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• How to encode a series of .dpx files using X264

  4 juin 2015, par user3759710

  I am complete newbie to video encoding. I am trying to encode a series of .dpx files into one single encoded video O/P file in any of the following format. ( .mp4,.avi,.h264,.mkv etc)

  I have tried 2 different approaches. The first one works and the second one does not.
  I would like to know the difference between the two. Any help / input would be much appreciated.

  1) using FFMPEG along with x264 library and it works well. I am able to produce desired output

  ffmpeg -start_number 0 -i frame%4d.dpx -pix_fmt yuv420p -c:v libx264 -crf 28 
  
  -profile:v baseline fromdpx.h264

  2) I first try to concatenate all the dpx files into a single file using concate protocol in ffmpeg and then use x264 to encode the concatenated file.
  Here I see that the size of the concatenated file is the sum of all the files concatenated. But when I use x264 command to encode the concatenated file, I get a green screen (basically not the desired output) .

  ffmpeg -i "concat:frame0.dpx|frame01.dpx|frame2.dpx etc" -c copy output.dpx

  then

  x264 --crf 28 --profile baseline -o encoded.mp4 --input-res 1920x1080 --demuxer raw 
  
  output.dpx

  I also tried to encoded the concatenated file using ffmpeg as follows

  ffmpeg -i output.dpx -pix_fmt yuv420p -c:v libx264 -crf 28 -profile:v baseline fromdpx.h264

  This also gives me a blank video.

  Could someone please point out to me what is going on here ? Why does the first method work and the second does not ?

  Thank you.

• How to plot animated time series in R ?

  28 août 2016, par pOrlando

  I am trying use the ’animation’ package in R to plot an animated time series.

  My dataset consists of a time vector and a value vector, each with 1800 rows.

  I keep getting an error message after running the loop which reads :

  Error in jpeg(gname[i]) : unable to start jpeg() device
  
  In addition: Warning messages:
  
  1: In jpeg(gname[i]) : unable to open file 'g11:30:00.jpg' for writing
  
  2: In jpeg(gname[i]) : opening device failed

  Here’s the source code

  timemax<-1800
  
  setwd("~/Documents/Animation/")
  
  graphdata<-read.csv("filling_line_data_construction_v2.csv")
  
  attach(graphdata)
  
  gname<-paste("g",time, ".jpg", sep="")
  
  for (i in 1:timemax){
  
      jpeg(gname[i])
  
      plot(time[1],value[1],type="l",ylim=c(0,35), xlim=c(0,100),
  
        ylim = c(0, 35),ylab = "", xlab="time")
  
      lines(time[1:i],value[1:i])
  
      dev.off(dev.cur())
  
  }

  The end goal is to string together these 1800 plots as a stop animation video by calling the ffmpeg shell :

  shell("C:/ffmpeg/bin/ffmpeg.exe -report -i g%d.jpg -b:v 2048k fillin_lineR.mpg",mustWork=FALSE)

  This is code that I’ve been trying to adapt from http://www.animatedgraphs.co.uk/LondonR.html#slide-30, but this example uses a .tif file instead of .jpg, and my computer gives me 1800 error messages when trying to make a video from .tif files...

  Thanks in advance !

• Grabbing a series of frames from an RTSP stream

  30 septembre 2012, par Burbas

  I'm looking for a way to continuously grab frames, as jpg, from a RTSP stream. I've stumbled upon ffmpeg but it seems that the time between starting it and grabbing the first frame is quite high. Is there any good tool in order to do this ?

  Regards