javax.media
接口 Codec

所有超级接口：

Controls, PlugIn

所有已知子接口：

Effect

所有已知实现类：

BasicCodec

public interface Codec
extends PlugIn

A Codec is a media processing unit that accepts a Buffer object as its input, performs some processing on the input data, and then puts the result in an output Buffer object. It has one input and one output. Typical examples of codecs include audio decoders, video encoders, and effects.

A codec usually works in one of the following modes:

• Frame based mode. In this mode, the codec accepts one frame of data from its input and converts it to one frame of output data. The codec must consume its input Buffer and generate an output Buffer.

  This mode is useful when the codec can handle any size of input. A simple gain codec fits this model: it multiplies each sample with the gain factor and puts the product in an output Buffer. Another scenario where this mode is useful is when the codec can only process data that's in a fixed, pre-determined frame size and the input Buffer is already packetized accordingly. One example of such a codec is a GSM audio decoder, which accepts a compressed GSM audio packet from an RTP depacketizer, decodes the packet, and then puts the result in an output Buffer.
  

• Stream based mode. In this mode, the codec accepts chunks of data from its input and might generate an output Buffer. The codec might consume only part of the input Buffer each time its process method is called and might not generate an output Buffer during each round of processing. This mode is useful in stream packetizers, which accept a stream of bytes and divide the stream into packets (frames) that are used in the next processing phase. Another scenario where this mode is useful is when two audio processing units that have incompatible frame sizes need to be chained.

Some restrictions apply to the processing a Codec can perform on its input and output Buffer objects:

• The Codec might receive an output Buffer that is not big enough to hold its output data. In this case, the Codec should allocate a new Buffer for its output data.
  
• The Codec cannot cache references to Buffer object fields. It must read all of the parameters from the input and output Buffer objects each time its process method is called.
  
• If the Codec needs to keep references to a Buffer object's data (for performance reasons), the Codec must assign other data to the input Buffer object by calling setData before returning from the process method. The data assigned can be null, but it is better to assign some unneeded data to the Buffer, such as input data received earlier. Such manipulations can be used for in-place processing (where the output of the processing is put in the same location as input data in order to enhance memory utilization) or for codecs that need access to more than one frame of data without copying the data (for example, temporal video effects).

从以下版本开始：

JMF 2.0

字段摘要

从接口 javax.media.PlugIn 继承的字段

BUFFER_PROCESSED_FAILED, BUFFER_PROCESSED_OK, INPUT_BUFFER_NOT_CONSUMED, OUTPUT_BUFFER_NOT_FILLED, PLUGIN_TERMINATED

方法摘要

Format[]	getSupportedInputFormats() Lists all of the input formats that this codec accepts.
Format[]	getSupportedOutputFormats(Format input) Lists the output formats that this codec can generate.
int	process(Buffer input, Buffer output) Performs the media processing defined by this codec.
Format	setInputFormat(Format format) Sets the format of the data to be input to this codec.
Format	setOutputFormat(Format format) Sets the format for the data this codec outputs.

从接口 javax.media.PlugIn 继承的方法

close, getName, open, reset

从接口 javax.media.Controls 继承的方法

getControl, getControls

方法详细信息

getSupportedInputFormats

Format[] getSupportedInputFormats()

Lists all of the input formats that this codec accepts.

返回：

An array that contains the supported input Formats.

getSupportedOutputFormats

Format[] getSupportedOutputFormats(Format input)

Lists the output formats that this codec can generate. If input is non-null, this method lists the possible output formats that can be generated from input data of the specified Format. If input is null, this method lists all of the output formats supported by this plug-in.

参数：

input - The Format of the data to be used as input to the plug-in.

返回：

An array that contains the supported output Formats.

setInputFormat

Format setInputFormat(Format format)

Sets the format of the data to be input to this codec.

参数：

format - The Format to be set.

返回：

The Format that was set, which might be the supported Format that most closely matches the one specified. Returns null if the specified Format is not supported and no reasonable match could be found.

setOutputFormat

Format setOutputFormat(Format format)

Sets the format for the data this codec outputs.

参数：

format - The Format to be set.

返回：

The Format that was set, which might be the Format that most closely matched the one specified. Returns null if the specified Format is not supported and no reasonable match could be found.

process

int process(Buffer input,
            Buffer output)

Performs the media processing defined by this codec.

参数：

input - The Buffer that contains the media data to be processed.

output - The Buffer in which to store the processed media data.

返回：

BUFFER_PROCESSED_OK if the processing is successful. Other possible return codes are defined in PlugIn.

另请参见：

PlugIn