掌握安卓APP，轻松修改视频属性细节：从入门到精通

引言

随着移动互联网的快速发展，视频应用在智能手机上的应用越来越广泛。许多用户希望能够在安卓设备上轻松修改视频的属性细节，如调整分辨率、改变播放速度、添加字幕等。本文将为您详细讲解如何通过安卓应用程序实现这些功能，从入门到精通。

一、入门篇

1.1 安装开发环境

在开始之前，您需要安装Android Studio，这是官方推荐的安卓开发工具。安装完成后，您可以通过Android Studio创建一个简单的视频处理应用程序。

// 创建一个简单的视频播放器界面
public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 初始化视频播放器
        VideoView videoView = findViewById(R.id.video_view);
        videoView.setVideoPath("path/to/your/video.mp4");
        videoView.start();
    }
}

1.2 获取视频信息

在修改视频属性之前，我们需要获取视频的基本信息，如分辨率、时长等。可以使用以下代码实现：

import android.media.MediaMetadataRetriever;

public class VideoInfo {
    public static MediaMetadataRetriever getVideoInfo(String videoPath) {
        MediaMetadataRetriever retriever = new MediaMetadataRetriever();
        retriever.setDataSource(videoPath);
        return retriever;
    }
}

1.3 调整视频分辨率

要调整视频分辨率，我们需要修改视频的编码参数。以下代码演示了如何将视频分辨率从720p调整为1080p：

import android.media.MediaCodecInfo;
import android.media.MediaExtractor;
import android.media.MediaFormat;

public class VideoResolutionChanger {
    public static String changeResolution(String videoPath, String targetResolution) {
        MediaExtractor extractor = new MediaExtractor();
        extractor.setDataSource(videoPath);

        int trackIndex = -1;
        for (int i = 0; i < extractor.getTrackCount(); i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("video/")) {
                trackIndex = i;
                break;
            }
        }

        if (trackIndex == -1) {
            return "No video track found";
        }

        extractor.selectTrack(trackIndex);
        MediaCodecInfo codecInfo = MediaCodecInfo.findDecoderForFormat(extractor.getTrackFormat(trackIndex));
        String codecName = codecInfo.getName();

        // Create a new MediaExtractor for the target resolution
        MediaExtractor newExtractor = new MediaExtractor();
        newExtractor.setDataSource(videoPath);
        newExtractor.selectTrack(trackIndex);

        // Create a new MediaCodec for the target resolution
        MediaCodec codec = MediaCodec.createDecoderByType(codecName);
        codec.configure(extractor.getTrackFormat(trackIndex), null, null, 0);

        // Process the video frames and adjust the resolution
        ByteBuffer inputBuffer = codec.getInputBuffer(0);
        ByteBuffer outputBuffer = codec.getOutputBuffer(0);
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

        while (true) {
            int bufferIndex = codec.dequeueInputBuffer(1000);
            if (bufferIndex >= 0) {
                inputBuffer.clear();
                int sampleSize = extractor.readSampleData(inputBuffer, 0);
                if (sampleSize < 0) {
                    codec.queueInputBuffer(bufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    break;
                }
                codec.queueInputBuffer(bufferIndex, 0, sampleSize, extractor.getSampleTime(), 0);
                extractor.advanceSample();
            }

            int outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, 1000);
            if (outputBufferIndex >= 0) {
                // Process the output buffer here
                codec.releaseOutputBuffer(outputBufferIndex, false);
            }

            if (codec.dequeueOutputBuffer(bufferInfo, 0) == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                MediaFormat newFormat = codec.getOutputFormat();
                // Adjust the resolution here
                newFormat.setInteger(MediaFormat.KEY_WIDTH, Integer.parseInt(targetResolution.split("x")[0]));
                newFormat.setInteger(MediaFormat.KEY_HEIGHT, Integer.parseInt(targetResolution.split("x")[1]));
                codec.setOutputFormat(newFormat);
            }
        }

        codec.stop();
        codec.release();

        // Save the processed video
        File outputFile = new File(videoPath.replace(".mp4", "_new.mp4"));
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        ByteBuffer outputData = ByteBuffer.allocate(bufferInfo.size);
        outputData.put(outputBuffer);
        outputData.flip();
        outputStream.write(outputData.array());
        outputStream.close();

        return outputFile.getAbsolutePath();
    }
}

二、进阶篇

2.1 改变视频播放速度

要改变视频播放速度，我们需要修改视频的采样率。以下代码演示了如何将视频播放速度从1倍速调整为1.5倍速：

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

public class VideoSpeedChanger {
    public static String changeSpeed(String videoPath, float targetSpeed) {
        MediaExtractor extractor = new MediaExtractor();
        extractor.setDataSource(videoPath);

        int trackIndex = -1;
        for (int i = 0; i < extractor.getTrackCount(); i++) {
            MediaFormat format = extractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("video/")) {
                trackIndex = i;
                break;
            }
        }

        if (trackIndex == -1) {
            return "No video track found";
        }

        extractor.selectTrack(trackIndex);
        MediaCodecInfo codecInfo = MediaCodecInfo.findDecoderForFormat(extractor.getTrackFormat(trackIndex));
        String codecName = codecInfo.getName();

        // Create a new MediaExtractor for the target speed
        MediaExtractor newExtractor = new MediaExtractor();
        newExtractor.setDataSource(videoPath);
        newExtractor.selectTrack(trackIndex);

        // Create a new MediaCodec for the target speed
        MediaCodec codec = MediaCodec.createDecoderByType(codecName);
        codec.configure(extractor.getTrackFormat(trackIndex), null, null, 0);

        // Process the video frames and adjust the speed
        ByteBuffer inputBuffer = codec.getInputBuffer(0);
        ByteBuffer outputBuffer = codec.getOutputBuffer(0);
        MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

        while (true) {
            int bufferIndex = codec.dequeueInputBuffer(1000);
            if (bufferIndex >= 0) {
                inputBuffer.clear();
                int sampleSize = extractor.readSampleData(inputBuffer, 0);
                if (sampleSize < 0) {
                    codec.queueInputBuffer(bufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    break;
                }
                codec.queueInputBuffer(bufferIndex, 0, sampleSize, extractor.getSampleTime(), 0);
                extractor.advanceSample();
            }

            int outputBufferIndex = codec.dequeueOutputBuffer(bufferInfo, 1000);
            if (outputBufferIndex >= 0) {
                // Process the output buffer here
                codec.releaseOutputBuffer(outputBufferIndex, false);
            }

            if (codec.dequeueOutputBuffer(bufferInfo, 0) == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
                MediaFormat newFormat = codec.getOutputFormat();
                // Adjust the speed here
                newFormat.setFloat(MediaFormat.KEY_SAMPLE_RATE, (float) (newFormat.getInteger(MediaFormat.KEY_SAMPLE_RATE) * targetSpeed));
                codec.setOutputFormat(newFormat);
            }
        }

        codec.stop();
        codec.release();

        // Save the processed video
        File outputFile = new File(videoPath.replace(".mp4", "_new.mp4"));
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        ByteBuffer outputData = ByteBuffer.allocate(bufferInfo.size);
        outputData.put(outputBuffer);
        outputData.flip();
        outputStream.write(outputData.array());
        outputStream.close();

        return outputFile.getAbsolutePath();
    }
}

2.2 添加字幕

要添加字幕，我们需要使用字幕文件和相应的解码器。以下代码演示了如何将SRT字幕文件添加到视频中：

import android.media.MediaCodec;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.text.SpannableStringBuilder;

public class SubtitleAdder {
    public static String addSubtitle(String videoPath, String subtitlePath) {
        MediaExtractor videoExtractor = new MediaExtractor();
        videoExtractor.setDataSource(videoPath);

        MediaExtractor subtitleExtractor = new MediaExtractor();
        subtitleExtractor.setDataSource(subtitlePath);

        int videoTrackIndex = -1;
        for (int i = 0; i < videoExtractor.getTrackCount(); i++) {
            MediaFormat format = videoExtractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("video/")) {
                videoTrackIndex = i;
                break;
            }
        }

        int subtitleTrackIndex = -1;
        for (int i = 0; i < subtitleExtractor.getTrackCount(); i++) {
            MediaFormat format = subtitleExtractor.getTrackFormat(i);
            String mime = format.getString(MediaFormat.KEY_MIME);
            if (mime.startsWith("text/srt")) {
                subtitleTrackIndex = i;
                break;
            }
        }

        if (videoTrackIndex == -1 || subtitleTrackIndex == -1) {
            return "No video or subtitle track found";
        }

        videoExtractor.selectTrack(videoTrackIndex);
        subtitleExtractor.selectTrack(subtitleTrackIndex);

        // Create a new MediaCodec for the video track
        MediaCodec videoCodec = MediaCodec.createDecoderByType(videoExtractor.getTrackFormat(videoTrackIndex).getString(MediaFormat.KEY_MIME));
        videoCodec.configure(videoExtractor.getTrackFormat(videoTrackIndex), null, null, 0);
        videoCodec.start();

        // Create a new MediaCodec for the subtitle track
        MediaCodec subtitleCodec = MediaCodec.createDecoderByType(subtitleExtractor.getTrackFormat(subtitleTrackIndex).getString(MediaFormat.KEY_MIME));
        subtitleCodec.configure(subtitleExtractor.getTrackFormat(subtitleTrackIndex), null, null, 0);
        subtitleCodec.start();

        // Process the video and subtitle streams
        ByteBuffer videoInputBuffer = videoCodec.getInputBuffer(0);
        ByteBuffer subtitleInputBuffer = subtitleCodec.getInputBuffer(0);
        MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo();
        MediaCodec.BufferInfo subtitleBufferInfo = new MediaCodec.BufferInfo();

        while (true) {
            int videoBufferIndex = videoCodec.dequeueInputBuffer(1000);
            if (videoBufferIndex >= 0) {
                videoInputBuffer.clear();
                int sampleSize = videoExtractor.readSampleData(videoInputBuffer, 0);
                if (sampleSize < 0) {
                    videoCodec.queueInputBuffer(videoBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    break;
                }
                videoCodec.queueInputBuffer(videoBufferIndex, 0, sampleSize, videoExtractor.getSampleTime(), 0);
                videoExtractor.advanceSample();
            }

            int subtitleBufferIndex = subtitleCodec.dequeueInputBuffer(1000);
            if (subtitleBufferIndex >= 0) {
                subtitleInputBuffer.clear();
                int sampleSize = subtitleExtractor.readSampleData(subtitleInputBuffer, 0);
                if (sampleSize < 0) {
                    subtitleCodec.queueInputBuffer(subtitleBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    break;
                }
                subtitleCodec.queueInputBuffer(subtitleBufferIndex, 0, sampleSize, subtitleExtractor.getSampleTime(), 0);
                subtitleExtractor.advanceSample();
            }

            int videoOutputBufferIndex = videoCodec.dequeueOutputBuffer(videoBufferInfo, 1000);
            if (videoOutputBufferIndex >= 0) {
                // Process the video output buffer here
                videoCodec.releaseOutputBuffer(videoOutputBufferIndex, false);
            }

            int subtitleOutputBufferIndex = subtitleCodec.dequeueOutputBuffer(subtitleBufferInfo, 1000);
            if (subtitleOutputBufferIndex >= 0) {
                // Process the subtitle output buffer here
                SpannableStringBuilder subtitleText = new SpannableStringBuilder();
                subtitleText.append(subtitleCodec.dequeueOutputBuffer(subtitleBufferInfo, 0));
                subtitleCodec.releaseOutputBuffer(subtitleOutputBufferIndex, false);
            }
        }

        videoCodec.stop();
        videoCodec.release();
        subtitleCodec.stop();
        subtitleCodec.release();

        // Save the processed video with subtitles
        File outputFile = new File(videoPath.replace(".mp4", "_with_subtitle.mp4"));
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        ByteBuffer outputData = ByteBuffer.allocate(videoBufferInfo.size + subtitleBufferInfo.size);
        outputData.put(videoInputBuffer);
        outputData.put(subtitleInputBuffer);
        outputData.flip();
        outputStream.write(outputData.array());
        outputStream.close();

        return outputFile.getAbsolutePath();
    }
}

三、总结

通过以上内容，您已经掌握了如何在安卓应用程序中修改视频属性细节。从入门到进阶，本文为您提供了丰富的示例代码和详细解释。希望这些内容能够帮助您在实际项目中轻松实现视频处理功能。

正文

掌握安卓APP，轻松修改视频属性细节：从入门到精通

引言

一、入门篇

1.1 安装开发环境

1.2 获取视频信息

1.3 调整视频分辨率

二、进阶篇

2.1 改变视频播放速度

2.2 添加字幕

三、总结

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