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/*
* Copyright (C) 2010 Preston Lacey http://javaflacencoder.sourceforge.net/
* All Rights Reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
package javaFlacEncoder;
/**
* Description: This abstract class declares the methods needed to retrieve
* encoded data in a standard format(across the different implemented Subframe
* types), as well as the generic methods needed to write the subframe header.
* It is assumed that objects of this type will be reused in future frames,
* rather than being destroyed and made anew. This is to avoid the overhead
* associated with creating and destroying objects in Java.
* @author Preston Lacey
*/
public abstract class Subframe {
/** StreamConfiguration used for encoding. The same StreamConfiguration
* MUST be used throughout an entire FLAC stream */
protected StreamConfiguration sc;
/** EncodingConfiguration used for encoding. This may be altered between
* frames, but must be the same for each subframe within that frame */
protected EncodingConfiguration ec;
/** Store for size of last subframe encoded(in bits). */
protected int lastEncodedSize;
/**
* Constructor is private to prevenet it's use, as a subframe is not usable
* without first setting a StreamConfiguration(therefore, use other
* constructor.
*/
private Subframe() {
}
/**
* Constructor. Sets StreamConfiguration to use. If the StreamConfiguration
* must later be changed, a new Subframe object must be created as well. A
* default EncodingConfiguration is created using EncodingConfiguration's
* default Constructor. This configuration should create a decent encode,
* but may be altered if desired.
*
* @param sc StreamConfiguration to use for encoding.
*/
public Subframe(StreamConfiguration sc) {
this.sc = sc;
ec = new EncodingConfiguration();
}
/**
* This method is used to set the encoding configuration.
* @param ec encoding configuration to use.
* @return true if configuration was changed, false otherwise
*/
public boolean registerConfiguration(EncodingConfiguration ec) {
this.ec = ec;
return true;
}
/**
* Encodes samples into the appropriate compressed format, saving the result
* in the given “data” EncodedElement list. Encodes 'count' samples, from
* index 'start', to index 'start' times 'skip', where “skip” is the format
* that samples may be packed in an array. For example, 'samples' may
* include both left and right samples of a stereo stream, while this
* SubFrame is only encoding the 'right' channel(channel 2). Therefore,
* “skip” would equal 2, resulting in the valid indices being only those
* where “index mod 2 equals 1”.
* @param samples the audio samples to encode. This array may contain
* samples for multiple channels, interleaved; only one of these channels is
* encoded by a subframe.
* @param count the number of samples to encode.
* @param start the index to start at in the array.
* @param skip the number of indices to skip between successive samples
* (for use when channels are interleaved in the given
* array).
* @param data the EncodedElement to attach encoded data to. Data in
* EncodedElement given is not altered. New data is
* attached starting with “data.getNext()”. If “data”
* already has a “next” set, it will be lost!
* @param offset
* @param bitsPerSample Number of bits per single-channel sample. This may
* differ from the StreamConfiguration's sample size, depending on the
* subframe used(i.e, the "side-channel" of a FLAC stream uses one extra bit
* compared to the input channels).
*
* @return number of encoded samples, or negative value indicating
* an error has occurred.
*
*/
public abstract int encodeSamples(int[] samples, int count, int start, int skip,
EncodedElement data, int offset, int bitsPerSample);
/**
* Returns the total number of valid bits used in the last encoding(i.e, the
* number of compressed bits used). This is here for convenience, as the
* calling object may also loop through the resulting EncodingElement from
* the encoding process and sum the valid bits.
*
* @return an integer with value of the number of bits used in last
* encoding.
*/
public int getEncodedSize() {
return lastEncodedSize;
}
}
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