OpalTranscoder Class Reference

#include <transcoders.h>

Inheritance diagram for OpalTranscoder:


Operations
virtual bool	UpdateMediaFormats (const OpalMediaFormat &inputMediaFormat, const OpalMediaFormat &outputMediaFormat)
virtual PBoolean	ExecuteCommand (const OpalMediaCommand &command)
virtual PINDEX	GetOptimalDataFrameSize (PBoolean input) const=0
virtual PBoolean	ConvertFrames (const RTP_DataFrame &input, RTP_DataFrameList &output)
virtual PBoolean	Convert (const RTP_DataFrame &input, RTP_DataFrame &output)=0
static OpalTranscoder *	Create (const OpalMediaFormat &srcFormat, const OpalMediaFormat &dstFormat, const BYTE *instance=NULL, unsigned instanceLen=0)
static bool	SelectFormats (const OpalMediaFormatList &srcFormats, const OpalMediaFormatList &dstFormats, const OpalMediaFormatList &allFormats, OpalMediaFormat &srcFormat, OpalMediaFormat &dstFormat)
static bool	FindIntermediateFormat (const OpalMediaFormat &srcFormat, const OpalMediaFormat &dstFormat, OpalMediaFormat &intermediateFormat)
static OpalMediaFormatList	GetDestinationFormats (const OpalMediaFormat &srcFormat)
static OpalMediaFormatList	GetSourceFormats (const OpalMediaFormat &dstFormat)
static OpalMediaFormatList	GetPossibleFormats (const OpalMediaFormatList &formats)
Public Member Functions
Operations
PINDEX	GetMaxOutputSize () const
void	SetMaxOutputSize (PINDEX size)
void	SetCommandNotifier (const PNotifier &notifier)
const PNotifier &	GetCommandNotifier () const
virtual void	SetInstanceID (const BYTE *instance, unsigned instanceLen)
RTP_DataFrame::PayloadTypes	GetPayloadType (PBoolean input) const
virtual bool	AcceptComfortNoise () const
virtual bool	AcceptEmptyPayload () const
virtual bool	AcceptOtherPayloads () const
Protected Attributes
PINDEX	maxOutputSize
PNotifier	commandNotifier
PMutex	updateMutex
PBoolean	outputIsRTP
PBoolean	inputIsRTP
bool	acceptEmptyPayload
bool	acceptOtherPayloads

Detailed Description

This class embodies the implementation of a specific transcoder instance used to convert data from one format to another.

An application may create a descendent off this class and override functions as required for implementing a transcoder.

Constructor & Destructor Documentation

OpalTranscoder::OpalTranscoder	(	const OpalMediaFormat &	inputMediaFormat,
		const OpalMediaFormat &	outputMediaFormat
	)

Create a new transcoder implementation.

Parameters:

inputMediaFormat	Input media format
outputMediaFormat	Output media format

OpalTranscoder::OpalTranscoder	(	const OpalMediaFormat &	inputMediaFormat,
		const OpalMediaFormat &	outputMediaFormat
	)

Create a new transcoder implementation.

Parameters:

inputMediaFormat	Input media format
outputMediaFormat	Output media format

Member Function Documentation

virtual bool OpalTranscoder::UpdateMediaFormats	(	const OpalMediaFormat &	inputMediaFormat,
		const OpalMediaFormat &	outputMediaFormat
	)			`[virtual]`

Update the input and output media formats. This can be used to adjust the parameters of a codec at run time. Note you cannot change the basic media format, eg change GSM0610 to G.711, only options for that format, eg 6k3 mode to 5k3 mode in G.723.1. If the formats are different then a OpalMediaFormat::Merge() is performed.

If a format is empty (invalid) it is ignored and does not update the internal variable. In this way only the input or output side can be updated.

The default behaviour updates the inputMediaFormat and outputMediaFormat member variables.

Parameters:

inputMediaFormat	Input media format
outputMediaFormat	Output media format

Reimplemented in OpalPluginFramedAudioTranscoder, OpalPluginStreamedAudioTranscoder, and OpalFramedTranscoder.

virtual PBoolean OpalTranscoder::ExecuteCommand ( const OpalMediaCommand & command ) [virtual]

Execute the command specified to the transcoder. The commands are highly context sensitive, for example VideoFastUpdate would only apply to a video transcoder.

The default behaviour simply returns PFalse.

Parameters:

command

Command to execute.

virtual PINDEX OpalTranscoder::GetOptimalDataFrameSize ( PBoolean input ) const [pure virtual]

Get the optimal size for data frames to be converted. This function returns the size of frames that will be most efficient in conversion. A RTP_DataFrame will attempt to provide or use data in multiples of this size. Note that it may not do so, so the transcoder must be able to handle any sized packets.

Parameters:

input

Flag for input or output data size

Implemented in OpalFramedTranscoder, and OpalStreamedTranscoder.

virtual PBoolean OpalTranscoder::ConvertFrames	(	const RTP_DataFrame &	input,
		RTP_DataFrameList &	output
	)			`[virtual]`

Convert the data from one format to another. This function takes the input data as a RTP_DataFrame and converts it to its output format, placing it (possibly) into multiple RTP_DataFrame objects.

The default behaviour makes sure the output list has only one element in it and calls the Convert() function.

Returns PFalse if the conversion fails.

Parameters:

input	Input data
output	Output data

virtual PBoolean OpalTranscoder::Convert	(	const RTP_DataFrame &	input,
		RTP_DataFrame &	output
	)			`[pure virtual]`

Convert the data from one format to another. This function takes the input data as a RTP_DataFrame and converts it to its output format, placing it into the RTP_DataFrame provided.

Returns PFalse if the conversion fails.

Parameters:

input	Input data
output	Output data

Implemented in OpalFramedTranscoder, and OpalStreamedTranscoder.

static OpalTranscoder* OpalTranscoder::Create	(	const OpalMediaFormat &	srcFormat,
		const OpalMediaFormat &	dstFormat,
		const BYTE *	instance = `NULL`,
		unsigned	instanceLen = `0`
	)			`[static]`

Create an instance of a media conversion function. Returns NULL if there is no registered media transcoder between the two named formats.

Parameters:

srcFormat	Name of source format
dstFormat	Name of destination format
instance	Unique instance identifier for transcoder
instanceLen	Length of instance identifier

static bool OpalTranscoder::SelectFormats	(	const OpalMediaFormatList &	srcFormats,
		const OpalMediaFormatList &	dstFormats,
		const OpalMediaFormatList &	allFormats,
		OpalMediaFormat &	srcFormat,
		OpalMediaFormat &	dstFormat
	)			`[static]`

Find media format(s) for transcoders. This function attempts to find and intermediate media format that will allow two transcoders to be used to get data from the source format to the destination format.

There could be many possible matches between the two lists, so preference is given to the order of the destination formats.

Returns PFalse if there is no registered media transcoder that can be used between the two named formats.

Parameters:

srcFormats	Names of possible source formats
dstFormats	Names of possible destination formats
allFormats	Master list of formats for merging options
srcFormat	Selected source format to be used
dstFormat	Selected destination format to be used

static bool OpalTranscoder::FindIntermediateFormat	(	const OpalMediaFormat &	srcFormat,
		const OpalMediaFormat &	dstFormat,
		OpalMediaFormat &	intermediateFormat
	)			`[static]`

Find media intermediate format for transcoders. This function attempts to find the intermediate media format that will allow two transcoders to be used to get data from the source format to the destination format.

If there is a transcoder that can go directly from the source format to the destination format then the function returns true but the intermediateFormat parmaeter will be an invlid format.

Returns false if there is no registered media transcoder that can be used between the two named formats.

Parameters:

srcFormat	Selected destination format to be used
dstFormat	Selected destination format to be used
intermediateFormat	Intermediate format that can be used

static OpalMediaFormatList OpalTranscoder::GetDestinationFormats ( const OpalMediaFormat & srcFormat ) [static]

Get a list of possible destination media formats for the destination.

Parameters:

srcFormat

Selected source format

static OpalMediaFormatList OpalTranscoder::GetSourceFormats ( const OpalMediaFormat & dstFormat ) [static]

Get a list of possible source media formats for the destination.

Parameters:

dstFormat

Selected destination format

static OpalMediaFormatList OpalTranscoder::GetPossibleFormats ( const OpalMediaFormatList & formats ) [static]

Get a list of possible media formats that can do bi-directional media.

Parameters:

formats

Destination format list

PINDEX OpalTranscoder::GetMaxOutputSize ( ) const [inline]

Get maximum output size.

void OpalTranscoder::SetMaxOutputSize ( PINDEX size ) [inline]

Set the maximum output size.

void OpalTranscoder::SetCommandNotifier ( const PNotifier & notifier ) [inline]

Set a notifier to receive commands generated by the transcoder. The commands are highly context sensitive, for example VideoFastUpdate would only apply to a video transcoder.

Parameters:

notifier

Command to execute.

const PNotifier& OpalTranscoder::GetCommandNotifier ( ) const [inline]

Get the notifier to receive commands generated by the transcoder. The commands are highly context sensitive, for example VideoFastUpdate would only apply to a video transcoder.