Vp8FrameSelector.java

/*
 * myLib - https://github.com/taktod/myLib
 * Copyright (c) 2014 ttProject. All rights reserved.
 * 
 * Licensed under The MIT license.
 */
package com.ttProject.frame.vp8;

import org.apache.log4j.Logger;

import com.ttProject.frame.VideoSelector;
import com.ttProject.frame.vp8.type.IntraFrame;
import com.ttProject.frame.vp8.type.KeyFrame;
import com.ttProject.nio.channels.IReadChannel;
import com.ttProject.unit.IUnit;
import com.ttProject.unit.extra.BitLoader;
import com.ttProject.unit.extra.bit.Bit1;
import com.ttProject.unit.extra.bit.Bit19;
import com.ttProject.unit.extra.bit.Bit3;

/**
 * selector for vp8 frame.
 * @author taktod
 */
public class Vp8FrameSelector extends VideoSelector {
	/** logger */
	@SuppressWarnings("unused")
	private Logger logger = Logger.getLogger(Vp8FrameSelector.class);
	/** key frame for ref. */
	private KeyFrame keyFrame = null;
	/**
	 * {@inheritDoc}
	 */
	@Override
	public IUnit select(IReadChannel channel) throws Exception {
		if(channel.position() == channel.size()) {
			return null;
		}
		// get frameType version showframe firstPartsSize from first 3 bytes.
		BitLoader loader = new BitLoader(channel);
		loader.setLittleEndianFlg(true);
		Bit1 frameType = new Bit1();
		Bit3 version = new Bit3();
		Bit1 showFrame = new Bit1();
		Bit19 firstPartSize = new Bit19();
		loader.load(frameType, version, showFrame, firstPartSize);
		Vp8Frame frame = null;
		switch(frameType.get()) {
		case 0: // keyFrame
			frame = new KeyFrame(frameType, version, showFrame, firstPartSize);
			keyFrame = (KeyFrame)frame;
			break;
		case 1: // intraFrame
			if(keyFrame == null) {
				return null;
			}
			frame = new IntraFrame(frameType, version, showFrame, firstPartSize);
			frame.setKeyFrame(keyFrame);
			break;
		default:
			throw new Exception("unexpected frameType:" + frameType.get());
		}
		frame.minimumLoad(channel);
		return frame;
	}

}