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ost::AudioCodec

NAME

ost::AudioCodec − The codec class is a virtual used for transcoding audio samples between linear frames (or other known format) and an encoded ’sample’ buffer.

SYNOPSIS

#include <audio2.h>

Inherits ost::Audio.

Public Member Functions

AudioCodec (const char *name, Encoding encoding)
Base for codecs, create a named coded of a specific encoding.

virtual ~AudioCodec ()
virtual Level getImpulse (void *buffer, unsigned number=0)
Get the impulse energy level of a frame of X samples in the specified codec format.

virtual Level getPeak (void *buffer, unsigned number=0)
Get the peak energy level within the frame of X samples.

virtual bool isSilent (Level threashold, void *buffer, unsigned number=0)
Signal if the current audio frame is silent.

virtual unsigned encode (Linear buffer, void *dest, unsigned number=0)=0
Encode a linear sample frame into the codec sample buffer.

virtual unsigned encodeBuffered (Linear Buffer, Encoded dest, unsigned number)
Encode linear samples buffered into the coded.

virtual unsigned decode (Linear buffer, void *source, unsigned number=0)=0
Decode the sample frame into linear samples.

virtual unsigned decodeBuffered (Linear buffer, Encoded source, unsigned len)
Buffer and decode data into linear samples.

virtual unsigned getEstimated (void)
Get estimated data required for buffered operations.

virtual unsigned getRequired (void)
get required samples for encoding.

virtual unsigned getPacket (Encoded destination, Encoded data, unsigned size)
Get a packet of data rather than decode.

Info getInfo
(void)
Get an info description for this codec.

Static Public Member Functions

static void endCodec (AudioCodec *codec)
End use of a requested codec.

static AudioCodec * getCodec (Encoding encoding, const char *format=NULL, bool loaded=false)
Get the codec base class for accessing a specific derived codec identified by encoding type and optional spd info.

static AudioCodec * getCodec (Info &info, bool loaded=false)
Get the codec base class for accessing a specific derived codec identified by audio source descriptor.

static bool load (const char *name)
Load a named codec set into process memory.

static bool load (Encoding encoding)
Find and load a codec file by it’s encoding type.

Protected Member Functions

AudioCodec ()
virtual AudioCodec * getByFormat (const char *format)
often used to create a ’new’ codec of a subtype based on encoding format, default returns the current codec entity.

virtual AudioCodec * getByInfo (Info &info)
get a codec by audio source info descriptor.

Protected Attributes

AudioCodec * next
Encoding encoding

const char * name
Info info

Static Protected Attributes

static AudioCodec * first

Detailed Description

The codec class is a virtual used for transcoding audio samples between linear frames (or other known format) and an encoded ’sample’ buffer.

This class is only abstract and describes the core interface for loadable codec modules. This class is normally merged with AudioSample. A derived AudioCodecXXX will typically include a AudioRegisterXXX static class to automatically initialize and register the codec with the codec registry.

Author:

David Sugar <dyfet AT ostel DOT com> process codec interface.

Constructor & Destructor Documentation

ost::AudioCodec::AudioCodec () [protected]
ost::AudioCodec::AudioCodec (const char * name, Encoding encoding)

Base for codecs, create a named coded of a specific encoding.

Parameters:

name of codec.
encoding
type of codec.

virtual ost::AudioCodec::~AudioCodec () [inline, virtual]

Member Function Documentation

virtual AudioCodec* ost::AudioCodec::getByFormat (const char * format) [inline, protected, virtual]
often used to create a ’new’ codec of a subtype based on encoding format, default returns the current codec entity.

Returns:

pointer to an active codec or NULL if not found.

Parameters:

format name from spd.

virtual AudioCodec* ost::AudioCodec::getByInfo (Info & info) [inline, protected, virtual]
get a codec by audio source info descriptor.

Returns:

pointer to an active codec or NULL if not found.

Parameters:

info audio source descriptor.

static void ost::AudioCodec::endCodec (AudioCodec * codec) [static]
End use of a requested codec.

If constructed then will be deleted.

Parameters:

codec pointer to getCodec returned coded pointer.

static AudioCodec* ost::AudioCodec::getCodec (Encoding encoding, const char * format = NULL, bool loaded = false) [static]
Get the codec base class for accessing a specific derived codec identified by encoding type and optional spd info.

Returns:

pointer to codec for processing.

Parameters:

encoding format requested.
format
spd options to pass to codec being created.
loaded
true to load if not already in memory.

static AudioCodec* ost::AudioCodec::getCodec (Info & info, bool loaded = false) [static]
Get the codec base class for accessing a specific derived codec identified by audio source descriptor.

Returns:

pointer to codec for processing.

Parameters:

info source descriptor for codec being requested.
loaded
true to load codec if not already in memory.

static bool ost::AudioCodec::load (const char * name) [static]
Load a named codec set into process memory.

Returns:

true if successful.

Parameters:

name of codec set to load.

static bool ost::AudioCodec::load (Encoding encoding) [static]
Find and load a codec file by it’s encoding type.

Converts the type into a codec name and invokes the other loader...

Returns:

true if successful.

Parameters:

encoding type for file.

virtual Level ost::AudioCodec::getImpulse (void * buffer, unsigned number = 0) [virtual]
Get the impulse energy level of a frame of X samples in the specified codec format.

Returns:

average impulse energy of frame (sumnation).

Parameters:

buffer of encoded samples.
number
of encoded samples.

virtual Level ost::AudioCodec::getPeak (void * buffer, unsigned number = 0) [virtual]
Get the peak energy level within the frame of X samples.

Returns:

peak energy impulse in frame (largest).

Parameters:

buffer of encoded samples.
number
of encoded samples.

virtual bool ost::AudioCodec::isSilent (Level threashold, void * buffer, unsigned number = 0) [virtual]
Signal if the current audio frame is silent.

This can be deterimed either by an impulse computation, or, in some cases, some codecs may signal and flag silent packets.

Returns:

true if silent

Parameters:

threashold to use if not signaled.
buffer
of encoded samples.
number
of encoded samples.

virtual unsigned ost::AudioCodec::encode (Linear buffer, void * dest, unsigned number = 0) [pure virtual]
Encode a linear sample frame into the codec sample buffer.

Returns:

number of bytes written.

Parameters:

buffer linear sample buffer to use.
dest
buffer to store encoded results.
number
of samples.

virtual unsigned ost::AudioCodec::encodeBuffered (Linear Buffer, Encoded dest, unsigned number) [virtual]
Encode linear samples buffered into the coded.

Returns:

number of bytes written or 0 if incomplete.

Parameters:

buffer linear samples to post.
destination
of encoded audio.
number
of samples being buffered.

virtual unsigned ost::AudioCodec::decode (Linear buffer, void * source, unsigned number = 0) [pure virtual]
Decode the sample frame into linear samples.

Returns:

number of bytes scanned or returned

Parameters:

buffer sample buffer to save linear samples into.
source
for encoded data.
number
of samples to extract.

virtual unsigned ost::AudioCodec::decodeBuffered (Linear buffer, Encoded source, unsigned len) [virtual]
Buffer and decode data into linear samples.

This is needed for audio formats that have irregular packet sizes.

Returns:

number of samples actually decoded.

Parameters:

destination for decoded data.
source
for encoded data.
number
of bytes being sent.

virtual unsigned ost::AudioCodec::getEstimated (void) [virtual]
Get estimated data required for buffered operations.

Returns:

estimated number of bytes required for decode.

virtual unsigned ost::AudioCodec::getRequired (void) [virtual]
get required samples for encoding.

Returns:

required number of samples for encoder buffer.

virtual unsigned ost::AudioCodec::getPacket (Encoded destination, Encoded data, unsigned size) [virtual]
Get a packet of data rather than decode.

This is tied with getEstimated.

Returns:

size of data packet or 0 if not complete.

Parameters:

destination to save.
data
to push into buffer.
number
of bytes to push.

Info ost::AudioCodec::getInfo (void) [inline]
Get an info description for this codec.

Returns:

info.

Member Data Documentation

AudioCodec* ost::AudioCodec::first [static, protected]
AudioCodec* ost::AudioCodec::next
[protected]
Encoding ost::AudioCodec::encoding
[protected]
const char* ost::AudioCodec::name
[protected]
Info ost::AudioCodec::info
[protected]

Author

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