视频流添加文本合成字幕

　　通过Java CV框架的FFmpegFrameGrabber读取本地一个视频流的帧，接着Java2DFrameConverter先把帧转换为图片，由Graphics2D进行文本刷到图片上后，Java2DFrameConverter再把合成的图片转回帧，最后由FFmpegFrameRecorder把帧写入输出视频流。

　　直接上代码：

package com.lxy.service;

import org.bytedeco.ffmpeg.global.avcodec;
import org.bytedeco.javacv.*;
import org.bytedeco.javacv.Frame;
import org.bytedeco.opencv.opencv_core.*;
import sun.font.FontDesignMetrics;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class LiveMixService {

    public static void main(String[] args) throws FrameGrabber.Exception, FrameRecorder.Exception {
        // 构造测试字幕
        String[] test = {
                "世上无难事",
                "只怕有心人",
                "只要思想不滑坡",
                "办法总比困难多",
                "长江后浪推前浪",
                "前浪死在沙滩上"
        };

        // 为连续的50帧设置同一个测试字幕
        List<String> testStr = new ArrayList<>();
        for (int i = 0; i < 300; i++) {
            testStr.add(test[i / 50]);
        }

        // 设置源视频、加字幕后的视频
        FFmpegFrameGrabber grabber = FFmpegFrameGrabber.createDefault("E:\\BaiduNetdiskDownload\\testout.mkv");
        FFmpegFrameRecorder recorder = FFmpegFrameRecorder.createDefault("E:\\BaiduNetdiskDownload\\outtest.mp4",
                1280, 720);
        System.out.println("准备开始推流...");
        grabber.start();
        recorder.start();
        Java2DFrameConverter converter = new Java2DFrameConverter();
        Frame frame = null;
        int i = 0;
        while ((frame = grabber.grabImage()) != null) {
            // 从视频帧中获取图片
            BufferedImage bufferedImage = converter.getBufferedImage(frame);
            bufferedImage = addSubtitle(bufferedImage, testStr.get(i++ % 300));
            frame.image = converter.getFrame(bufferedImage).image;
            recorder.record(frame);
        }
        grabber.stop();
        recorder.stop();
    }

    /**
     * 图片添加文本
     * @param bufImg
     * @param subTitleContent
     * @return
     */
    private static BufferedImage addSubtitle(BufferedImage bufImg, String subTitleContent) {

        // 添加字幕时的时间
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        Font font = new Font("微软雅黑", Font.BOLD, 32);
        String timeContent = sdf.format(new Date());
        FontDesignMetrics metrics = FontDesignMetrics.getMetrics(font);
        Graphics2D graphics = bufImg.createGraphics();
        graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));

        //设置图片背景
        graphics.drawImage(bufImg, 0, 0, bufImg.getWidth(), bufImg.getHeight(), null);

        //设置左上方时间显示
        graphics.setColor(Color.orange);
        graphics.setFont(font);
        graphics.drawString(timeContent, 0, metrics.getAscent());

        // 计算文字长度，计算居中的x点坐标
        int textWidth = metrics.stringWidth(subTitleContent);
        int widthX = (bufImg.getWidth() - textWidth) / 2;
        graphics.setColor(Color.red);
        graphics.setFont(font);
        graphics.drawString(subTitleContent, widthX, bufImg.getHeight() - 50);
        graphics.dispose();
        return bufImg;
    }
}

　　看下效果：