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• How to change resolution without compromising video quality using ffmpeg ?

  20 mars 2024, par blake banker

  I'm trying to develop a simple video transcoding system.
When you upload a video,
After extracting the video and audio separately,
I want to encode them at 360, 720, and 1080p resolutions respectively and then merge them to create three final mp4 files.
At this time, I have two questions.

  


  


  1. Is there a big difference between encoding the video and audio separately in the original video file and encoding the original video file as is ? In a related book, it is said that a system is created by separating video and audio, and I am curious as to why.

     


  


  2. I want to change the resolution without compromising the original image quality. At this time, the resolution of the uploaded file can be known at the time of upload. As a test, I created files according to each resolution, and found that the image quality was damaged. If I want to change only the resolution while keeping the original image quality, I would like to know how to adjust each ffmpeg option. We plan to change it to 360, 720, and 1080p.

     


  


  


• Execute my PowerShell script does not work via my C# application

  15 février 2024, par Nixir

  I'm currently working on IP cameras for my job, but I'm just starting out because I've never done anything like this before.
The aim is very simple, to start recording a specific camera via a user action, and to stop the same camera via another user action.
To achieve this, I looked for several solutions and finally decided to use FFMPEG and two Powershell scripts.

  


  The first starts recording using FFMPEG and stores the process PID in a .txt file.

  


  StartRec.ps1

  


  #Paramètres de la caméra IP
$cameraIP = $args[0]
$port = $args[1]
$username = $args[2]
$password = $args[3]

$ipfile = ${cameraIP} -replace "\.", ""
$namefile = "video_"+$ipfile+"_"+(Get-Date -Format "ddMMyyyy_HHmmss") + ".mp4"
$namepidfile = "PID_"+$ipfile+".txt"

# URL du flux vidéo de la caméra (exemple générique, adaptez-le à votre caméra)
$videoStreamUrl = "rtsp://${username}:${password}@${cameraIP}:${port}/videoMain"

# Répertoire de sortie pour la vidéo enregistrée
$outputDirectory = "C:\OutputDirectory"

# Chemin complet du fichier de sortie (nom de fichier avec horodatage actuel)
$outputFile = Join-Path $outputDirectory (${namefile})

# Commande FFmpeg pour enregistrer le flux vidéo en arrière-plan
$ffmpegCommand = "ffmpeg -rtsp_transport tcp -i `"$videoStreamUrl`" -c:v copy `"$outputFile`"" 

# Démarrer FFmpeg en arrière-plan
$process = Start-Process -FilePath "cmd.exe" -ArgumentList "/c $ffmpegCommand" -PassThru

$cheminFichier = Join-Path $outputDirectory $namepidfile

if (-not (Test-Path $cheminFichier)) {
    # Le fichier n'existe pas, créer le fichier
    New-Item -ItemType File -Path $cheminFichier -Force
    Write-Host "Fichier créé : $cheminFichier"
} else {
    Write-Host "Le fichier existe déjà : $cheminFichier"
}

Start-Sleep -Seconds 5

$processId = Get-WmiObject Win32_Process -Filter "Name='ffmpeg.exe'" | Select-Object -ExpandProperty ProcessId

# Enregistrez le PID dans un fichier
$process.Id | Out-File $cheminFichier

Write-Host "Enregistrement démarré. PID du processus : $($processId)"


  


  The second reads the contents of this .txt file, stores it in a variable as a PID and stops the process via its Id, then closes the command window associated with this process (which tells the camera that the recording is finished).

  


  StoptRec.ps1

  


  $cameraIP = $args[0]
$ipfile = ${cameraIP} -replace "\.", ""
$namepidfile = "PID_"+$ipfile+".txt"
$outputDirectory = "C:\OutputDirectory"
$cheminFichier = Join-Path $outputDirectory $namepidfile

$pidcontent = Get-Content $cheminFichier -Raw 
if (-not $pidContent) {
    Write-Host "Erreur : Le fichier PID est vide. Assurez-vous que l'enregistrement est démarré."
    exit
}

$processId  = $pidContent.Trim() -as [int]

if (-not $processId) {
    Write-Host "Erreur : Impossible de convertir le contenu du fichier PID en entier."
    exit
}

Get-Process -Id $processId

Stop-Process -Id $processId -PassThru | Foreach-Object { $_.CloseMainWindow() }

Write-Host "Enregistrement arrêté pour le processus PID $processId"
Start-Sleep -Seconds 15


  


  The problem is that they work, except in one case that I'll explain :
First, I tried to run them via PowerShell, the recording starts up and the script works as expected, as does the shutdown. My final file is usable.
I then performed C# actions in my Controller, which calls and executes these scripts :

  


  The action that calls StartRec.ps1

  


          public void startRecordingCam1(string ipAddress)
        {
            string ps1File = @"C:\OutputDirectory\StartRec.ps1";
            string cameraIP = "Camera IP Adress";
            string port = "88";
            string username = "Username";
            string password = "Password";

            Process process = Process.Start(new ProcessStartInfo
            {
                FileName = "powershell.exe",
                Arguments = $"-NoProfile -ExecutionPolicy Bypass -File \"{ps1File}\" \"{cameraIP}\" \"{port}\" \"{username}\" \"{password}\"",
                UseShellExecute = false,
                RedirectStandardInput = true
                //CreateNoWindow = true
            });
        }


  


  The action that calls StopRec.ps1

  


         public void stopRecording(string ipAddress)
        {
            string ps1File = @"C:\Projet Valentin\CameraTest\StopRec_Csharp.ps1";
            string cameraIP = "10.0.1.10";

            ProcessStartInfo startInfo = new ProcessStartInfo()
            {
                FileName = "powershell.exe",
                Arguments = $"-NoProfile -ExecutionPolicy ByPass -File \"{ps1File}\" \"{cameraIP}\" ",
                UseShellExecute = true
            };
            Process.Start(startInfo);
        }


  


  When I run the two scripts via these actions, StartRec.ps1 works well, but StopRec.ps1 doesn't work completely : the process is stopped, but the command window isn't closed, so camera recording continues (despite the end of the process).
As both scripts worked perfectly when launched with Powershell, but not with the C# application, I tried several combinations of "Start-Stop" with "PowerShell/C#".

  


  If I run StartRec.PS1 with the C# application and StopRec.PS1 with PowerShell, it works.
If I run StartRec.PS1 with PowerShell and StopRec.PS1 with the C# application, it works.
If I run StartRec.PS1 with PowerShell and StopRec.PS1 with PowerShell, it works.
The only case that doesn't work is when I run both via the C# application

  


  One thing I can add that I discovered while debugging is that this :
Stop-Process -Id $processId -PassThru | Foreach-Object { $_.CloseMainWindow() }

  


  Returns false in the only case where it doesn't work, and true in all other cases

  


  That's all the details I can give you, thanks for your help !

  


• avcodec/libjxl.h : include version.h

  23 janvier 2024, par Leo Izen

  avcodec/libjxl.h : include version.h
  This file has been exported since our minimum required version (0.7.0),
  
  but it wasn't documented. Instead it was transitively included by
  
  <jxl/decode.h> (but not jxl/encode.h), which ffmpeg relied on.
  libjxl broke its API in libjxl/libjxl@66b959239355aef5255 by removing
  
  the transitive include of version.h, and they do not plan on adding
  
  it back. Instead they are choosing to leave the API backwards-
  
  incompatible with downstream callers written for some fairly recent
  
  versions of their API.
  As a result, we include <jxl/version.h> to continue to build against
  
  more recent versions of libjxl. The version macros removed are also
  
  present in that file, so we no longer need to redefine them.
  Signed-off-by : Leo Izen <leo.izen@gmail.com>
  

  • [DH] libavcodec/libjxl.h