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• Imagemagick & Pillow generate malformed GIF frames

  1er juin 2016, par RiTu

  I need to extract the middle frame of a gif animation.

  Imagemagick :

  convert C:\temp\orig.gif -coalesce C:\temp\frame.jpg

  generates the frames properly :

  

  However when I extract a single frame :

  convert C:\temp\orig.gif[4] -coalesce C:\temp\frame.jpg

  then the frame is malformed, as if the -coalesce option was ignored :

  

  Extraction of individual frames with Pillow and ffmpeg also results in malformed frames, tested on a couple of gifs.

  Download gif : https://i.imgur.com/Aus8JpT.gif

  I need to be able to extract middle frames of every gif version in either PIL, Imagemagick of ffmpeg (ideally PIL).

• Extract frames as images from an RTMP stream in real-time

  7 novembre 2014, par SoftForge

  I am streaming short videos (4 or 5 seconds) encoded in H264 at 15 fps in VGA quality from different clients to a server using RTMP which produced an FLV file. I need to analyse the frames from the video as images as soon as possible so I need the frames to be written as PNG images as they are received.

  Currently I use Wowza to receive the streams and I have tried using the transcoder API to access the individual frames and write them to PNGs. This partially works but there is about a second delay before the transcoder starts processing and when the stream ends Wowza flushes its buffers causing the last second not to get transcoded meaning I can lose the last 25% of the video frames. I have tried to find a workaround but Wowza say that it is not possible to prevent the buffer getting flushed. It is also not the ideal solution because there is a 1 second delay before I start getting frames and I have to re-encode the video when using the transcoder which is computationally expensive and unnecessarily for my needs.

  I have also tried piping a video in real-time to FFmpeg and getting it to produce the PNG images but unfortunately it waits until it receives the entire video before producing the PNG frames.

  How can I extract all of the frames from the stream as close to real-time as possible ? I don’t mind what language or technology is used as long as it can run on a Linux server. I would be happy to use FFmpeg if I can find a way to get it to write the images while it is still receiving the video or even Wowza if I can find a way not to lose frames and not to re-encode.

  Thanks for any help or suggestions.

• Solid FFMPEG in background worker fails on user pc

  17 février 2015, par jon783

  I’m using Solid FFPEG to rip out individual frames from a video, I’m using this to ’play’ the video (so it rips out each frame). I’m using a background worker to keep the UI responsive. Running on my PC I have no problems, but on the test PC it will not display the frames, I get the below error from the background workers RunWorkerCompleted method.

  System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'CAVEditLib.ICAVConverter'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{59C19DEF-02ED-44CD-BFD8-2FD09DBDC9F9}' failed due to the following error: Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY)) at System.StubHelpers.StubHelpers.GetCOMIPFromRCW(Object objSrc, IntPtr pCPCMD, IntPtr& ppTarget, Boolean& pfNeedsRelease)
  
     at CAVEditLib.ICAVConverter.get_AVPrope()
  
     at RoutePlotter.VideoManager.UpdateAllFrames(Decimal frontNumericValue, Decimal backNumericValue, Decimal leftNumericValue, Decimal rightNumericValue)
  
     at RoutePlotter.MainForm.backgroundWorker_DoWork(Object sender, DoWorkEventArgs e)
  
     at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
  
     at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)

  The cavEditLib.dll file seems to be registered on the Test PC, but the background worker won’t work.

  Thanks fro any help.