Android Multimedia框架总结（二十三）MediaCodec补充及MediaMuxer引入（附案例）

Posted 2020-08-24 码农突围

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.videoclip
D/VideoClip: >>　url : /storage/emulated/0/节目.mp4
12-18 19:04:49.364 22409-22409/com.hejunlin.videoclip
D/VideoClip: width and height is 480 272;maxInputSize is 25326;duration is 125266666
12-18 19:04:49.365 22409-22409/com.hejunlin.videoclip
D/VideoClip: file mime is video/avc
12-18 19:04:49.366 22409-22409/com.hejunlin.videoclip
D/VideoClip: sampleRate is 24000;channelCount is 2;audioMaxInputSize is 348;audioDuration is 125440000
12-18 19:04:49.366 22409-22409/com.hejunlin.videoclip
D/VideoClip: file mime is audio/mp4a-latm
12-18 19:04:49.370 22409-22409/com.hejunlin.videoclip
D/VideoClip: videoSampleTime is 66667
12-18 19:04:49.372 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 0;sampleFlag is 1;sampleSize is 19099
12-18 19:04:49.373 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 66666;sampleFlag is 0;sampleSize is 451
12-18 19:04:49.374 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 133333;sampleFlag is 0;sampleSize is 521
12-18 19:04:49.374 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 200000;sampleFlag is 0;sampleSize is 738
12-18 19:04:49.375 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 266666;sampleFlag is 0;sampleSize is 628
12-18 19:04:49.376 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 333333;sampleFlag is 0;sampleSize is 267
12-18 19:04:49.376 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 400000;sampleFlag is 0;sampleSize is 4003
12-18 19:04:49.377 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 466666;sampleFlag is 0;sampleSize is 2575
12-18 19:04:49.377 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 533333;sampleFlag is 0;sampleSize is 1364
12-18 19:04:49.378 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 600000;sampleFlag is 0;sampleSize is 3019
12-18 19:04:49.379 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 666666;sampleFlag is 0;sampleSize is 4595
12-18 19:04:49.379 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 0;presentationTimeUs is 733333;sampleFlag is 0;sampleSize is 3689
... 省略log
12-18 19:04:49.467 22409-22409/com.hejunlin.videoclip
D/VideoClip: AudioSampleTime is 42667
12-18 19:04:49.468 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 1;presentationTimeUs is 2005333
12-18 19:04:49.469 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 1;presentationTimeUs is 2048000
12-18 19:04:49.469 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 1;presentationTimeUs is 2090666
12-18 19:04:49.470 22409-22409/com.hejunlin.videoclip
D/VideoClip: trackIndex is 1;presentationTimeUs is 2133333
12-18 19:04:49.470 22409-22409/com.hejunlin.videoclip
... 省略log
D/VideoClip: trackIndex is 1;presentationTimeUs is 12032000

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