使用ffmpeg生成视频后返回路径至index.js时显示undefined

我尝试用FFmpeg生成视频，将生成后的视频路径返回给index.js，但控制台打印的路径始终是undefined。

index.js 代码 #

app.get('/content/:myfact', async (req, res) => {
  let myfactdata = req.params.myfact;
  let myfact = myfactdata.replace("_", " ");
  const video = await generateVideo(myfact);
  console.log(video)
});

contentVideo.js 代码 #

const generateImage = require('./contentimage.js');
const { spawn } = require('child_process');

const generateVideo = async (myfact) => {
  await generateImage(myfact);
  const child = spawn('ffmpeg', [
    '-i', 'pictures/download/image.png', 'pictures/download/video.mp4'
  ]);
  child.on('close', function (code, signal) {
    const video = 'pictures/download/video.mp4'
    return video
  });
}

module.exports = generateVideo

问题核心是generateVideo的异步逻辑处理错误：

• spawn是异步执行的，你在child.on('close')回调里的return，不会成为generateVideo函数的返回值
• 原函数没有返回任何Promise，导致index.js里的await无法获取异步操作的结果，最终得到undefined

修改contentVideo.js，将spawn的异步逻辑包装为Promise，让函数返回这个Promise：

const generateImage = require('./contentimage.js');
const { spawn } = require('child_process');

const generateVideo = async (myfact) => {
  await generateImage(myfact);
  
  return new Promise((resolve, reject) => {
    const child = spawn('ffmpeg', [
      '-i', 'pictures/download/image.png', 'pictures/download/video.mp4'
    ]);
    
    child.on('close', (code, signal) => {
      if (code === 0) {
        resolve('pictures/download/video.mp4');
      } else {
        reject(new Error(`FFmpeg执行失败，退出码：${code}，信号：${signal}`));
      }
    });
    
    child.on('error', (err) => {
      reject(new Error(`启动FFmpeg失败：${err.message}`));
    });
  });
}

module.exports = generateVideo

修改说明 #

1. 将FFmpeg调用逻辑包裹在Promise中，用resolve返回成功后的视频路径，reject抛出执行错误
2. 增加错误处理：通过退出码判断FFmpeg是否执行成功，同时监听启动失败的error事件
3. 函数直接返回Promise，确保index.js里的await能正确获取到视频路径

内容的提问来源于stack exchange，提问作者Satyam Kumar