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：

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'
}

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" />

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));
}

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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