Sur d’autres sites (7192)

• CGO : How do you use pointers in Golang to access data from an array in C

  23 avril 2018, par nevernew

  I’m writing an app for the windows platform using FFmpeg and it’s golang wrapper goav, but I’m having trouble understanding how to use the C pointers to gain access to the data array they point to.

  I’m trying to get the data stored in the AVFrame class and use Go to write it to a file, and eventually a texture in OpenGl to make a video player with cool transitions.

  I think understanding how to cast and access the C data will make coding this a lot easier.

  I’ve stripped out all the relevant parts of the C code, the wrapper and my code, shown below :

  C code - libavutil/frame.h

  #include 
  
  
  
  typedef struct AVFrame {
  
  #define AV_NUM_DATA_POINTERS 8
  
      uint8_t *data[AV_NUM_DATA_POINTERS];
  
  }

  Golang goav wrapper - I don’t really know whats going on here with the unsafe.Pointers and casting but it gives me access to the underlying C code

  package avutil
  
  
  
  /*
  
      #cgo pkg-config: libavutil
  
      #include <libavutil></libavutil>frame.h>
  
      #include 
  
  */
  
  import "C"
  
  import (
  
      "unsafe"
  
  )
  
  
  
  type Frame C.struct_AVFrame
  
  
  
  func AvFrameAlloc() *Frame {
  
      return (*Frame)(unsafe.Pointer(C.av_frame_alloc()))
  
  }
  
  
  
  func Data(f *Frame) *uint8 {
  
      return (*uint8)(unsafe.Pointer((*C.uint8_t)(unsafe.Pointer(&amp;f.data))))
  
  }

  My Golang code

  package main
  
  
  
  import "github.com/giorgisio/goav/avutil"
  
  
  
  func main() {
  
      videoFrame := avutil.AvFrameAlloc()
  
  
  
      data := avutil.Data(videoFrame)
  
  
  
      fmt.Println(data) // here i want the values from data[0] to data[7], but how?
  
  }

• How to fix 'ffmpeg server returned 403 forbidden (access denied) ?

  1er février, par peppah

  I'm writing a website to convert youtube videos using NodeJS. I am using a package to convert them (horizon-youtube-mp3). The package works, however, I'm having problems converting. Whenever I try to convert a youtube link, it will return 'server returned 403 forbidden access'. 
This error happens in 95% of the links. Some links actually work and convert correctly, but only a few.

  



  I tried running the script on 3 different computers running 3 different OS's. My VPS, my laptop and my home PC. I looked on the web but couldn't find anything useful.

  



  So yeah, I completely suck since I really don't understand why one video would convert, and the other won't. Even if the region of the video is the same.

  



  Any help would be highly appreciated !

  


• Access pixel data of each frame of a video in Ruby

  23 janvier 2019, par Robin

  I want to be able to read/stream a video with Ruby, on Mac, and be able to get access to the pixel data for each frame.

  What I’ve tried

  • https://github.com/streamio/streamio-ffmpeg

    It’s good at splitting the video into frames, but I don’t know how to get access to the pixel data without saving each frame as an image first (or if it’s possible at all).

  ---

  require 'streamio-ffmpeg'
  
  movie = FFMPEG::Movie.new("flakes.mp4")
  
  
  
  movie.screenshot("screenshots/screenshot_%d.jpg", { custom: %w(-vf crop=60:60:10:10), vframes: (movie.duration).to_i, frame_rate: movie.frame_rate/24 }, { validate: false })`

  ---

  • https://github.com/wedesoft/hornetseye-ffmpeg

    This seemed to have so much potential, but I don’t think it’s maintained anymore, and it’s not meant to be used on MacOS really, so I’m having issues installing it there (headers not found and such, and no way to configure it afaik).

  Any idea what tool or method I could use for this use case ?