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• FFmpeg cannot extract correct first frame - always extract the second frame [closed]

  21 octobre 2024, par Cai Yu

  I am on macos Ventura 13.2.1, on Macbook Pro M1Max.

  


  The video is number counting animation video. From 2 to 125. The number on first frame is 2. The number on last frame is 125. The number plus one on each frame. You can download the video here.

  


  NOTE that :
First, you hit space bar to play it in Finder, you can see the first frame of the video is number 2.

  


  Second, in professional Video editing software - davinci resolve, on the timeline, you can see the first frame is number 2.

  


  Now I try to use FFmpeg to extract the first frame of the video.
First Try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -vframes 1 /Users/chris/Downloads/1.png


  


  The output png image is number 3. So it's actually the second frame.

  


  Second try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -frames:v 1 /Users/chris/Downloads/1.png


  


  The output png image is still the second frame - the number 3.

  


  Third try :

  


  ffmpeg -i /Users/chris/Downloads/2to125.mov -vf "select=eq(n\,0)" -q:v 3 /Users/chris/Downloads/1.png


  


  The output image is sitll the wrong second frame.

  


  NOTE that :

  


  first : all these three method are from internet. And a lot of people voted correct answer for this question.

  


  second : all their output on my system is the incorrect second frame, not the first frame.

  


  I cannot find what's wrong. Hope friend here help me.

  


• How to use NSProcessInfo's operatingSystemVersion property in place of gestaltSystemVersionMinor and gestaltSystemVersionBugFix

  28 octobre 2016, par Michael Whiteacre

  Newbie here, but longtime frequenter of this essential resource.

  Using :
  MacBook Pro (Retina, 13-inch, Early 2015).
  Processor : 3.1 GHz Intel Core i7
  Memory : 16 GB 1867 MHz DDR3
  Running Yosemite 10.10.5

  I’m attempting to compile my own Perian- and FFmpeg-based FFusion.component (for Quicktime), for 10.11 using Xcode 7.2.1, and in this relatively simple project, as in others, am trying to move away from Gestalt. The original FFusion-RJVB.xcodeproj I’m employing is Xcode-3.2 compatible.

  I have yet to find a clear, definitive solution to what must appear a painfully simple problem to you all. Here is the Gestalt version :
  `

  #if TARGET_OS_MAC
  
  static int GetSystemMinorVersion()
  
  {
  
      static SInt32 minorVersion = -1;
  
      if (minorVersion == -1)
  
          Gestalt(gestaltSystemVersionMinor, &minorVersion);
  
  
  
      return minorVersion;
  
  }
  
  
  
  static int GetSystemMicroVersion()
  
  {
  
      static SInt32 microVersion = -1;
  
      if (microVersion == -1)
  
          Gestalt(gestaltSystemVersionBugFix, &microVersion);
  
  
  
      return microVersion;
  
  }
  
  #endif

  `
  I’ve tried what seems like endless variations of NSProcessInfo i.e.

  ([[NSProcessInfo processInfo] respondsToSelector:@selector(operatingSystemVersion)])

  but I’m afraid I’m not formatting it correctly to achieve my ends. It just hasn’t ’clicked’ in my head yet, so Im hoping someone can give me a push when I see the difference between the gestalt version, my stumbling attempts, and the correct way.

  Many thanks.

• How can I fix choppy ffmpeg RTP streaming over wifi ?

  19 décembre 2015, par awidgery

  I have a Raspberry Pi, with a USB mic and a WiFi dongle dongle connected.

  I’m trying to stream audio only from the Pi, with the intention of receiving the stream over wifi to a custom iOS mobile app using VLCKit. I’m using ffmpeg on the Pi as I need a reasonably low (<2s) latency for this project, and using Icecast/Darkice gave around 15s latency.

  The code executed on the Pi is :

  ffmpeg -f alsa -i plughw:1,0 -acodec libmp3lame -ab 128k -ac 1 -ar 44100  -f rtp rtp://234.5.5.5:1234

  On the Pi end I have a device playing (Christmas !) music constantly into the USB mic for testing purposes. The Pi is only connected by WiFi - not ethernet.

  For testing receiving the stream, I’m using VLC (on a Macbook/iPhone).

  When the Mac is connected through Ethernet, the stream works fine, as you can see here :

  https://goo.gl/photos/HZgNh7z4HgaqHBaP7

  However, when the Mac is connected via WiFi, the stream is choppy, as you can see here :

  https://goo.gl/photos/qjAVH6djqS9Jbvmh6

  You can also see a ping trace from the Mac to the Pi, and the VLC stats. As you can see there doesn’t seem to be a correlation between either of these and the choppiness.

  I’ve tried the VLC iOS app and the choppiness is the same as the Mac on WiFi.

  How can I decrease/remove this chop, even if doing so increases latency a bit ?