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• ffmpeg how to extract X frames every Y interval from url efficiently

  13 décembre 2018, par Luay Gharzeddine

  I’m trying to gather data for a datascience project, and am downloading frames from online videos using ffmpeg. I want to download a subset of the frames in the video, without needing to be precise about which, the only requirement is that they are reasonably spaced apart from each other.

  I have tried

  ffmpeg -i "http://www.somevideo.com" -r 1 -f image2 "image%06d.jpg"

  and

  ffmpeg -i "http://www.somevideo.com" -vf fps=1 "image%06d.jpg"

  and eventually found the following method

  ffmpeg -ss offset1 -i "http://www.somevideo.com" -ss offset2 -i "http://www.somevideo.com" -map 0:v -frames:v 10 -start_number 0 "image%06d.jpg" -map 1:v -frames:v 10 -start_number 10 "image%06d.jpg"

  and all work, but are slow. I have found a hack where I run the following command multiple times, at different offsets, and it seems to be the fastest (where each ffmpeg command is run in parallel multithreaded)

  ffmpeg -ss offset -i "http://www.somevideo.com" -vframes frames_per_fragment -an -start_number start_index "image%06d.jpg"

  this about 25% faster than the previous method

  Is there a faster way to do this ? The issue is that downloading over a network is a bottleneck, so I want to download only the frames I need. I’m looking to download videos/frames in bulk, so any speed improvement would be helpful.

• stream a video file using srt protocol [closed]

  13 novembre 2022, par programmer

  I want to stream a file over the network from a server. I will need to
send the AVFormatContext, and individual AVPackets over the network.For this reason i use libav library(ffmpeg) and srt protocol to send to specific port. But i can not find a function that send avpackets in srt. I find srt_sendmsg() function but it is not usable in this case.Does it have any solution ?
thanks in advance.

  


  As i say i want to design a srt server that streams specific file. it should read the video file and then send it on specific port that clients can connect to that and receive live stream.I want to use c++ programming , libav libraray and srt protocol

  


• G.I. Joe Custom Multimedia

  30 mars 2012, par Multimedia Mike — General

  I received this 3-disc set of G.I. Joe CD-ROMs today :

  
  
  

  Copyright 2003, and labeled as PC ONLY. Each disc claims to have 2 episodes. So are these some sort of video discs ? Any gaming elements ? I dove in to investigate.

  So, it turns out that there are some games on these discs, done in Flash Player (which tells me that these were probably available on the web at some point). Here’s a shooting gallery game from the first disc :

  
  
  

  As promised by the CD-ROM copy, the menu does grant access to 2 classic G.I. Joe episodes. Selecting either one launches this :

  
  
  

  Powered by C-ezy ? Am I interpreting that correctly ? Anyway, the video player goes fullscreen and looks fine (given the source material). I can’t capture screenshots and controls are limited to : space for pause, ESC to exit player, and up/down to control volume. No seeking and certainly no onscreen controls. Pretty awful player.

  Studying the first disc, I find a 550 MB file with the name 5859Hasbro.egm. Coupled with ep58.cfg and ep59.cfg files in the same directory, I gather that the disc has G.I. Joe episodes 58 and 59 (though the exact episodes, “There’s No Place Like Springfield” parts 1 and 2, are listed on Wikipedia as being episodes 154 and 155 ; but who’s counting ?). The cfg files contain this text :

  ep58.cfg :
  EGM_GIJOE.exe
  5859Hasbro.egm /noend /track:0 /singletrack
  ep59.cfg :
  
  EGM_GIJOE.exe
  
  5859Hasbro.egm /noend /track:1 /singletrack
  

  The big EGM file starts with the string “Egenie Player”. After that, I see absolutely no clues. The supporting EGM_GIJOE.exe file has some interesting strings : “Decore Bits Per Pixel” (I know I have seen “Decore” used to mean “decoding core” in some libraries), “Egenie Player – %s, Version :%s”, “4th June 2002″, a list of common FourCC tags seen in AVI files, “Brought to you by Martin, Patrick Bob and Bren” (do you suppose “Patrick Bob” is one person’s name ?), a list of command line options…

  Aha ! A URL : http:\www.e-genie.tv (yep, backslashes, not forward slashes). e-genie.tv seems to redirect to mygenie.tv, which… doesn’t appear to be strictly related to video technology these days.