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• How to calculate the "Range" header for mp4 file to play/download a part of it ? [youtube-dl]

  5 décembre 2016, par supersan

  I’m using youtube-dl to download videos from YouTube. Unfortunately, sometimes I just need to download a part of the video like 10 seconds of a 3 hour video and here is how I see I can do it.

  Step 1 : Get the URL of the mp4 file from youtube-dl.

  youtube-dl -g -f "[ext=mp4]" https://www.youtube.com/watch?v=qOZ1u9VpoMk

  This returns $url : the full URL of mp4 file on server.

  Step 2 : Download part of the video using curl

  curl -r $startBytes-$endBytes $url

  But how to calculate $startBytes and $endBytes. What is the formula for that ?

  P.S I was thinking could be something as simple but this isn’t it..

  $startBytes = (total_size_of_video / total_length_of_video_secs) * start_seconds

  P.P.S. When I play the mp4 video in Chrome and use the scrub bar to jump around in the video, Chrome too send the Range header to the same URL (as I can see in fiddler)

• ffmpeg crop and watermark in a single step

  11 juin 2018, par rbarab

  We are processing short videos. Most of them are 640x480, recorded by mobile. Many of them have a black frame on left and right.
  I would like to watermark the videos and currently using this command.

  ffmpeg -i IN.mp4 -i WATERMARK.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" OUT.mp4

  The problem is that if there is a frame, part of the watermark goes on the frame and only a part is on the actual content. Would like to place the watermark on the bottom right of the actual content.

  Are any of these possible, or any other ideas ?

  a, Dynamically detect the black frames and adjust the watermark position accordingly.

  b, Crop the black frame and watermark the content correctly in the same step.

  Thanks a lot for your help !

  EDIT :

  I have found that it won’t be possible in one step.

  1, I can get the crop size

  ffmpeg -i INPUT.mp4 -t 2 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1

  2, Then crop the video

  ffmpeg -i INPUT.mp4 -filter:v "crop=352:480:144:0" -c:a copy OUTPUT.mp4

  3, Then watermark it

  ffmpeg -i INPUT VIDEO.mp4 -i INPUT IMAGE.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" OUTPUT VIDEO.mp4

  Is there a way to merge 2, and 3, into a single step ?

• ProcessBuilder is not called when trying to start a process

  15 juin 2022, par xnok

  I am trying to understand more about the ffmpeg usage in JavaCV for android studio and for said task I am trying to use ProcessBuilder. I tried writting a simple program to debug the pb.start(); Although, I am not getting a response. What I did was to start a default/empty activity and pasted the following program :

  


  package com.example.myapplication;

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

import org.bytedeco.javacpp.Loader;

import android.os.Build;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {
    static final int cols = 192;
    static final int rows = 108;
    static final String ffmpeg = Loader.load(org.bytedeco.ffmpeg.ffmpeg.class);
    static final String rtmp_url = "test.flv";
    static final String[] command = {ffmpeg,
            "-y",
            "-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};
    @RequiresApi(api = Build.VERSION_CODES.O)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new Thread(t1).start();

    }
    private static Runnable t1 = () -> {
        Log.e("TAG", "void OnCreate called successfully!");
        ProcessBuilder pb = new ProcessBuilder(command).redirectErrorStream(true);
        pb.redirectErrorStream(true);
        try {
            Process process = pb.start();
            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            OutputStream writer = process.getOutputStream();
            Log.e("TAG", "Something good happened here");
        } catch (IOException e) {
            e.printStackTrace();
            Log.e("TAG", "Nothing good happened here");
        }
    };


}


  


  My current problem is that I can't seem to start properly the processBuilder process via pb.start() ;

  


  I get the following logs from the logcat panel :

  


  2022-06-14 17:24:46.328 13371-13371/com.example.myapplication E/TAG: void OnCreate called successfully!
2022-06-14 17:24:46.333 13371-13371/com.example.myapplication E/TAG: Nothing good happened here


  


  I'd like to understand why is it skipping the try/catch block and not starting the process ?

  


  EDIT : I made some changes as per @g00se's suggestions and I got the following stack trace from the code above :

  


  2022-06-15 00:32:26.700 29787-29787/? E/USNET: USNET: appName: com.example.myapplication
2022-06-15 00:32:29.328 29787-29828/com.example.myapplication E/TAG: void OnCreate called successfully!
2022-06-15 00:32:29.330 29787-29828/com.example.myapplication E/AndroidRuntime: FATAL EXCEPTION: Thread-4
    Process: com.example.myapplication, PID: 29787
    java.lang.NullPointerException
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
        at com.example.myapplication.MainActivity.lambda$static$0(MainActivity.java:48)
        at com.example.myapplication.MainActivity$$ExternalSyntheticLambda0.run(Unknown Source:0)
        at java.lang.Thread.run(Thread.java:920)