在Java中使用ffmpeg作为进程录制直播流

Question

我不知道如何在Java中启动一个进程来使用ffmpeg录制实况流。

我已经尝试了几种解决方案，但我当前的代码看起来像这样(简化)：

public void startDownload() {
    String[] processArgs = new String[] {
            "ffmpeg", 
            "-i", 
            "https://bitdash-a.akamaihd.net/content/sintel/hls/playlist.m3u8", 
            "-c", 
            "copy", 
            "-bsf:a", 
            "aac_adtstoasc", 
            "C:\\temp\\test.mp4"
    };
    ProcessBuilder processBuilder = new ProcessBuilder(processArgs);
    try {
        process = processBuilder.start();
        process.wairFor(); // Do I need this? Actually the stream is running forever until I stop it manually.
        BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String line = null;
        while ((line = br.readLine()) != null) { // this blocks forever
            System.out.println(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

问题是，有些东西阻止了这个过程的启动。在本例中，br.readLine()将永远阻塞它，并且我无法从该进程中获得任何输出。

但在Intellij中终止jar /停止启动配置后，进程开始工作，我必须通过任务管理器终止它。

顺便说一句，运行一个不记录实况流的进程，就像执行ffmpeg一样。

我用的是Windows，jdk14，IntelliJ。

Answer 1

我自己就能弄明白。您必须将输入流和输出流都通过管道传输到BufferedReader，并且需要读取它的所有行。

我的代码目前看起来像这样：

public void startDownload() {
    String[] processArgs = new String[] {
            "ffmpeg", 
            "-i", 
            "https://bitdash-a.akamaihd.net/content/sintel/hls/playlist.m3u8", 
            "-c", 
            "copy", 
            "-bsf:a", 
            "aac_adtstoasc", 
            "C:\\temp\\test.mp4"
    };
    ProcessBuilder processBuilder = new ProcessBuilder(processArgs);
    process = processBuilder.start();

    BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
    BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
    String line = "";
    String newLineCharacter = System.getProperty("line.separator");

    boolean isOutReady = false;
    boolean isErrorReady = false;

    boolean isErrorOut = true;
    boolean isErrorError = true;

    boolean isPrintToConsole = false;

    while (process.isAlive()) {
        do {
            isOutReady = stdInput.ready();
            isErrorOut = true;
            isErrorError = true;

            if (isOutReady) {
                line = stdInput.readLine();
                isErrorOut = false;
                if (isPrintToConsole) {
                    System.out.println(line + newLineCharacter);
                }
            }
            isErrorReady = stdError.ready();
            if (isErrorReady) {
                line = stdError.readLine();
                isErrorError = false;
                if (isPrintToConsole) {
                    System.out.println("ERROR: " + line + newLineCharacter);
                }

            }
            if (!process.isAlive()) {
                if (isPrintToConsole) {
                    System.out.println("Process DIE: " + line + newLineCharacter);
                }
                line = null;
                isErrorError = false;
                process.waitFor();
            }
        } while (line != null);

        process.waitFor(100, TimeUnit.MILLISECONDS);
    }
}