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• MP4 libx264 converted to libx265 results in skipped frames

  5 mai 2023, par RGC

  FFmpeg 5-1-2-full_build on Windows10 and storage on windows server 2016.
We have about 1.5 TB data in videos as evidence to document compliance to manufacturing standards.
In a PowerShell batch script I move an libx264 mp4 to a USB3 backup location and then convert it back to the server location it came from :
FFMpeg -i backup\inputFile.mp4 c:v libx265 \server\outputFile.mp4 -n
in order to save much needed space on our server.
It did create a significantly smaller file, but while reviewing the results the length in time is the same as the input but frames seems like they were dropped.

  


  I am stumped as to use what additional parameters as ffmpeg has so many.
Can the fact that it does the conversion over a network to the server be an influence, or the input coming from a USB3 backup drive ?

  


  Thanks for your feedback,
RGC

  


  $noOfFiles++                            # count progress   
$serverMp4 = "$serverLine"          # Server MP4 input address

# Before Conversion grab MP4 from server and move to backup drive
# First grab input file path name and add as destination path, if not exist
$backupMp4 = $serverMp4.Substring(2)
$backupMp4 = "E:\Videos$backupMp4"
$serverLastFolder = (Split-Path $serverLine -Parent)
$serverLastFolder = (Split-Path $serverLastFolder -NoQualifier)
$destinationPath = Join-Path $destinationFolder $serverLastFolder
if(!(Test-Path $destinationPath)) {
    New-Item -ItemType Directory -Path $destinationPath
}

Move-Item -Path $serverMp4 -Destination $destinationPath

$myTime = get-date -format "yyyy-MM-dd HH:mm:ss"        # log Move
$msgOut = "$myTime Moved $serverMp4  to E:\Videos\"
Add-Content -Path $log -Value $msgOut        # store msg in log file
Write-Host $msgOut

# Convert file back to server
ffmpeg -i  $backupMp4 -c:v libx265 $serverMp4 -n

$myTime = get-date -format "yyyy-MM-dd HH:mm:ss"
$msgOut = "$myTime Converted $backupMp4 `n $arrow      $serverMp4"
Write-Host $msgOut                           # Console msg
Add-Content -Path $log -Value $msgOut        # store msg in log file

Write-Host "Completed Move of: $noOfFiles `n $sepLine" -ForegroundColor DarkYellow

# Finished Move of MP4 file to Backup Drive and Converted back to original location. 
# Grab next line  


  


  }

  


• ffmpeg - stretched pixel issue

  5 juin 2023, par Adunato

  Context

  


  I'm converting a PNG sequence into a video using FFMPEG. The images are semi-transparent portraits where the background has been removed digitally.

  


  Issue

  


  The edge pixels of the subject are stretched all the way to the frame border, creating a fully opaque video.

  


  Cause Analysis

  


  The process worked fine in the previous workflow using rembg from command line however, since I started using rembg via python script using alpha_matting to obtain higher quality results, the resulting video has these issues.

  


  The issue is present in both webm format (target) and mp4 (used for testing).

  


  Command Used

  


  Command used for webm is :

  


  ffmpeg -thread_queue_size 64 -framerate 30 -i <png sequence="sequence" location="location"> -c:v libvpx -b:v 0 -crf 18 -pix_fmt yuva420p -auto-alt-ref 0 -c:a libvorbis <png output="output">&#xA;</png></png>

  


  Throubleshooting Steps Taken

  


  

  1. PNG Visual inspection The PNG images have a fully transparent background as desired.

  


  2. PNG Alpha Measurement I have created a couple of python scripts to look at alpha level in pixels and confirmed that there is no subtle alpha level in the background pixels

  


  3. Exported MP4 with AE Using the native AE renderer the resulting MP4/H.265 has a black background, so not showing the stretched pixel issue

  


  


  Image of the Issue

  


  

  


  Sample PNG Image from sequence


  


  Code Context

  


  rembg call via API using alpha_matting seems to generate a premultiplied alpha which uses non black pixels for 0 alpha pixels.

  


  remove(input_data, alpha_matting=True, alpha_matting_foreground_threshold=250,
                    alpha_matting_background_threshold=250, alpha_matting_erode_size=12)


  


  A test using a rough RGB reset of 0-alpha pixels confirms that the images are being played with their RGB value ignoring Alpha.

  


  def reset_alpha_pixels(img):
    # Open the image file
    # Process each pixel
    data = list(img.getdata())
    new_data = []
    for item in data:
        if item[3] == 0:
            new_data.append((0, 0, 0, 0))
        else:
            new_data.append((item[0], item[1], item[2], item[3]))
        # Replace the alpha value but keep the RGB
        

    # Update the image data
    img.putdata(new_data)

    return img


  


  Updates

  


  

  • Added python context to make the question more relevant within SO scope.

  


  


• QML multimedia cannot play m3u8 that is generated with ffmpeg

  5 juin 2023, par LeXela-ED

  With the following command, I am trying to stream an IP camera over web :

  


  ffmpeg -re -i "rtsp://<user>:<password>@<ip>:<port>" -c:v copy -c:a copy -hls_segment_type mpegts -hls_list_size 5 -hls_wrap 5 -hls_time 2 -hls_flags split_by_time -segment_time_delta 1.00 -reset_timestamps 1 -hls_allow_cache 0 -movflags faststart live.m3u8```&#xA;</port></ip></password></user>

  


  This command, produces live.m3u8 and five ts files : live0.ts, live1.ts, live2.ts, live3.ts, and live4. And conversion goes smoothly. At some random point, the content of live.m3u8 is as follows :

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:2
#EXT-X-MEDIA-SEQUENCE:92
#EXTINF:2.000000,
live2.ts
#EXTINF:2.000000,
live3.ts
#EXTINF:2.035800,
live4.ts
#EXTINF:2.000000,
live0.ts
#EXTINF:1.963278,
live1.ts


  


  However, when I tried to play live.m3u8 with the following QML code, it only played a very first segments of it :

  


  import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
import QtQuick.Layouts 1.15
import QtMultimedia 5.15

Window
{
    width: 640
    height: 480
    visible: true

    Item
    {
        anchors.fill: parent

        MediaPlayer
        {
            id: mediaplayer
            source: "path-to-live/live.m3u8"
            videoOutput: videoOutput
        }

        VideoOutput
        {
            id: videoOutput
            anchors.fill: parent
        }

        MouseArea
        {
            anchors.fill: parent
            onPressed: mediaplayer.play();
        }
    }
}



  


  The interesting thing is : I manually deleted live.m3u8, and obviously, ffmpeg generated another one after ! Then I clicked on the QML program window, and surprisingly, it played the stream nonstop as it was expected at the first run !

  


  What is the problem here ? What I am missing ? Should I change the ffmpeg command or do something with my qml code ? Any idea or help ?

  


  Thank you in advance.