请尊重分享成果，转载请注明出处,本文来自逆流的鱼yuiop,原文链接：http://blog.csdn.net/hejjunlin/article/details/53729575
前言：前面几章都是分析MediaCodec相关源码，有收到提问，说MediaCodec到底是硬解码还是软解码？看下今天的Agenda:
MediaCodec到底是硬解码还是软解码MediaMuxer初识MediaMuxer与MediaExtractor进行剪辑视频效果图布局实现逻辑实现log输出过程MediaCodec到底是硬解码还是软解码？
MediaCodec 调用的是在系统中register的解码器，硬件厂商会把自己的硬解码器register进来，就是硬解，如果他register一个软解码器，则是软解。
MediaCodec并不是真正的codec，真正codec是在openMax，要保证是硬解，在MediaCodec里有接口可以枚举所有解码器，每种编码可能都有多个解码器，区分哪个是软解哪个是硬解就行。
MediaCodec mediaCodec = MediaCodec.createDecoderByType("video/avc");我的应用里面接收的是H264编码数据，所以我选取的是video/avc，我们可以看一下MediaCodec.createDecoderByType（）枚举了哪些解编码器：
> /**> * Instantiate a decoder supporting input data of the given mime type.> *> * The following is a partial list of defined mime types and their semantics:> * <ul>> * <li>"video/x-vnd.on2.vp8" - VP8 video (i.e. video in .webm)> * <li>"video/x-vnd.on2.vp9" - VP9 video (i.e. video in .webm)> * <li>"video/avc" - H.264/AVC video> * <li>"video/mp4v-es" - MPEG4 video> * <li>"video/3gpp" - H.263 video> * <li>"audio/3gpp" - AMR narrowband audio> * <li>"audio/amr-wb" - AMR wideband audio> * <li>"audio/mpeg" - MPEG1/2 audio layer III> * <li>"audio/mp4a-latm" - AAC audio (note, this is raw AAC packets, not packaged in LATM!)> * <li>"audio/vorbis" - vorbis audio> * <li>"audio/g711-alaw" - G.711 alaw audio> * <li>"audio/g711-mlaw" - G.711 ulaw audio> * </ul>> *> * @param type The mime type of the input data.> */> public static MediaCodec createDecoderByType(String type) {> return new MediaCodec(type, true /* nameIsType */, false /* encoder */);> }可以看到我选的”video/avc” – H.264/AVC video是一种H264的解码方式，但并不能证明我使用的就一定是硬解码
我们先来看一下Android系统中解码器的命名，软解码器通常是以OMX.google开头的。硬解码器通常是以OMX.[hardware_vendor]开头的，比如TI的解码器是以OMX.TI开头的。当然还有一些不遵守这个命名规范的，不以OMX.开头的，那也会被认为是软解码器。
判断规则见frameworks/av/media/libstagefright/OMXCodec.cpp：
static bool IsSoftwareCodec(const char *componentName) { if (!strncmp("OMX.google.", componentName, 11)) { return true; } if (!strncmp("OMX.", componentName, 4)) { return false; } return true;}其实MediaCodec调用的是在系统中注册的解码器，系统中存在的解码器可以很多，但能够被应用使用的解码器是根据配置来的，即/system/etc/media_codecc.xml。这个文件一般由硬件或者系统的生产厂家在build整个系统的时候提供，一般是保存在代码的device/[company]/[codename]目录下的，例如device/samsung/tuna/media_codecs.xml。这个文件配置了系统中有哪些可用的codec以及，这些codec对应的媒体文件类型。在这个文件里面，系统里面提供的软硬codec都需要被列出来。
也就是说，如果系统里面实际上包含了某个codec，但是并没有被配置在这个文件里，那么应用程序也无法使用到。
在这个配置文件里面，如果出现多个codec对应同样类型的媒体格式的时候，这些codec都会被保留起来。当系统使用的时候，将会选择第一个匹配的codec。除非是指明了要软解码还是硬解码，但是Android的framework层为上层提供服务的AwesomePlayer中在处理音频和视频的时候，对到底是选择软解还是硬解的参数没有设置。所以虽然底层是支持选择的，但是对于上层使用MediaPlayer的Java程序来说，还是只能接受默认的codec选取规则。
但是Android提供的命令行程序/system/bin/stagefright在播放音频文件的时候，倒是可以根据参数来选择到底使用软解码还是硬解码，但是该工具只支持播放音频，不支持播放视频。
一般来说，如果系统里面有对应的媒体硬件解码器的话，系统开发人员应该是会配置在media_codecs.xml中，所以大多数情况下，如果有硬件解码器，那么我们总是会使用到硬件解码器。极少数情况下，硬件解码器存在，但不配置，我猜只可能是这个硬解码器还有bug，暂时还不适合发布，所以不用使用。
MediaMuxer初识
今天主要介绍MediaMuxer，在Android的多媒体类中，MediaMuxer用于将音频和视频进行混合生成多媒体文件。缺点是目前只能支持一个audio track和一个video track，而且仅支持mp4输出。 通过一个案列来了解MediaMuxer，以便后续过程分析，这个案例是进行一个音视频剪辑。就是一段正常的音视频文件，剪辑其中一个片段。在我的手机上有一段叫《节目.mp4》音视频文件。想剪辑其中精华部分，从2秒到12秒的视频。如下为效果图
效果图：
输入剪辑时间点，可以动态设置，并不是写死，剪辑时长，也是可以动态设置。
节目_output.mp4就是剪辑后的音视频文件。
布局实现：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="10dp" android:orientation="horizontal"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="18sp" android:text="开始剪辑点(从第几秒开始):"/> <EditText android:id="@+id/et_cutpoint" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@null" android:textSize="18sp" android:layout_marginLeft="5dp" android:hint="2"/> </LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="10dp" android:orientation="horizontal"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="18sp" android:text="剪辑时长(剪辑多少秒):"/> <EditText android:id="@+id/et_cutduration" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@null" android:textSize="18sp" android:layout_marginLeft="5dp" android:hint="10"/> </LinearLayout> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/button" android:padding="10dp" android:background="@drawable/selector_green_bg" android:layout_gravity="center" android:textColor="@color/white" android:text="剪切视频" /></LinearLayout>本文来自逆流的鱼yuiop,原文链接：http://blog.csdn.net/hejjunlin/article/details/53729575
逻辑实现：
package com.hejunlin.videoclip;import android.media.MediaCodec;import android.media.MediaExtractor;import android.media.MediaFormat;import android.media.MediaMuxer;import android.util.Log;import java.nio.ByteBuffer;/** * Created by 逆流的鱼yuiop on 16/12/18. * blog : http://blog.csdn.net/hejjunlin */public class VideoClip { private final static String TAG = "VideoClip"; private MediaExtractor mMediaExtractor; private MediaFormat mMediaFormat; private MediaMuxer mMediaMuxer; private String mime = null; public boolean clipVideo(String url, long clipPoint, long clipDuration) { int videoTrackIndex = -1; int audioTrackIndex = -1; int videoMaxInputSize = 0; int audioMaxInputSize = 0; int sourceVTrack = 0; int sourceATrack = 0; long videoDuration, audioDuration; Log.d(TAG, ">> url : " + url); //创建分离器 mMediaExtractor = new MediaExtractor(); try { //设置文件路径 mMediaExtractor.setDataSource(url); //创建合成器 mMediaMuxer = new MediaMuxer(url.substring(0, url.lastIndexOf(".")) + "_output.mp4", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4); } catch (Exception e) { Log.e(TAG, "error path" + e.getMessage()); } //获取每个轨道的信息 for (int i = 0; i < mMediaExtractor.getTrackCount(); i++) { try { mMediaFormat = mMediaExtractor.getTrackFormat(i); mime = mMediaFormat.getString(MediaFormat.KEY_MIME); if (mime.startsWith("video/")) { sourceVTrack = i; int width = mMediaFormat.getInteger(MediaFormat.KEY_WIDTH); int height = mMediaFormat.getInteger(MediaFormat.KEY_HEIGHT); videoMaxInputSize = mMediaFormat.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE); videoDuration = mMediaFormat.getLong(MediaFormat.KEY_DURATION); //检测剪辑点和剪辑时长是否正确 if (clipPoint >= videoDuration) { Log.e(TAG, "clip point is error!"); return false; } if ((clipDuration != 0) && ((clipDuration + clipPoint) >= videoDuration)) { Log.e(TAG, "clip duration is error!"); return false; } Log.d(TAG, "width and height is " + width + " " + height + ";maxInputSize is " + videoMaxInputSize + ";duration is " + videoDuration ); //向合成器添加视频轨 videoTrackIndex = mMediaMuxer.addTrack(mMediaFormat); } else if (mime.startsWith("audio/")) { sourceATrack = i; int sampleRate = mMediaFormat.getInteger(MediaFormat.KEY_SAMPLE_RATE); int channelCount = mMediaFormat.getInteger(MediaFormat.KEY_CHANNEL_COUNT); audioMaxInputSize = mMediaFormat.getInteger(MediaFormat.KEY_MAX_INPUT_SIZE); audioDuration = mMediaFormat.getLong(MediaFormat.KEY_DURATION); Log.d(TAG, "sampleRate is " + sampleRate + ";channelCount is " + channelCount + ";audioMaxInputSize is " + audioMaxInputSize + ";audioDuration is " + audioDuration ); //添加音轨 audioTrackIndex = mMediaMuxer.addTrack(mMediaFormat); } Log.d(TAG, "file mime is " + mime); } catch (Exception e) { Log.e(TAG, " read error " + e.getMessage()); } } //分配缓冲 ByteBuffer inputBuffer = ByteBuffer.allocate(videoMaxInputSize); //根据官方文档的解释MediaMuxer的start一定要在addTrack之后 mMediaMuxer.start(); //视频处理部分 mMediaExtractor.selectTrack(sourceVTrack); MediaCodec.BufferInfo videoInfo = new MediaCodec.BufferInfo(); videoInfo.presentationTimeUs = 0; long videoSampleTime; //获取源视频相邻帧之间的时间间隔。(1) { mMediaExtractor.readSampleData(inputBuffer, 0); //skip first I frame if (mMediaExtractor.getSampleFlags() == MediaExtractor.SAMPLE_FLAG_SYNC) mMediaExtractor.advance(); mMediaExtractor.readSampleData(inputBuffer, 0); long firstVideoPTS = mMediaExtractor.getSampleTime(); mMediaExtractor.advance(); mMediaExtractor.readSampleData(inputBuffer, 0); long SecondVideoPTS = mMediaExtractor.getSampleTime(); videoSampleTime = Math.abs(SecondVideoPTS - firstVideoPTS); Log.d(TAG, "videoSampleTime is " + videoSampleTime); } //选择起点 mMediaExtractor.seekTo(clipPoint, MediaExtractor.SEEK_TO_PREVIOUS_SYNC); while (true) { int sampleSize = mMediaExtractor.readSampleData(inputBuffer, 0); if (sampleSize < 0) { //这里一定要释放选择的轨道，不然另一个轨道就无法选中了 mMediaExtractor.unselectTrack(sourceVTrack); break; } int trackIndex = mMediaExtractor.getSampleTrackIndex(); //获取时间戳 long presentationTimeUs = mMediaExtractor.getSampleTime(); //获取帧类型，只能识别是否为I帧 int sampleFlag = mMediaExtractor.getSampleFlags(); Log.d(TAG, "trackIndex is " + trackIndex + ";presentationTimeUs is " + presentationTimeUs + ";sampleFlag is " + sampleFlag + ";sampleSize is " + sampleSize); //剪辑时间到了就跳出 if ((clipDuration != 0) && (presentationTimeUs > (clipPoint + clipDuration))) { mMediaExtractor.unselectTrack(sourceVTrack); break; } mMediaExtractor.advance(); videoInfo.offset = 0; videoInfo.size = sampleSize; videoInfo.flags = sampleFlag; mMediaMuxer.writeSampleData(videoTrackIndex, inputBuffer, videoInfo); videoInfo.presentationTimeUs += videoSampleTime;//presentationTimeUs; } //音频部分 mMediaExtractor.selectTrack(sourceATrack); MediaCodec.BufferInfo audioInfo = new MediaCodec.BufferInfo(); audioInfo.presentationTimeUs = 0; long audioSampleTime; //获取音频帧时长 { mMediaExtractor.readSampleData(inputBuffer, 0); //skip first sample if (mMediaExtractor.getSampleTime() == 0) mMediaExtractor.advance(); mMediaExtractor.readSampleData(inputBuffer, 0); long firstAudioPTS = mMediaExtractor.getSampleTime(); mMediaExtractor.advance(); mMediaExtractor.readSampleData(inputBuffer, 0); long SecondAudioPTS = mMediaExtractor.getSampleTime(); audioSampleTime = Math.abs(SecondAudioPTS - firstAudioPTS); Log.d(TAG, "AudioSampleTime is " + audioSampleTime); } mMediaExtractor.seekTo(clipPoint, MediaExtractor.SEEK_TO_CLOSEST_SYNC); while (true) { int sampleSize = mMediaExtractor.readSampleData(inputBuffer, 0); if (sampleSize < 0) { mMediaExtractor.unselectTrack(sourceATrack); break; } int trackIndex = mMediaExtractor.getSampleTrackIndex(); long presentationTimeUs = mMediaExtractor.getSampleTime(); Log.d(TAG, "trackIndex is " + trackIndex + ";presentationTimeUs is " + presentationTimeUs); if ((clipDuration != 0) && (presentationTimeUs > (clipPoint + clipDuration))) { mMediaExtractor.unselectTrack(sourceATrack); break; } mMediaExtractor.advance(); audioInfo.offset = 0; audioInfo.size = sampleSize; mMediaMuxer.writeSampleData(audioTrackIndex, inputBuffer, audioInfo); audioInfo.presentationTimeUs += audioSampleTime;//presentationTimeUs; } //全部写完后释放MediaMuxer和MediaExtractor mMediaMuxer.stop(); mMediaMuxer.release(); mMediaExtractor.release(); mMediaExtractor = null; return true; }}ClipActivity
package com.hejunlin.videoclip;import android.annotation.TargetApi;import android.os.Build;import android.os.Bundle;import android.os.Environment;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Button;import android.widget.EditText;/** * Created by 逆流的鱼yuiop on 16/12/18. * blog : http://blog.csdn.net/hejjunlin */public class ClipActivity extends AppCompatActivity implements View.OnClickListener { private Button mButton; private EditText mCutDuration; private EditText mCutPoint; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main1); mButton = (Button) findViewById(R.id.button); mCutDuration = (EditText) findViewById(R.id.et_cutduration); mCutPoint = (EditText)findViewById(R.id.et_cutpoint); mButton.setOnClickListener(this); } @TargetApi(Build.VERSION_CODES.LOLLIPOP) @Override public void onClick(View v) { new VideoClip().clipVideo( Environment.getExternalStorageDirectory() + "/" + "节目.mp4", Integer.parseInt(mCutPoint.getText().toString())*1000*1000, Integer.parseInt(mCutDuration.getText().toString())*1000*1000); }}log输出过程
12-18 19:04:49.212 22409-22409/com.hejunlin.videoclipD/VideoClip: >> url : /storage/emulated/0/节目.mp412-18 19:04:49.364 22409-22409/com.hejunlin.videoclipD/VideoClip: width and height is 480 272;maxInputSize is 25326;duration is 12526666612-18 19:04:49.365 22409-22409/com.hejunlin.videoclipD/VideoClip: file mime is video/avc12-18 19:04:49.366 22409-22409/com.hejunlin.videoclipD/VideoClip: sampleRate is 24000;channelCount is 2;audioMaxInputSize is 348;audioDuration is 12544000012-18 19:04:49.366 22409-22409/com.hejunlin.videoclipD/VideoClip: file mime is audio/mp4a-latm12-18 19:04:49.370 22409-22409/com.hejunlin.videoclipD/VideoClip: videoSampleTime is 6666712-18 19:04:49.372 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 0;sampleFlag is 1;sampleSize is 1909912-18 19:04:49.373 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 66666;sampleFlag is 0;sampleSize is 45112-18 19:04:49.374 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 133333;sampleFlag is 0;sampleSize is 52112-18 19:04:49.374 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 200000;sampleFlag is 0;sampleSize is 73812-18 19:04:49.375 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 266666;sampleFlag is 0;sampleSize is 62812-18 19:04:49.376 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 333333;sampleFlag is 0;sampleSize is 26712-18 19:04:49.376 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 400000;sampleFlag is 0;sampleSize is 400312-18 19:04:49.377 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 466666;sampleFlag is 0;sampleSize is 257512-18 19:04:49.377 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 533333;sampleFlag is 0;sampleSize is 136412-18 19:04:49.378 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 600000;sampleFlag is 0;sampleSize is 301912-18 19:04:49.379 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 666666;sampleFlag is 0;sampleSize is 459512-18 19:04:49.379 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 0;presentationTimeUs is 733333;sampleFlag is 0;sampleSize is 3689... 省略log12-18 19:04:49.467 22409-22409/com.hejunlin.videoclipD/VideoClip: AudioSampleTime is 4266712-18 19:04:49.468 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 1;presentationTimeUs is 200533312-18 19:04:49.469 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 1;presentationTimeUs is 204800012-18 19:04:49.469 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 1;presentationTimeUs is 209066612-18 19:04:49.470 22409-22409/com.hejunlin.videoclipD/VideoClip: trackIndex is 1;presentationTimeUs is 213333312-18 19:04:49.470 22409-22409/com.hejunlin.videoclip... 省略logD/VideoClip: trackIndex is 1;presentationTimeUs is 12032000第一时间获得博客更新提醒，以及更多android干货，源码分析，欢迎关注我的微信公众号，扫一扫下方二维码或者长按识别二维码，即可关注。
如果你觉得好，随手点赞，也是对笔者的肯定，也可以分享此公众号给你更多的人，原创不易
活在当下，别在怀念过去或者憧憬未来中浪费掉你现在的生活。
![[置顶] Android Multimedia框架总结（二十三）MediaCodec](https://www.note234.com/wp-content/themes/generatepress/images/92.jpg)