用 Java + FFmpeg 实现 MP4 转 m3u8：初学者友好指南 🎓

ffmpeg -i input.mp4 \
  -codec: copy \
  -hls_time 10 \
  -hls_list_size 0 \
  -start_number 0 \
  -f hls output.m3u8

String cmd = String.join(" ", Arrays.asList(
  "ffmpeg -i", inputMp4,
  "-codec: copy",
  "-hls_time 10",
  "-hls_list_size 0",
  "-start_number 0",
  "-f hls", outputM3u8
));
ProcessBuilder pb = new ProcessBuilder(cmd.split(" "));
pb.redirectErrorStream(true);
Process process = pb.start();
// 读取 process.getInputStream()，并等待结束

ffmpeg -i input.mp4 \
  -force_key_frames "expr:gte(t,n_forced*4)" \
  -hls_time 4 \
  ...

public boolean convertMp4ToM3u8(String mp4, String outDir) throws IOException, InterruptedException {
    Files.createDirectories(Paths.get(outDir));
    String m3u8Path = outDir + "/video.m3u8";
    List<String> cmd = Arrays.asList(
      "ffmpeg", "-i", mp4,
      "-codec: copy",
      "-force_key_frames", "expr:gte(t,n_forced*6)",
      "-hls_time", "6",
      "-hls_list_size", "0",
      "-start_number", "0",
      "-f", "hls", m3u8Path
    );
    ProcessBuilder pb = new ProcessBuilder(cmd);
    Process process = pb.inheritIO().start();
    int code = process.waitFor();
    return code == 0;
}