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• ffpmeg - how to detect if video crop is completed ?

  30 septembre 2021, par Radespy

  Thanks in advance.

  


  I'm trying to crop a .mp4 video using an ffmpeg binary (within the context of an electron-react-app).

  


  (The binary is run in a child process using execFile() and outputs to a temp folder which is later deleted)

  


  ffmpeg varies considerably in the time it takes to complete the creation of a cropped video file (1sec to 18sec) depending on the computer (mac vs Windows).

  


  I need to read the cropped video file.

  


  I've set up an event listener in the Main process of electron

  


  
if (!monitorCroppedFile) {
        console.log(`${croppedFilePath} doesn't exist`);
      } else {
        console.log(`${croppedFilePath} exists !`)
        ...readFile...;


  


  Once monitorCroppedFile = true I read it using fs.readfile().

  


  The problem is that ffmpeg initally creates the cropped file path but it sometimes takes ages to complete the process of cropping.

  


  This results in the read file often being blank (as the read is triggered on detecting the file path of the cropped file).

  


  I've tried using -preset ultrafast in the ffmpeg arguments but this only improves things on Windows marginally.

  


  The problem doesn't occur on Macs.

  


  Can anybody suggest a possible solution ? Is there a way to detect when the crop is fully completed ?

  


  Many thanks.

  


• Merge Audio and Video using ffmpeg - Python Lib [duplicate]

  15 janvier 2021, par badr

  i have tried

  


  import ffmpeg
video = ffmpeg.input('video.mp4')
audio = ffmpeg.input('audio.mp3')
ffmpeg.merge_outputs(video, audio).run()


  


  and it returns

  


  TypeError: Expected incoming stream(s) to be of one of the following types: ffmpeg.nodes.OutputStream; got <class>&#xA;</class>

  


  and i have tried

  


  import ffmpeg
video = ffmpeg.input('video.mp4')
audio = ffmpeg.input('audio.mp3')
ffmpeg.concat(video, audio, v=1, a=1).output('finished_video.mp4').run()


  


  and it returns

  


  FileNotFoundError: [WinError 2] The system cannot find the file specified


  


  also i did try

  


  import subprocess    
subprocess.run("ffmpeg -i video.mp4 -i audio.mp3 -c copy output.mp4")


  


  and it returns

  


  'ffmpeg' is not recognized as an internal or external command


  


  how can i do it right ?

  


• How to estimate bandwidth / speed requirements for real-time streaming video ?

  19 juin 2016, par Vivek Seth

  For a project I’m working on, I’m trying to stream video to an iPhone through its headphone jack. My estimated bitrate is about 200kbps (If i’m wrong about this, please ignore that).

  I’d like to squeeze as much performance out of this bitrate as possible and sound is not important for me, only video. My understanding is that to stream a a real-time video I will need to encode it with some codec on-the-fly and send compressed frames to the iPhone for it to decode and render. Based on my research, it seems that H.265 is one of the most space efficient codecs available so i’m considering using that.

  Assuming my basic understanding of live streaming is correct, how would I estimate the FPS I could achieve for a given resolution using the H.265 codec ?

  The best solution I can think of it to take a video file, encode it with H.265 and trim it to 1 minute of length to see how large the file is. The issue I see with this approach is that I think my calculations would include some overhead from the video container format (AVI, MKV, etc) and from the audio channels that I don’t care about.