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• Ramp- Slow Motion in IOS

  26 juin 2013, par 2vision2

  I have to do "ramp-slow motion" in a video file along with audio, in-between some frames and need to store the ramped video as a new video.

  Ref : http://www.youtube.com/watch?v=BJ3_xMGzauk (watch from 0 to 10s)

  From my analysis, I've found that AVFoundation framework can be helpful.

  Ref :
  http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/00_Introduction.html

  Copy and pasted from the above link :

  "
  Editing
  AV Foundation uses compositions to create new assets from existing pieces of media (typically, one or more video and audio tracks). You use a mutable composition to add and remove tracks, and adjust their temporal orderings. You can also set the relative volumes and ramping of audio tracks ; and set the opacity, and opacity ramps, of video tracks. A composition is an assemblage of pieces of media held in memory. When you export a composition using an export session, it's collapsed to a file.
  On iOS 4.1 and later, you can also create an asset from media such as sample buffers or still images using an asset writer.

  "

  Questions :
  Can I "ramp-slow mote" the video/audio file using the AVFoundation framework ? Or Is there any other package available ? If i want to handle audio and video separately, please guide me how to do ?

• How to stream cv2.VideoWriter frames to and RTSP server

  10 juin 2022, par chasez0r

  Environment : Docker, Ubuntu 20.04, OpenCV 3.5.4, FFmpeg 4.2.4

  


  Im currently reading the output of a cv2.VideoCapture session using the CV_FFMPEG backend and successfully writing that back out in real time to a file using cv2.VideoWriter. The reason I am doing this is to drawing bounding boxes on the input and saving it to a new output.

  


  The problem is I am doing this in a headless environment (Docker container). And I’d like to view what's being written to cv2.VideoWriter in realtime.

  


  I know there are ways to pass my display through using XQuartz for example so I could use cv2.imshow. But what I really want to do is write those frames to an RTSP Server. So not only my host can "watch" but also other hosts could watch too.

  


  After the video is released I can easily stream the video to my RTSP Server using this command.

  


  ffmpeg -re -stream_loop -1 -i output.mp4 -c copy -f rtsp rtsp://rtsp_server_host:8554/stream

  


  Is there anyway to pipe the frames as they come in to the above command ? Can cv2.VideoWriter itself write frames to an RTSP Server ?

  


  Any ideas would be much appreciated ! Thank you.

  


• ffmpeg Grab Single Frame From Youtube Stream

  11 septembre 2021, par Rich_F

  I'm trying to grab a single frame of a streaming video on Youtube.

  


  This is an example

  


  This is the code structure I'm trying to use :

  


  ffmpeg --verbose -i $(youtube-dl -f 96 --no-playlist 'https://www.youtube.com/watch?v=XMs6LnT5mfk') -frames:1 -pred 1 clip1.jpg


  


  Trying to use youtube-dl to grab part of a stream, doesn't seem to work, and is actually throwing an ffmpeg error at me :

  


  [youtube] Q-44KECp-xQ: Downloading webpage
[youtube] Downloading just video Q-44KECp-xQ because of --no-playlist
[youtube] Q-44KECp-xQ: Downloading m3u8 information
[youtube] Q-44KECp-xQ: Downloading MPD manifest
[download] Destination: Ryde Esplanade & Pier, Isle of Wight UK _ Railcam LIVE 2021-09-11 03_25-Q-44KECp-xQ.mp4

ERROR: ffmpeg exited with code -9


  


  How can I achieve this ? I'm open to reworking this approach, or moving to something completely different. Cheers