CMMFFormatDecode Class Reference

class CMMFFormatDecode : public CBase

Base class from which source formats can be derived from. The intended usage is for controllers that can support more than one type of format. The class is an MDataSource as far as the data path is concerned but is an MDataSink to the clip that is the source of the actual data.

All CMMFFormatDecode plugin DLLs must include interface_uid = KMmfUidPluginInterfaceFormatDecode in their .rss files.

Inherits from

Public Member Functions
~CMMFFormatDecode()
TUint BitRate()
voidBufferEmptiedL(CMMFBuffer *)
voidBufferFilledL(CMMFBuffer *)
TBool CanCreateSinkBuffer()
TBool CanCreateSourceBuffer()
CMMFBuffer *CreateSinkBufferL(TMediaId, TBool &)
CMMFBuffer *CreateSourceBufferL(TMediaId, TBool &)
TTimeIntervalMicroSeconds Duration(TMediaId)
voidEmptyBufferL(CMMFBuffer *, MDataSource *, TMediaId)
voidFillBufferL(CMMFBuffer *, MDataSink *, TMediaId)
TTimeIntervalMicroSeconds FrameTimeInterval(TMediaId)
voidGetNumberOfMetaDataEntriesL(TInt &)
voidGetSupportedBitRatesL(RArray< TUint > &)
voidGetSupportedDataTypesL(TMediaId, RArray< TFourCC > &)
voidGetSupportedNumChannelsL(RArray< TUint > &)
voidGetSupportedSampleRatesL(RArray< TUint > &)
TUid ImplementationUid()
CMMFMetaDataEntry *MetaDataEntryL(TInt)
IMPORT_C CMMFFormatDecode *NewL(TUid, MDataSource *)
IMPORT_C CMMFFormatDecode *NewL(const TDesC &, MDataSource *, const TDesC &)
IMPORT_C CMMFFormatDecode *NewL(const TDesC8 &, MDataSource *, const TDesC &)
IMPORT_C CMMFFormatDecode *NewL(MDataSource *, const TDesC &)
IMPORT_C CMMFFormatDecode *NewL(const TDesC &, MDataSource *, const TDesC &, TBool &)
IMPORT_C CMMFFormatDecode *NewL(const TDesC8 &, MDataSource *, const TDesC &, TBool &)
IMPORT_C CMMFFormatDecode *NewL(MDataSource *, const TDesC &, TBool &)
TUint NumChannels()
TTimeIntervalMicroSeconds PositionL()
TUint SampleRate()
TInt SetBitRate(TUint)
TInt SetNumChannels(TUint)
voidSetPositionL(const TTimeIntervalMicroSeconds &)
TInt SetSampleRate(TUint)
TFourCC SinkDataTypeCode(TMediaId)
TFourCC SourceDataTypeCode(TMediaId)
TUint Streams(TUid)
voidSuggestSourceBufferSize(TUint)
Protected Member Functions
CMMFFormatDecode()
voidConstructSinkL(const TDesC8 &)
voidConstructSourceL(const TDesC8 &)
CMMFFormatDecode *CreateFormatL(TUid, MDataSource *)
Inherited Functions
CBase::CBase()
CBase::Delete(CBase *)
CBase::Extension_(TUint,TAny *&,TAny *)
CBase::operator new(TUint)
CBase::operator new(TUint,TAny *)
CBase::operator new(TUint,TLeave)
CBase::operator new(TUint,TLeave,TUint)
CBase::operator new(TUint,TUint)
CBase::~CBase()
Protected Attributes
MDataSource *iClip
MDataSink *iDataPath
Private Attributes
TUid iDtor_ID_Key
TUid iImplementationUid

Constructor & Destructor Documentation

CMMFFormatDecode()

CMMFFormatDecode()[protected, inline]

Default constructor

~CMMFFormatDecode()

~CMMFFormatDecode()[inline, virtual]

Destructor.

Member Functions Documentation

BitRate()

TUint BitRate()[inline, virtual]

Gets the bit rate.

The default implementation returns 0.

This method is mainly provided for variable bit rate formats, such as mp3, where the bit rate can not be directly calculated from the sample rate. This function needs overriding for any format decode that supports audio.

The bit rate.

BufferEmptiedL(CMMFBuffer *)

voidBufferEmptiedL(CMMFBuffer *aBuffer)[inline, virtual]

Indicates data has been added to the file.

Parameters

CMMFBuffer * aBufferThe emptied buffer.

BufferFilledL(CMMFBuffer *)

voidBufferFilledL(CMMFBuffer *aBuffer)[inline, virtual]

Indicates the data source has filled the buffer.

Called by the CMMFFormat's MDataSource when it has filled the buffer. The default implementation below would need overriding in cases where multiple clip reads were required to fill the buffer from the data path.

Parameters

CMMFBuffer * aBufferThe buffer to which the clip is added.

CanCreateSinkBuffer()

TBool CanCreateSinkBuffer()[inline, virtual]

Tests whether a sink buffer can be created.

Format would normally pass its own buffer onto the CMMFClip, so this may not be required. The default returns EFalse.

A boolean indicating if the sink buffer can be created. ETrue if buffer can be created, EFalse otherwise.

CanCreateSourceBuffer()

TBool CanCreateSourceBuffer()[inline, virtual]

Tests whether a source buffer can be created.

The format knows what type of source buffer it requires so default returns ETrue. It doesn't usually need to set the size of this buffer.

A boolean indicating whether a buffer can be created. ETrue if the buffer can be created, EFalse otherwise.

ConstructSinkL(const TDesC8 &)

voidConstructSinkL(const TDesC8 &)[protected, inline, virtual]

Parameters

const TDesC8 &

ConstructSourceL(const TDesC8 &)

voidConstructSourceL(const TDesC8 &)[protected, inline, virtual]

Parameters

const TDesC8 &

CreateFormatL(TUid, MDataSource *)

CMMFFormatDecode *CreateFormatL(TUidaImplementationUid,
MDataSource *aSource
)[protected, static]

Parameters

TUid aImplementationUid
MDataSource * aSource

CreateSinkBufferL(TMediaId, TBool &)

CMMFBuffer *CreateSinkBufferL(TMediaIdaMediaId,
TBool &aReference
)[inline, virtual]

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

The CMMFBuffer sink buffer.

Parameters

TMediaId aMediaIdThe media type ID.
TBool & aReferenceIf ETrue the MDataSink owns the buffer. If EFalse, then the caller owns the buffer.

CreateSourceBufferL(TMediaId, TBool &)

CMMFBuffer *CreateSourceBufferL(TMediaIdaMediaId,
TBool &aReference
)[pure virtual]

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.

Parameters

TMediaId aMediaIdThe media type ID.
TBool & aReferenceIf ETrue the MDataSource owns the buffer. If EFalse, then the caller owns the buffer. This should normally be set to EFalse as format plugins do not create the reference buffer.

Duration(TMediaId)

TTimeIntervalMicroSeconds Duration(TMediaIdaMediaType)const [pure virtual]

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.

Parameters

TMediaId aMediaTypeThe media type ID.

EmptyBufferL(CMMFBuffer *, MDataSource *, TMediaId)

voidEmptyBufferL(CMMFBuffer *aBuffer,
MDataSource *aSupplier,
TMediaIdaMediaId
)[inline, virtual]

Adds a buffer to a clip.

Parameters

CMMFBuffer * aBufferThe buffer to which the clip is added.
MDataSource * aSupplierThe data source.
TMediaId aMediaIdThe Media ID.

FillBufferL(CMMFBuffer *, MDataSink *, TMediaId)

voidFillBufferL(CMMFBuffer *aBuffer,
MDataSink *aConsumer,
TMediaIdaMediaId
)[pure virtual]

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.

Parameters

CMMFBuffer * aBufferThe buffer to fill.
MDataSink * aConsumerThe consumer.
TMediaId aMediaIdThe media type ID.

FrameTimeInterval(TMediaId)

TTimeIntervalMicroSeconds FrameTimeInterval(TMediaIdaMediaType)const [pure virtual]

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

Parameters

TMediaId aMediaTypeThe media type id.

GetNumberOfMetaDataEntriesL(TInt &)

voidGetNumberOfMetaDataEntriesL(TInt &aNumberOfEntries)[inline, virtual]

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.

Parameters

TInt & aNumberOfEntriesA reference to the number of meta data entries supported by the format. On return, contains the number of meta data entries.

GetSupportedBitRatesL(RArray< TUint > &)

voidGetSupportedBitRatesL(RArray< TUint > &aBitRates)[inline, virtual]

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.

Parameters

RArray< TUint > & aBitRatesReference to an array of supported bit rates.

GetSupportedDataTypesL(TMediaId, RArray< TFourCC > &)

voidGetSupportedDataTypesL(TMediaIdaMediaId,
RArray< TFourCC > &aDataTypes
)[inline, virtual]

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.

Parameters

TMediaId aMediaIdThe media type id.
RArray< TFourCC > & aDataTypesA reference to an array of supported data types.

GetSupportedNumChannelsL(RArray< TUint > &)

voidGetSupportedNumChannelsL(RArray< TUint > &aNumChannels)[inline, virtual]

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.

Parameters

RArray< TUint > & aNumChannelsA reference to an array of supported number of channels.

GetSupportedSampleRatesL(RArray< TUint > &)

voidGetSupportedSampleRatesL(RArray< TUint > &aSampleRates)[inline, virtual]

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.

Parameters

RArray< TUint > & aSampleRatesReference to an array of supported sample rates.

ImplementationUid()

TUid ImplementationUid()const [inline]

Returns the ECom plugin UID of this format.

The plugin UID.

MetaDataEntryL(TInt)

CMMFMetaDataEntry *MetaDataEntryL(TIntaIndex)[inline, virtual]

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.

Parameters

TInt aIndexThe zero based meta data entry index to retrieve.

NewL(TUid, MDataSource *)

IMPORT_C CMMFFormatDecode *NewL(TUidaUid,
MDataSource *aSource
)[static]

Parameters

TUid aUid
MDataSource * aSource

NewL(const TDesC &, MDataSource *, const TDesC &)

IMPORT_C CMMFFormatDecode *NewL(const TDesC &aFileName,
MDataSource *aSource,
const TDesC &aPreferredSupplier
)[static]

Parameters

const TDesC & aFileName
MDataSource * aSource
const TDesC & aPreferredSupplier

NewL(const TDesC8 &, MDataSource *, const TDesC &)

IMPORT_C CMMFFormatDecode *NewL(const TDesC8 &aSourceHeader,
MDataSource *aSource,
const TDesC &aPreferredSupplier
)[static]

Parameters

const TDesC8 & aSourceHeader
MDataSource * aSource
const TDesC & aPreferredSupplier

NewL(MDataSource *, const TDesC &)

IMPORT_C CMMFFormatDecode *NewL(MDataSource *aSource,
const TDesC &aPreferredSupplier
)[static]

Parameters

MDataSource * aSource
const TDesC & aPreferredSupplier

NewL(const TDesC &, MDataSource *, const TDesC &, TBool &)

IMPORT_C CMMFFormatDecode *NewL(const TDesC &aFileName,
MDataSource *aSource,
const TDesC &aPreferredSupplier,
TBool &aSupportsCustomInterfaces
)[static]

Parameters

const TDesC & aFileName
MDataSource * aSource
const TDesC & aPreferredSupplier
TBool & aSupportsCustomInterfaces

NewL(const TDesC8 &, MDataSource *, const TDesC &, TBool &)

IMPORT_C CMMFFormatDecode *NewL(const TDesC8 &aSourceHeader,
MDataSource *aSource,
const TDesC &aPreferredSupplier,
TBool &aSupportsCustomInterfaces
)[static]

Parameters

const TDesC8 & aSourceHeader
MDataSource * aSource
const TDesC & aPreferredSupplier
TBool & aSupportsCustomInterfaces

NewL(MDataSource *, const TDesC &, TBool &)

IMPORT_C CMMFFormatDecode *NewL(MDataSource *aSource,
const TDesC &aPreferredSupplier,
TBool &aSupportsCustomInterfaces
)[static]

Parameters

MDataSource * aSource
const TDesC & aPreferredSupplier
TBool & aSupportsCustomInterfaces

NumChannels()

TUint NumChannels()[inline, virtual]

Returns the number of channels.

The default implementation returns 0.

The number of channels.

PositionL()

TTimeIntervalMicroSeconds PositionL()[inline, virtual]

Supplies the current position.

Subsequent data reads will commence from this position.

The current position in microseconds.

SampleRate()

TUint SampleRate()[inline, virtual]

Gets the sample rate.

The default implementation returns 0.

The sample rate.

SetBitRate(TUint)

TInt SetBitRate(TUintaBitRate)[inline, virtual]

Sets the bit rate.

The default implementation returns KErrNotSupported.

This method is mainly provided for variable bit rate formats, such as mp3, where the bit rate can not be directly calculated from the sample rate. There would normally be no need to override this function as the format decode can normally determine the sample rate for itself. It is only necessary to override this in cases where the format decode plugin cannot determine for itself the sample rate.

An error code indicating if the function call was successful. KErrNone on success, otherwise another of the system-wide error codes.

Parameters

TUint aBitRateThe bit rate in bits per second.

SetNumChannels(TUint)

TInt SetNumChannels(TUintaChannels)[inline, virtual]

Sets the number of channels.

The default returns KErrNotSupported.

There would normally be no need to override this function as the format decode plugin can normally determine for itself the number of channels. It is only necessary to override this in cases where the format decode plugin cannot determine for itself the number of channels. This function should not be used if the audio clip already exists; that is, in the "Open and Append" scenario, when the function's behaviour is undefined.

An error code indicating if the function call was successful. KErrNone on success, otherwise another of the system-wide error codes.

Parameters

TUint aChannelsThe number of channels.

SetPositionL(const TTimeIntervalMicroSeconds &)

voidSetPositionL(const TTimeIntervalMicroSeconds &aPosition)[inline, virtual]

Used to set the format's position.

Subsequent data reads should ignore the FrameNumber in the CMMFBuffer and use this setting to determine what data to provide.

The actual position the format sets itself may vary from this setting to ensure that it is aligned to the sample boundaries ensuring consistent data output.

If not supported, positional information should be extracted from the FrameNumber in CMMFBuffer

Parameters

const TTimeIntervalMicroSeconds & aPositionThe position the format should use.

SetSampleRate(TUint)

TInt SetSampleRate(TUintaSampleRate)[inline, virtual]

Sets the sample rate.

The default implementation returns KErrNotSupported.

There would normally be no need to override this function as the format decode can normally determine the sample rate for itself. It is only necessary to override this in cases where the format decode plugin cannot determine for itself the sample rate.

An error code indicating if the function call was successful. KErrNone on success, otherwise another of the system-wide error codes.

Parameters

TUint aSampleRateThe sample rate.

SinkDataTypeCode(TMediaId)

TFourCC SinkDataTypeCode(TMediaIdaMediaId)[inline, virtual]

Returns the sink data type code for the specified media type ID. This would be the same as the source data type four CC although the clip is not going to need this info.

The sink data type code.

Parameters

TMediaId aMediaIdThe media type id.

SourceDataTypeCode(TMediaId)

TFourCC SourceDataTypeCode(TMediaIdaMediaId)[pure virtual]

Returns the source data type code for the specified media type ID.

Used by the CMMFDataPath for codec matching.

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

The source data type code.

Parameters

TMediaId aMediaIdThe media type ID.

Streams(TUid)

TUint Streams(TUidaMediaType)const [pure virtual]

Gets the number of streams of the specified media type.

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

The number of streams of multimedia data in the format for the specified media type. For example, for a WAV or mp3 audio file this procedure would return 1 for a media type of audio and 0 for a media type of video. More complex multimedia formats (for example AVI and mp4) can support multiple streams of both video and audio.

Parameters

TUid aMediaTypeThe UID of the media type, for example KUidMediaTypeAudio or KUidMediaTypeVideo.

SuggestSourceBufferSize(TUint)

voidSuggestSourceBufferSize(TUintaSuggestedBufferSize)[inline, virtual]

Used by the sink to suggest a source buffer size.

This is an optional function provided so that a controller can suggest a buffer size for the format. The controller should not assume that the format will accept the suggested buffer size and there is no obligation on behalf of the format to use the suggested buffer size.

Parameters

TUint aSuggestedBufferSizeA recommended buffer size that the format should create.

Member Data Documentation

MDataSource * iClip

MDataSource *iClip[protected]

The clip is the source for the decode format.

MDataSink * iDataPath

MDataSink *iDataPath[protected]

The data path is the sink for the decode format.

TUid iDtor_ID_Key

TUid iDtor_ID_Key[private]

TUid iImplementationUid

TUid iImplementationUid[private]