Recherche avancée

Sur d’autres sites (7045)

• Image generated by System.Drawing.Image is 10x larger than original file

  13 mai 2021, par Ninbura

  I've written a Powershell script that extracts one frame from a dshow capture device using FFmpeg, and then copies the output image from a file to my clipboard :

  


  $screenshot = [System.Drawing.Image]::FromFile((Get-Item -Path $outputFilePath))
[System.Windows.Forms.Clipboard]::SetImage($screenshot)
$screenshot.Dispose()


  


  The original file is a 1MB JPEG, but the image in my clipboard is an 11MB PNG. When I go to paste this file into something like Discord the file size is too large, unless you have Discord Nitro.

  


  Is there any way to avoid this file size inflation while using [System.Drawing.Image]::FromFile() ?

  


  Here's an easy test template :

  


  Add-Type -AssemblyName System.Drawing
Add-Type -AssemblyName System.Windows.Forms

$screenshot = [System.Drawing.Image]::FromFile((Get-Item -Path "Path to picture"))
[System.Windows.Forms.Clipboard]::SetImage($screenshot)
$screenshot.Dispose()


  


  Edit 2021/05/13 :

  


  Interestingly, it's starting to seem like this is a limitation of copying an image to a clipboard. I decided to dig deeper and see if the image size was increasing when I drew the image with System.Drawing.Image or when I pushed it in my clipboard with System.Windwos.Forms.Clipboard. If I save the image before putting it my clipboard like so, it retains the original file size, even if I change the extension to png :

  


  Add-Type -AssemblyName System.Drawing
Add-Type -AssemblyName System.Windows.Forms

$screenshot = [System.Drawing.Image]::FromFile((Get-Item -Path "C:\Users\gabri\Pictures\FFScreenshots\2021-05-12 19-04-26.845.jpeg"))
$screenshot.Save("C:\Users\gabri\Pictures\FFScreenshots\test.jpeg") # test.png makes no difference
$screenshot.Dispose()


  


  So it would seem that the image grows exponentially in size specifically when I push it to my clipboard. I verified this by simply uploading an image to Discord, copying it to my clipboard (click image > Open original > right click and copy result), and uploading it again. Sure enough, the new image pasted from my clipboard was around 10x the size of the original image (1MB vs 12MB). I wondered if this was a "limitation" of Windows so I ran the same test on Ubuntu 20.04. Uploaded an image to Discord, copied the image to my clipboard, and uploaded it again. Once again the image was about 10x larger, though slightly smaller than then when I uploaded the image from my clipboard on my Windows machine (11.4MB VS 12MB). Just to make sure this wasn't limited to Discord, I ran the same test with Gmail in-browser on both operating systems, same result.

  


  Alas, there appears to be something happening when you copy an image to a clipboard that drastically increases file size. One thing's for sure, whatever's happening is definitely over my head.

  


• avformat/mxfdec : Don't use wrong type of pointer

  12 mars 2021, par Andreas Rheinhardt

  avformat/mxfdec : Don't use wrong type of pointer
  If one of the two results of a ternary conditional is a pointer to void,
  
  the type of the whole conditional operator is a pointer to void, even
  
  when the other possible result is not a pointer to void. This loophole
  
  in the type system has allowed mxf_read_local_tags to have a pointer of
  
  type pointer to MXFMetadataSet that actually points to an MXFContext.
  Reviewed-by : Tomas Härdin <tjoppen@acc.umu.se>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/mxfdec.c

• Is there a way to find out whether ffmpeg is performing optimally in my system using a ffmpeg command of sorts ?

  17 octobre 2020, par Aspiring Dev

  I'm encoding a file (mediainfo below) using the following command :

  


  ffmpeg -i AHomeMovie.mkv -map 0 -c copy -c:v libx264 -preset veryslow -crf 17 -c:a aac -b:a 256k -threads 8 resultdir/AHomeMovie.mkv


  


  And getting more or less the following performance after a couple of minutes :

  


  frame= 2036 fps=2.5 q=22.0 size=   87535kB time=00:01:25.25 bitrate=8411.2kbits/s speed=0.104x    


  


  Is this normal performance for a laptop with a i7-8550U, 16gb of RAM, UHD graphics 620 running Linux ? Is there a way to find out whether ffmpeg is performing optimally using a ffmpeg command of sorts ? I know it's commodity hardware by now but I just want to get some perspective on how the system is performing. I'm aware that I can use a different -preset speed btw.

  


  Mediainfo :

  


  General
Unique ID                                : 25145236523685421256398752247554522365 (0x14258745965823652446224452555874)
Complete name                            : AHomeMovie.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 6.35 GiB
Duration                                 : 22 min 47 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 39.9 Mb/s
Movie name                               : A Home Movie
Encoded date                             : UTC 2020-09-10 22:10:12
Writing application                      : mkvmerge v42.0.0 ('Overtime') 64-bit
Writing library                          : libebml v1.3.10 + libmatroska v1.5.2

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 22 min 45 s
Bit rate mode                            : Variable
Bit rate                                 : 38.0 Mb/s
Maximum bit rate                         : 40.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.764
Stream size                              : 6.04 GiB (95%)
Default                                  : Yes
Forced                                   : No

Audio #1
ID                                       : 2
Format                                   : FLAC
Format/Info                              : Free Lossless Audio Codec
Codec ID                                 : A_FLAC
Duration                                 : 22 min 45 s
Bit rate mode                            : Variable
Bit rate                                 : 614 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 11.719 FPS (4096 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossless
Stream size                              : 100 MiB (2%)
Writing library                          : libFLAC 1.2.1 (UTC 2007-09-17)
Language                                 : Japanese
Default                                  : Yes
Forced                                   : No

Audio #2
ID                                       : 3
Format                                   : FLAC
Format/Info                              : Free Lossless Audio Codec
Codec ID                                 : A_FLAC
Duration                                 : 22 min 46 s
Bit rate mode                            : Variable
Bit rate                                 : 1 317 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 11.719 FPS (4096 SPF)
Bit depth                                : 24 bits
Compression mode                         : Lossless
Delay relative to video                  : 24 ms
Stream size                              : 215 MiB (3%)
Writing library                          : libFLAC 1.2.1 (UTC 2007-09-17)
Language                                 : English
Default                                  : No
Forced                                   : No