Android MedieCodec硬解碼mp3,wma

1MedieCodec支持4.1以上系統使用,是谷歌SDK的一個類。

2能夠對mp3,wma格式音頻文件解碼

3解碼前，需要MediaExactor提取文件信息，包括文件類型，采樣率，

package com.dawin.mediacodec;

import java.io.IOException;
import java.nio.ByteBuffer;

import android.media.MediaCodec;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.media.MediaCodec.BufferInfo;

public class MediaCodecTest
{
	byte[] decodeData = new byte[1024 * 1024 * 20];// 20m
	MediaCodec mMediaCodec;
	MediaExtractor mediaExtractor;
	MediaFormat mMediaFormat;
	final int TIMEOUT_US = 1000;
	BufferInfo info;
	boolean sawOutputEOS = false;
	boolean sawInputEOS = false;
	ByteBuffer[] codecInputBuffers;
	ByteBuffer[] codecOutputBuffers;

	/**
	 * 解碼音頻文件，返回最後解碼的數據
	 * 
	 * @param url
	 * @return
	 */
	public byte[] decode(String url)
	{
		url = "";
		try
		{
			mediaExtractor.setDataSource(url);
		} catch (IOException e)
		{
		}
		mMediaFormat = mediaExtractor.getTrackFormat(0);
		String mime = mMediaFormat.getString(MediaFormat.KEY_MIME);
		try
		{
			mMediaCodec = MediaCodec.createDecoderByType(mime);
		} catch (IOException e)
		{
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		mMediaCodec.configure(mMediaFormat, null, null, 0);
		mMediaCodec.start();

		codecInputBuffers = mMediaCodec.getInputBuffers();
		codecOutputBuffers = mMediaCodec.getOutputBuffers();

		info = new BufferInfo();
		mediaExtractor.selectTrack(0);
		input();
		output();
		return decodeData;
	}

	private void output()
	{
		final int res = mMediaCodec.dequeueOutputBuffer(info, TIMEOUT_US);
		if (res >= 0)
		{
			int outputBufIndex = res;
			ByteBuffer buf = codecOutputBuffers[outputBufIndex];

			final byte[] chunk = new byte[info.size];
			buf.get(chunk); // Read the buffer all at once
			buf.clear(); // ** MUST DO!!! OTHERWISE THE NEXT TIME YOU GET THIS
							// SAME BUFFER BAD THINGS WILL HAPPEN

			if (chunk.length > 0)
			{
				System.arraycopy(chunk, 0, decodeData, 0, chunk.length);
				// mAudioTrack.write(chunk, 0, chunk.length);
			}
			mMediaCodec.releaseOutputBuffer(outputBufIndex, false /* render */);

			if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0)
			{
				sawOutputEOS = true;
			}
		} else if (res == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED)
		{
			codecOutputBuffers = mMediaCodec.getOutputBuffers();
		} else if (res == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED)
		{
			final MediaFormat oformat = mMediaCodec.getOutputFormat();
			// Log.d(LOG_TAG, "Output format has changed to " + oformat);
			// mAudioTrack.setPlaybackRate(oformat.getInteger(MediaFormat.KEY_SAMPLE_RATE));
		}

	}

	private void input()
	{

		int inputBufIndex = mMediaCodec.dequeueInputBuffer(TIMEOUT_US);

		if (inputBufIndex >= 0)
		{
			ByteBuffer dstBuf = codecInputBuffers[inputBufIndex];

			int sampleSize = mediaExtractor.readSampleData(dstBuf, 0);
			// Log.i(LOG_TAG, "sampleSize : "+sampleSize);
			long presentationTimeUs = 0;
			if (sampleSize < 0)
			{
				// .Log.i(LOG_TAG, "Saw input end of stream!");
				sawInputEOS = true;
				sampleSize = 0;
			} else
			{
				presentationTimeUs = mediaExtractor.getSampleTime();
				// Log.i(LOG_TAG, "presentationTimeUs "+presentationTimeUs);
			}

			mMediaCodec.queueInputBuffer(inputBufIndex,
					0, // offset
					sampleSize, presentationTimeUs,
					sawInputEOS ? MediaCodec.BUFFER_FLAG_END_OF_STREAM : 0);
			if (!sawInputEOS)
			{
				// Log.i(LOG_TAG, "extractor.advance()");
				mediaExtractor.advance();

			}
		}

	}
}