Recherche avancée

Sur d’autres sites (6702)

• FFmpeg Video Library Quick Review

  3 juillet 2019, par Rich_F

  I’m in need of reducing 18 videos so I can review them daily. I’d like to script some kind of compression or sampling using FFmpeg to not have to sit through 6 hours of video every day.

  What is the best way to review 6 hours of videos captured every day on SD cards ? The videos come in two cards, a 32 GB card ( 4 hours) and a 16 GB card ( 2 hours).

  Currently, I’m concatenating all videos and creating a screenshot every 3 seconds, which seems the longest I can go without missing something in the field of view (a vehicle will enter/leave). Still, this is thousands of images per card, and I select all, then preview and scroll down using page up/down. Any vehicle quickly appears in the thumbnails. This system isn’t bad, but I’m always inquisitive. I’m looking for more ways of sampling or seeing if any motion detection or frame analysis might register where I should be looking in my library of original captured videos.

  Options :

  1. Motion capture by analysis of frame by frame through trial and error on sensitivity to not measure wind on the bushes. This could be output to filename and time within the video (videos are captured 10 minutes long).

  2. Take my exported list of png files and string them together somehow into a slide show.

  3. Version 1 here, plus some retroactive capture of clips inside master clips.

  4. Some kind of compression. Again, I have to respect the 3-second max jump.

  Any other options that would be relatively easy to achieve without moving into any other software ? I’m trying to put the heavy lifting on the computer, as staring at videos is not something I’m finding I’ll be able to do for many days.

• How to create a timelapse directly to MP4 with FFMPEG by adding JPEG image data every N seconds ?

  28 août 2019, par suromark

  I am trying to create a bash script with FFMPEG on an OctoPi 3d printer controller that periodically appends new frames to an MP4 timelapse output on the fly (e.g. compress/add one frame every N seconds instead of once the print is finished, processing a folder with hundreds or thousands of images, to spread the required video calculations over the whole print time where the Raspberry Pi is mostly idle anyway).

  I’d like to reduce the storage overhead for the JPEG files and the delay upon finish.

  So far I’ve set up a bash script that starts on boot (via rc.local), then monitors the Octoprint API for signs of activity every 5 seconds (while true ... sleep(5) ) with a second watchdog script. Once the progress value is non-false, and the print head temperature is above 120 °C, the script polls the localhost URL of the webcam for a JPEG file that is timestamped and stored in a folder with the current print job’s name (taken from the API). Once the print is completed, I scp the files to my laptop where I use FFMPEG to convert them to MP4.

  Ideally I’d like to keep the monitoring script behaving as it does, but instead of writing out JPEGs I’d like to pipe the data into FFMPEG (once every N seconds) upon which FFMPEG should process it as new single frame of its stream-in-progress, writing out the data once a new GOP is complete (or finish the last GOP in the buffer once a kill signal arrives).

  For this I most likely need to start FFMPEG from the main loop once a new job starts (to set the output file) then establish some pipe structure to send the JPEG frames, I guess ?

  So far I’ve not managed to find/google any example for this (or a similar workflow), though I think it’s not that exotic an use case...?

  Edit to add :
  This is my current FFMPEG bash command :

  ffmpeg \
  
  -framerate 30 \
  
  -pattern_type glob \
  
  -i '*.jpg' \
  
  -c:v libx264 \
  
  -vf "normalize=blackpt=black:whitept=white:smoothing=50" \
  
  -pix_fmt yuv420p \
  
  ../"$outname""$outdate"_lapse.mp4

  So far, I’ve managed to get FFMPEG to read from a named pipe, but it saves the output and stops after the first frame is through the pipe. I’d like to tell it to keep reading/waiting from the pipe until it receives a kill (or other) signal :

  mkfifo /tmp/testpipe
  
  
  
  ffmpeg -y -framerate 30 -pattern_type glob -f image2pipe -i /tmp/testpipe -c:v libx264 -pix_fmt yuv420p "pipetestout.mp4"

  and from another terminal :

  cat some-image.jpg > /tmp/testpipe

  I think I’m close (but no cigar yet) ...

• What's the best way to get video metadata from a MP4 file in ASP.Net MVC using C# ?

  23 septembre 2019, par Maddhacker24

  I’ve been searching on Google and StackOverflow for a good couple of hours. There seems to be a lot of similar questions on StackOverflow but they are all about 3-5 years old.

  Is using FFMPEG still the best way these days to pull metadata from a video file in a .NET web application ? And if so, what’s the best C# wrapper out there ?

  I’ve tried MediaToolkit, MediaFile.dll without any luck. I saw ffmpeg-csharpe but that looks like it hasn’t been touched in a few years.

  I haven’t found any current data on this subject. Is the ability to pull metadata from a video built into the latest version of .NET now ?

  I’m basically looking for any direction at this point.

  I should add that whatever I use could be invoked thousands of times per hour so it will need to be efficient.