android mp4parser怎样进行视频分辨率调整

要使用Android的MP4Parser库调整视频分辨率，请按照以下步骤操作：

1. 首先，确保已将MP4Parser库添加到项目的依赖项中。在app的build.gradle文件中添加以下依赖项：

dependencies {

    implementation 'com.googlecode.mp4parser:mp4parser:1.5.0'
}
    

1. 在AndroidManifest.xml文件中添加写入外部存储的权限：

<
    uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    

1. 在需要调整分辨率的Activity中，编写一个方法来调整视频分辨率：

import android.media.MediaMetadata;
    
import android.media.MediaCodec;
    
import android.media.MediaFormat;
    
import com.googlecode.mp4parser.AbstractContainer;
    
import com.googlecode.mp4parser.Container;
    
import com.googlecode.mp4parser.FileChannelWrapper;
    
import com.googlecode.mp4parser.Movie;
    
import com.googlecode.mp4parser.MutableInteger;
    
import com.googlecode.mp4parser.Track;
    
import com.googlecode.mp4parser.VideoCodecCore;
    
import java.io.File;
    
import java.io.FileOutputStream;
    
import java.io.IOException;
    
import java.nio.ByteBuffer;


public void resizeVideo(String inputPath, String outputPath, int newWidth, int newHeight) throws IOException {
    
    File inputFile = new File(inputPath);
    
    Container container = new Container(new FileChannelWrapper(new FileInputStream(inputFile)));
    
    Movie movie = new Movie();


    for (Track track : container.getTracks()) {

        if (track.getHandler().toString().contains("Video")) {
    
            MediaFormat format = MediaFormat.createVideoFormat(MediaFormat.MIMETYPE_VIDEO_AVC, newWidth, newHeight);
    
            VideoCodecCore codec = new VideoCodecCore();
    
            MediaCodec mediaCodec = MediaCodec.createByCodecName("avc1");
    
            mediaCodec.configure(format, null, null, 0);
    
            mediaCodec.start();
    
            MutableInteger bufferSize = new MutableInteger(0);
    
            ByteBuffer[] inputBuffers = mediaCodec.getInputBuffers();
    
            int trackIndex = container.getTracks().indexOf(track);
    
            long startTime = 0;
    
            long endTime = 0;
    
            for (int i = 0;
     i <
     movie.getTracks().size();
 i++) {

                if (movie.getTracks().get(i).equals(track)) {
    
                    startTime = movie.getTracks().get(i).getSampleDescriptionBox().getSampleEntryTime();
    
                    endTime = movie.getTracks().get(i).getLastSampleEntryTime();
    
                    break;

                }

            }
    
            long sampleTime = startTime;
    
            while (sampleTime <
 endTime) {
    
                int inputBufferIndex = mediaCodec.dequeueInputBuffer(-1);
    
                if (inputBufferIndex >
= 0) {
    
                    ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
    
                    int sampleSize = container.readSampleData(inputBuffer, 0);
    
                    if (sampleSize <
 0) {
    
                        break;

                    }
    
                    inputBuffer.limit(sampleSize);
    
                    mediaCodec.queueInputBuffer(inputBufferIndex, 0, sampleSize, sampleTime, 0);
    
                    sampleTime += sampleSize;

                }

            }
    
            MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

            while (mediaCodec.dequeueOutputBuffer(bufferInfo, 0) == MediaCodec.BUFFER_FLAG_END_OF_STREAM) {
    
                ByteBuffer outputBuffer = mediaCodec.getOutputBuffer(bufferInfo.outputBufferIndex);
    
                outputBuffer.position(bufferInfo.offset);
    
                outputBuffer.limit(bufferInfo.offset + bufferInfo.size);
    
                FileOutputStream fos = new FileOutputStream(outputPath);
    
                FileChannelWrapper outputChannel = new FileChannelWrapper(fos);
    
                outputChannel.write(outputBuffer);
    
                outputChannel.close();
    
                mediaCodec.releaseOutputBuffer(bufferInfo.outputBufferIndex, false);

            }
    
            mediaCodec.stop();
    
            mediaCodec.release();

        }
    
        movie.addTrack(track);

    }
    
    movie.writeContainer(new FileOutputStream(outputPath));

}
    

1. 调用resizeVideo方法，传入输入视频路径、输出视频路径以及新的宽度和高度：

String inputPath = "path/to/input/video.mp4";
    
String outputPath = "path/to/output/video.mp4";
    
int newWidth = 1280;
    
int newHeight = 720;


try {
    
    resizeVideo(inputPath, outputPath, newWidth, newHeight);

}
 catch (IOException e) {
    
    e.printStackTrace();

}
    

这将使用MP4Parser库将输入视频调整为指定的新分辨率，并将调整后的视频保存到输出路径。

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