize() method. Alternatively the MDataSource::CreateSourceBufferL() function that takes the additional aSinkBuffer parameter may also be used when deciding the source buffer maximum size of the created source buffer.

The created source buffer.

Returns the duration of the clip for the specified media type.

This is a virtual function that each derived class must implement.

The duration of the clip.

Adds a buffer to a clip.

Request from CMMFDataPath to fill the specified buffer. The CMMFFormat needs to break this down into one or more reads from the clip (from MDataSource - CMMFFormatDecode is a MDataSource to a CMMFDataPath consumer).

This is a virtual function that each derived class must implement.

This method is the means by which data is obtained from the data source. aBuffer is the buffer that needs filling from the source data stream as identified by aMediaId. The format should read the frame number of the buffer via the buffer's CMMFBuffer::FrameNumber() method. From this the format should be able to determine the actual position of the data on the data source. The technique here depends on the nature of the format. For a linear audio format, the position can be obtained by a simple calculation of the frame size, the header size and where appropriate the datatype.

For non-linear formats either an index table of frame number and location will need to be created in the NewL() or some form of approximating algorithm will be required. Some formats have an index table as part of the format e.g. AVI. If no random access is required then no index table is required, the format can keep track of the current read position and increment it on each access, and reset it if the frame number is reset to 0 or 1. Given that for non-linear i.e. variable bit rate formats, the size of the data read may vary from frame to frame, then the format should either set the request size of the buffer for the required frame or call the source's ReadBufferL() (either CMMFClip::ReadBufferL(), CMMFDescriptor ReadBufferL() or CMMFFile::ReadBufferL()) function that takes the aLength parameter.

It is the responsibility of the format decode to determine the size and position of the source data for each frame. For linear audio formats, the format decode should fill the buffer up to its maximum length. For multimedia formats e.g. mp4, AVI etc, the format decode is effectively acting as a demultiplexor, and must obtain the appropriate data from the source depending on the aMediaId.

Returns the time interval for one frame for the specified media type.

This is a virtual function that each derived class must implement.

In the case of video, a frame would usually be one frame of video. In the case of audio, a frame may correspond to a frame of audio, if the particular audio data type is framed eg mp3. There are two definitions of a frame. A format frame, which may consist of several frames of a particular framed audio data type. This may be the case, for example for GSM610 (a low quality audio data type used in telephony) where a frame is only 65 bytes large. In this case a format frame consists of several GSM610 data type frames as passing the data out 65 bytes at a time would be inefficient. In the case of non-framed data such as pcm, a frame can be an arbitrary size determined by the format plugin.

The frame time interval

Gets the number of meta data entries.

Meta Data support. The decode format is only capable of reading meta data entries from the clip.

This is an optional method, used to return the number of meta data entries present in the format. A meta data entry is a format-specific field such as authorship, copyright, security details etc. The function is optional as many formats do not provide support for such additional meta data fields.

The default leaves with KErrNotSupported.

Gets the supported bit rates.

The default leaves with KErrNotSupported.

This should return an array of bit rates supported by the format where applicable. Note that this refers to the possible bit rates supported by the format, not the actual bit rate, which will be one of the supported bit rates. The implementation of this function is optional.

Gets the supported data types for the given media type id.

The default leaves with KErrNotSupported.

The implementation of this procedure should return an array of data types supported by the format where applicable. Note that this refers to the possible data types that may be supported by the format, not the actual data type of the format, which will be one of the supported data types. For example, for a format decode plugin capable of supporting pcm16 and GSM610 the procedure would return an array of length two the first array member containing the fourCC code ' P16' and the second containing the value GSM6. The implementation of this function is optional.

Gets the supported number of channels.

The default leaves with KErrNotSupported.

The implementation of this procedure should return an array of channels supported by the format where applicable. Note that this refers to the possible number of channels supported by the format, not the actual number of channels, which will be one of the supported channels. For example, for a format decode plugin capable of supporting mono and stereo the procedure would return an array of length two the first array member containing the value 1 and the second containing the value 2. The implementation of this function is optional.

Gets the supported sample rates.

The default implementation leaves with KErrNotSupported.

This should return an array of sample rates supported by the format where applicable. Note that this refers to the possible sample rates supported by the format, not the actual sample rate, which will be one of the supported sample rates. The implementation of this function is optional.

Returns the ECom plugin UID of this format.

The plugin UID.

Returns the specified meta data entry.

This method is optional as many formats do not provide support for such additional meta data fields.

The default leaves with KErrNotSupported.

The meta data entry.