概述

最近在做的一个需求就是视频检测，通过使用百度的MCA媒体内容分析这一个视频检测产品来做的。

我们的产品暂时有一个限制就是：用户上传的视频长度不能超过10分钟。而视频是前端上传到阿里云OSS的，然后拿着这个阿里云OSS视频URL扔给百度，提交给百度去做视频分析。

需求细化：给定一个在线URL视频，获取其视频帧长度。一般情况下，给定本地的视频文件，获取其视频长度，没啥难度。

调研下来，使用大名鼎鼎的FFmpeg框架，一个基于C语言的，提供多媒体转码、音视频流化传输等功能的开源框架可满足需求。

实战

获取在线URL视频时长

通过Java执行cmd命令：ffmpeg.exe -i '视频url地址'

private static String COLON = ":";
private static String REGEX_DURATION = ":";

public static Integer getUrlVideoLength(String url) {
    // ffmpeg命令位置
    String ffmpeg = "/usr/bin/ffmpeg";
    String os = System.getProperty("os.name");
    if (StrUtil.containsIgnoreCase(os, ArmConstant.WINDOWS)) {
        ffmpeg = "D:\\soft\\ffmpeg-4.4-essentials_build\\bin\\ffmpeg.exe";
    }
    // 拼接系统命令
    List<String> commands = new ArrayList<>();
    commands.add(ffmpeg);
    commands.add("-i");
    commands.add(url);

    ProcessBuilder builder = new ProcessBuilder();
    builder.command(commands);
    try {
        final Process p = builder.start();
        // 从输出流中读取视频信息
        BufferedReader br = new BufferedReader(new InputStreamReader(p.getErrorStream()));
        StringBuilder sb = new StringBuilder();
        String line;
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }
        br.close();
        Pattern pattern = Pattern.compile(REGEX_DURATION);
        Matcher m = pattern.matcher(sb.toString());
        if (m.find()) {
            return getSecond(m.group(1));
        }
    } catch (Exception e) {
        log.error("getUrlVideoLength failed: " + e.getMessage());
    }
    return 0;
}

/**
 * 获取秒,加括号调整运算符优先级
 *
 * @param time format as 00:04:01.13
 */
private static Integer getSecond(String time) {
    boolean check = StrUtil.isEmpty(time) || time.length() != 11;
    if (check) {
        return 0;
    }
    String secondPart = time.split(COLON)[2];
    return 3600 * Integer.parseInt(time.split(COLON)[0]) +
            60 * Integer.parseInt(time.split(COLON)[1]) +
            Integer.parseInt(secondPart.substring(0, secondPart.indexOf("."))) +
            (Integer.parseInt(secondPart.substring(secondPart.indexOf(".") + 1)) > 0 ? 1 : 0);
}

上面的sb，即为ffmpeg.exe -i '视频url地址'命令的输出为：

ffmpeg version 4.4-essentials_build-www.gyan.dev Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10.2.0 (Rev6, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\迅雷下载\1c883613c8d74e4cbe3b40e6bdaae8.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.58.101
  Duration: 00:00:20.69, start: 0.000000, bitrate: 482 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 368x640, 442 kb/s, 24 fps, 24 tbr, 12288 tbn, 96 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 43 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
At least one output file must be specified

可知时长为：Duration: 00:04:01.13