FFMPEG 如何复制音频文件或裁剪到特定长度

问题描述

我想要将一个有音频的视频文件和一个音频文件合并，得到一个输出文件。

最重要的是，我需要做到以下几点：

如果视频文件的长度更长，则需要增加音频文件的长度至相同。

如果音频文件长度比视频文件长，则需要将音频文件裁剪至与视频长度相同。

示例：

视频长度为2分5秒

音频长度为1分钟 – > 复制为2分5秒

若:

视频长度为1分钟

音频长度为2分5秒 – > 裁剪为1分钟

但是，我甚至无法增加音频文件的长度。

export async function overlayAudio(id: number, music: Music) {
  console.log('start')
  const videoPath = path.join(__dirname, `../../../uploads/movie/{id}/result/movie/predfinal.mp4`);

  if (music === null) {
    return videoPath.match(/\\uploads(.*)/)[0];
  } else {
    const audioPath = path.join(__dirname, `../../../{music.audio}`);
    const outputVideoPath = path.join(__dirname, `../../../uploads/movie/{id}/result/movie/output.mp4`);
    const matchPath = outputVideoPath.match(/\\uploads(.*)/);
    const cmd = `ffmpeg -i{videoPath} -i {audioPath} -filter_complex "[0:a]volume=1[a];[1:a]volume=0.2[b];[b]apad[looped_audio];[a][looped_audio]amix=inputs=2:duration=longest" -c:v copy -c:a aac -strict experimental -shortest{outputVideoPath}`;

    try {
      await execPromise(cmd);
      console.log('end!')
      return matchPath[0];
    } catch (error) {
      console.error('Error:', error);
      throw error;
    }
  }
}

解决方案

export async function overlayAudio(id: number, music: Music) {
  console.log("start");

  const videoPath = path.join(
    __dirname,
    `../../../uploads/movie/{id}/result/movie/predfinal.mp4`
  );

  if (music === null) {
    return videoPath.match(/\\uploads(.*)/)[0];
  } else {
    const audioPath = path.join(__dirname, `../../../{music.audio}`);

    const outputVideoPath = path.join(
      __dirname,
      `../../../uploads/movie/{id}/result/movie/output.mp4`
    );

    const matchPath = outputVideoPath.match(/\\uploads(.*)/);
    const videoDurationCmd = `ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1{videoPath}`;
    const audioDurationCmd = `ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 {audioPath}`;

    const [videoDuration, audioDuration] = await Promise.all([
      execPromise(videoDurationCmd),
      execPromise(audioDurationCmd),
    ]);

    // Calculate the time difference
    const videoDurationValue = parseFloat(videoDuration);
    const audioDurationValue = parseFloat(audioDuration);
    const durationDifference = videoDurationValue - audioDurationValue;

    let cmd;
    if (durationDifference>0) { // If ideo is longer than audio
      cmd = `ffmpeg -i{videoPath} -i {audioPath} -filter_complex "[0:a]volume=1[a];[1:a]volume=0.2[b];[b]apad[looped_audio];[a][looped_audio]amix=inputs=2:duration=first:dropout_transition=2" -c:v copy -c:a aac -strict experimental{outputVideoPath}`;
    } else if (durationDifference < 0) { // If audio is longer than video
      cmd = `ffmpeg -i {videoPath} -i{audioPath} -filter_complex "[0:a]volume=1[a];[1:a]volume=0.2[b];[b]apad[looped_audio];[a][looped_audio]amix=inputs=2:duration=first:dropout_transition=2" -c:v copy -c:a aac -strict experimental -t {videoDurationValue}{outputVideoPath}`;
    } else { // If no need to adjust
      cmd = `ffmpeg -i {videoPath} -i{audioPath} -filter_complex "[0:a]volume=1[a];[1:a]volume=0.2[b];[b]apad[looped_audio];[a][looped_audio]amix=inputs=2:duration=first:dropout_transition=2" -c:v copy -c:a aac -strict experimental ${outputVideoPath}`;
    }

    try {
      await execPromise(cmd);
      console.log("end!");
      return matchPath[0];
    } catch (error) {
      console.error("Error:", error);
      throw error;
    }
  }
}