How to pull RTSP streams using FFmpeg

Using FFmpeg in Java to pull an RTSP stream and push it to another target address is a relatively complex task because Java itself does not have the ability to directly handle video streams. However, we can use the FFmpeg command line tool to implement this function. FFmpeg is a very powerful multimedia processing tool that can handle audio, video, and other multimedia files and streams.

To call FFmpeg in Java, we usually useProcessBuilderor().exec()to execute the FFmpeg command. In this example, we will show how to useProcessBuilderTo pull the RTSP stream and push it to another RTSP server.

Prerequisites

• Install FFmpeg: Make sure that FFmpeg is installed on your system and that it can be accessed from the command line.
• RTSP source and target: Make sure you have a valid RTSP source URL and a target RTSP server URL.

Code Example 1

Here is a complete Java sample code showing how to use itProcessBuilderTo call the FFmpeg command, pull the video stream from the RTSP source and push it to another RTSP server.

import ;
import ;
import ;
 
public class FFmpegRTSPStreamer {
 
    public static void main(String[] args) {
        // RTSP source and destination URLs
        String rtspSourceUrl = "rtsp://your_source_ip:port/stream";
        String rtspDestinationUrl = "rtsp://your_destination_ip:port/stream";
 
        // FFmpeg command to pull RTSP stream and push to another RTSP server
        String ffmpegCommand = (
                "ffmpeg -i %s -c copy -f rtsp %s",
                rtspSourceUrl, rtspDestinationUrl
        );
 
        // Create a ProcessBuilder to execute the FFmpeg command
        ProcessBuilder processBuilder = new ProcessBuilder(
                "bash", "-c", ffmpegCommand
        );
 
        // Redirect FFmpeg's stderr to the Java process's standard output
        (true);
 
        try {
            // Start the FFmpeg process
            Process process = ();
 
            // Create BufferedReader to read the output from FFmpeg process
            BufferedReader reader = new BufferedReader(new InputStreamReader(()));
            String line;
            while ((line = ()) != null) {
                (line);
            }
 
            // Wait for the process to complete
            int exitCode = ();
            ("\nFFmpeg process exited with code: " + exitCode);
 
        } catch (IOException | InterruptedException e) {
            ();
        }
    }
}

Code example one description and precautions

(I) Explanation

RTSP URLs：

• rtspSourceUrl: Your RTSP source address.
• rtspDestinationUrl: Your target RTSP server address.

FFmpeg command:

• ffmpeg -i <source> -c copy -f rtsp <destination>: This is the basic command format for FFmpeg, which is used to pull streams from source and copy to destination.-c copyIt means that the stream is not recoded and the stream is copied directly.

ProcessBuilder：

• We useProcessBuilderTo build and execute FFmpeg commands. Since FFmpeg is a command line tool, weProcessBuilderSpecified inbash -cto execute the FFmpeg command.
• redirectErrorStream(true)Redirect FFmpeg's stderr to stdout so that we can see the output of FFmpeg in our Java program.

BufferedReader：

We useBufferedReaderTo read the output of the FFmpeg process and print it to the console of the Java program.

Wait for the process to complete:

use()Wait for the FFmpeg process to complete and get its exit code.

(II) Things to note

• Path issues: Make sure the FFmpeg command is found in your system path. If FFmpeg is not in the system path, you need to provide the full path to FFmpeg.
• Error handling: Error handling in the sample code is relatively simple, you can add more detailed error handling logic as needed.
• performance: Calling the FFmpeg command directly in Java may be limited by the communication efficiency between the Java process and the FFmpeg process. For high performance requirements, you may want to consider using JNI or other underlying integration methods.

Code Example 2

Here is a more detailed Java code example that includes more error handling, logging, and asynchronous monitoring of the FFmpeg process.

(I) Code Example

First, we need to introduce some classes in the Java standard library, such asProcess, BufferedReader, InputStreamReader, OutputStream, Threadwait. In addition, to simplify logging, we can use JavaBag.

import .*;
import .*;
import .*;
 
public class FFmpegRTSPStreamer {
 
    private static final Logger logger = (());
 
    public static void main(String[] args) {
        // RTSP source and destination URLs
        String rtspSourceUrl = "rtsp://your_source_ip:port/path";
        String rtspDestinationUrl = "rtsp://your_destination_ip:port/path";
 
        // FFmpeg command to pull RTSP stream and push to another RTSP server
        // Note: Make sure ffmpeg is in your system's PATH or provide the full path to ffmpeg
        String ffmpegCommand = (
                "ffmpeg -re -i %s -c copy -f rtsp %s",
                rtspSourceUrl, rtspDestinationUrl
        );
 
        // Use a thread pool to manage the FFmpeg process
        ExecutorService executorService = ();
        Future<?> future = (() -> {
            try {
                ProcessBuilder processBuilder = new ProcessBuilder("bash", "-c", ffmpegCommand);
                (true);
 
                Process process = ();
 
                // Read FFmpeg's output asynchronously
                BufferedReader reader = new BufferedReader(new InputStreamReader(()));
                String line;
                while ((line = ()) != null) {
                    (line);
                }
 
                // Wait for the process to complete
                int exitCode = ();
                ("FFmpeg process exited with code: " + exitCode);
 
            } catch (IOException | InterruptedException e) {
                (, "Error running FFmpeg process", e);
            }
        });
 
        // Optionally, add a timeout to the FFmpeg process
        // This will allow the program to terminate the FFmpeg process if it runs for too long
        ScheduledExecutorService scheduler = (1);
        (() -> {
            if (!()) {
                ("FFmpeg process timed out and will be terminated");
                (true); // This will interrupt the thread running FFmpeg
                // Note: This won't actually kill the FFmpeg process, just the Java thread monitoring it.
                // To kill the FFmpeg process, you would need to find its PID and use `()` or an OS-specific command.
            }
        }, 60, ); // Set the timeout duration as needed
 
        // Note: The above timeout mechanism is not perfect because `(true)` only interrupts the Java thread.
        // To properly handle timeouts and killing the FFmpeg process, you would need to use a different approach,
        // such as running FFmpeg in a separate process group and sending a signal to that group.
 
        // In a real application, you would want to handle the shutdown of these ExecutorServices gracefully,
        // for example, by adding shutdown hooks or providing a way to stop the streaming via user input.
 
        // For simplicity, this example does not include such handling.
    }
}

(II) Things to note

• Logging:I usedTo record the log. This allows you to better monitor the output of the FFmpeg process and any potential errors.
• Thread pool: I used a single threadedExecutorServiceTo run the FFmpeg process. This allows you to manage the lifecycle of a process more easily and can cancel it if needed (although the cancellation mechanism above is not perfect as it just interrupts the Java thread that monitors FFmpeg).
• Asynchronous output read: The output of FFmpeg is read asynchronously, which means that the Java program will not block and wait for FFmpeg to complete, but will continue to execute and process the output of FFmpeg in the background.
• Timeout processing: I added an optional timeout mechanism, but please note that this mechanism is not perfect. It will only interrupt the Java thread that monitors FFmpeg, and will not actually kill the FFmpeg process. To correctly implement the timeout and kill the FFmpeg process, you need to use operating system-specific commands or signals.
• Clean up: In the example above, I did not includeExecutorServiceandScheduledExecutorServiceCleanup code. In actual applications, you should make sure that these services are closed correctly when they are no longer needed.
• Path issues: Make sure the FFmpeg command can be found in your system path, or provide the full path to FFmpeg.
• Error handling: The error handling in the example is relatively simple. In actual applications, you may need to add more detailed error handling logic, such as retry mechanisms, more detailed logging, etc.
• performance: Calling the FFmpeg command directly in Java may be limited by the communication efficiency between the Java process and the FFmpeg process. For high performance requirements, you may want to consider using JNI or other underlying integration methods. However, for most use cases, the above approach should be efficient enough.

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