视频裁剪与矩阵 Android Java

要实现视频裁剪与矩阵操作，可以使用Android的MediaCodec和OpenGL ES。以下是一个示例解决方案：

1. 导入所需的库和类

import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaExtractor;
import android.media.MediaFormat;
import android.opengl.GLES20;
import android.opengl.GLUtils;
import android.opengl.Matrix;

2. 初始化OpenGL ES环境

private int[] textures;
private int program;
private int uMatrixLocation;
private float[] projectionMatrix = new float[16];

private void initOpenGL() {
    // 创建纹理
    textures = new int[1];
    GLES20.glGenTextures(1, textures, 0);
    int texture = textures[0];
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture);
    GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
    GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
    GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
    GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);

    // 创建Shader程序
    program = createProgram(vertexShaderCode, fragmentShaderCode);
    GLES20.glUseProgram(program);
    uMatrixLocation = GLES20.glGetUniformLocation(program, "u_Matrix");

    // 设置投影矩阵
    Matrix.orthoM(projectionMatrix, 0, 0, 1, 0, 1);
    GLES20.glUniformMatrix4fv(uMatrixLocation, 1, false, projectionMatrix, 0);
}

3. 创建视频裁剪方法

private void cropVideo(String inputPath, String outputPath, int startX, int startY, int width, int height) throws Exception {
    // 创建MediaExtractor和MediaCodec
    MediaExtractor extractor = new MediaExtractor();
    extractor.setDataSource(inputPath);
    int trackIndex = selectTrack(extractor);
    extractor.selectTrack(trackIndex);
    MediaFormat format = extractor.getTrackFormat(trackIndex);
    int rotation = format.getInteger(MediaFormat.KEY_ROTATION);
    MediaCodec codec = MediaCodec.createDecoderByType(format.getString(MediaFormat.KEY_MIME));
    codec.configure(format, null, null, 0);
    codec.start();

    // 创建MediaMuxer
    MediaMuxer muxer = new MediaMuxer(outputPath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);

    // 创建ByteBuffer用于存储视频帧数据
    int bufferSize = width * height * 3 / 2;
    ByteBuffer inputBuffer = ByteBuffer.allocate(bufferSize);
    ByteBuffer outputBuffer = ByteBuffer.allocate(bufferSize);
    MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();

    // 循环读取视频帧数据并裁剪
    boolean isInputEnd = false;
    boolean isOutputEnd = false;
    while (!isOutputEnd) {
        if (!isInputEnd) {
            int inputIndex = codec.dequeueInputBuffer(10000);
            if (inputIndex >= 0) {
                inputBuffer.clear();
                int sampleSize = extractor.readSampleData(inputBuffer, 0);
                if (sampleSize < 0) {
                    codec.queueInputBuffer(inputIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
                    isInputEnd = true;
                } else {
                    codec.queueInputBuffer(inputIndex, 0, sampleSize, extractor.getSampleTime(), 0);
                    extractor.advance();
                }
            }
        }

        if (!isOutputEnd) {
            int outputIndex = codec.dequeueOutputBuffer(bufferInfo, 10000);
            if (outputIndex >= 0) {
                if (bufferInfo.size > 0) {
                    outputBuffer.clear();
                    outputBuffer.put(inputBuffer);
                    outputBuffer.position(bufferInfo.offset);
                    outputBuffer.limit(bufferInfo.offset + bufferInfo.size);

                    // 裁剪视频帧
                    cropFrame(outputBuffer, startX, startY, width, height, rotation);

                    muxer.writeSampleData(0, outputBuffer, bufferInfo);
                }

                codec.releaseOutputBuffer(outputIndex, false);

                if ((bufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                    isOutputEnd = true;
                }
            }
        }
    }

    // 释放资源
    muxer.stop();
    muxer.release