Stream image from Android with FFMPEG

Here is a JAVA implementation that resembles the Python code:

The example writes raw video frames (byte arrays) to stdin pipe of FFmpeg sub-process:

 _____________             ___________                  ________ 
| JAVA byte   |           |           |                |        |
| Array       |   stdin   | FFmpeg    |                | Output |
| BGR (format)| --------> | process   | -------------> | stream |
|_____________| raw frame |___________| encoded video  |________|

Main stages:

• Initialize FFmpeg command arguments:

   final String command[] = {"ffmpeg", "-f", "rawvideo", ...}
  

• Create ProcessBuilder that executes FFmpeg as a sub-process:

   ProcessBuilder pb = new ProcessBuilder(command);
  

• Redirect stderr (required for reading FFmpeg messages), without it, the sub-process halts:

   pb.redirectErrorStream(true);
  

• Start FFmpeg sub-process, and create BufferedReader:

   Process process = pb.start();
   BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
  

• Create OutputStream for writing to stdin pipe of FFmpeg sub-process:

   OutputStream writer = process.getOutputStream();
  

• Write raw video frames to stdin pipe of FFmpeg sub-process in a loop:

   byte img[] = new byte[width*height*3];
  
   for (int i = 0; i < n_frmaes; i++)
   {
       //Fill img with pixel data
       ...
       writer.write(img);
   }
  

• Close stdin, read and print stderr content, and wait for sub-process to finish:

   writer.close();
  
   String line;
   while ((line = reader.readLine()) != null)
   {
       System.out.println(line);
   }        
  
   process.waitFor();
  

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Code sample:
The following code sample writes 10 raw video frames with size 192×108 to FFmpeg.
Instead of streaming to RTMP, we are writing the result to test.flv file (for testing).
The example uses hard coded strings and numbers (for simplicity).

Note:
The code sample assume FFmpeg executable is in the execution path.

package myproject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

public class FfmpegVideoWriter {
    public static void main(String[] args) throws IOException, InterruptedException {
        final String rtmp_url = "test.flv"; //Set output file (instead of output URL) for testing.
        
        final String command[] = {"ffmpeg",
                                  "-y",  //Add "-re" for simulated readtime streaming.
                                  "-f", "rawvideo",
                                  "-vcodec", "rawvideo",
                                  "-pix_fmt", "bgr24",
                                  "-s", "192x108",
                                  "-r", "10",
                                  "-i", "pipe:",
                                  "-c:v", "libx264",
                                  "-pix_fmt", "yuv420p",
                                  "-preset", "ultrafast",
                                  "-f", "flv",
                                  rtmp_url};
        
        //https://stackoverflow.com/questions/5483830/process-waitfor-never-returns
        ProcessBuilder pb = new ProcessBuilder(command);    //Create ProcessBuilder
        pb.redirectErrorStream(true); //Redirect stderr
        Process process = pb.start();               
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        
        //Create OutputStream for writing to stdin pipe of FFmpeg sub-process.
        OutputStream writer = process.getOutputStream();
        
        byte img[] = new byte[192*108*3];   //Dummy image 
        
        //Write 10 video frames to stdin pipe of FFmpeg sub-process
        for (int i = 0; i < 10; i++)
        {
            //Fill image with some arbitrary pixel values
            for (int y = 0; y < 108; y++)
            {
                for (int x = 0; x < 192; x++)
                {
                    //Arbitrary RGB values:
                    byte r = (byte)((x * y + i) % 255); //Red component
                    byte g = (byte)((x * y + i*10) % 255); //Green component
                    byte b = (byte)((x * y + i*20) % 255); //Blue component
                    img[(y*192 + x)*3] = b; 
                    img[(y*192 + x)*3+1] = g;
                    img[(y*192 + x)*3+2] = r;
                }
            }
            
            writer.write(img);  //Write img to FFmpeg
        }
        
        writer.close();  //Close stdin pipe.

        //Read and print stderr content
        //Note: there may be cases when FFmpeg keeps printing messages, so it may not be the best solution to empty the buffer only at the end.
        //We may consider adding an argument `-loglevel error` for reducing verbosity.
        String line;
        while ((line = reader.readLine()) != null)
        {
            System.out.println(line);
        }        
       
        process.waitFor();
    }
}

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The code was tested in my PC (with Windows 10), and I am not sure it’s going to work with Android…

The above sample is simplistic and generic, in your case you may use rgba pixel format and write FrameData inside onFrame method.

Sample video frame ("arbitrary pixel values"):

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Update:

The following code sample uses JavaCV – writes Mat data to FFmpeg:

package myproject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.Scalar;
import org.opencv.core.Point;
import org.opencv.imgproc.Imgproc;

public class FfmpegVideoWriter {
    static { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); }
    
    //Build synthetic "raw BGR" image for testing
    public static void buildRawFrame(Mat img, int i)
    {
        int p = img.cols() / 60;    //Used as font size factor.
        img.setTo(new Scalar(60, 60, 60));  //Fill image with dark gray color
        String text = Integer.toString(i+1);
        int font = Imgproc.FONT_HERSHEY_SIMPLEX;
        Point pos = new Point(img.cols()/2-p*10*(text.length()), img.rows()/2+p*10);
        Imgproc.putText(img, text, pos, font, p, new Scalar(255, 30, 30), p*2);  //Blue number
    }
    
    public static void main(String[] args) throws IOException, InterruptedException {
        final int cols = 192;
        final int rows = 108;
        
        final String rtmp_url = "test.flv"; //Set output file (instead of output URL) for testing.
        
        final String command[] = {"ffmpeg",
                                  "-y",  //Add "-re" for simulated readtime streaming.
                                  "-f", "rawvideo",
                                  "-vcodec", "rawvideo",
                                  "-pix_fmt", "bgr24",
                                  "-s", (Integer.toString(cols) + "x" + Integer.toString(rows)),
                                  "-r", "10",
                                  "-i", "pipe:",
                                  "-c:v", "libx264",
                                  "-pix_fmt", "yuv420p",
                                  "-preset", "ultrafast",
                                  "-f", "flv",
                                  rtmp_url};
        
        //https://stackoverflow.com/questions/5483830/process-waitfor-never-returns
        ProcessBuilder pb = new ProcessBuilder(command);    //Create ProcessBuilder
        pb.redirectErrorStream(true); //Redirect stderr
        Process process = pb.start();               
        BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        
        //Create OutputStream for writing to stdin pipe of FFmpeg sub-process.
        OutputStream writer = process.getOutputStream();
        
        //Dummy image (BGR pixel format).
        Mat img = new Mat(rows, cols, CvType.CV_8UC3, Scalar.all(0));
        
        byte buffer[] = new byte[cols*rows*3]; //Byte array for storing img data    
        
        //Write 10 video frames to stdin pipe of FFmpeg sub-process
        for (int i = 0; i < 10; i++)
        {
            buildRawFrame(img, i); //Build image with blue frame counter.
                       
            img.get(0, 0, buffer); //Copy img data to buffer (not sure if this is the best solution).  
            
            writer.write(buffer); //Write buffer (raw video frame as byte array) to FFmpeg
        }
        
        writer.close(); //Close stdin pipe.

        //Read and print stderr content
        String line;
        while ((line = reader.readLine()) != null)
        {
            System.out.println(line);
        }        
       
        process.waitFor();
    }
}

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Sample output frame: