Sur d’autres sites (7770)

• Extracting media duration in R

  27 septembre 2015, par Jason French

  I’m investigating the fastest way to extract film duration in R using ffprobe and the data.table package.

  Setup Example Source Media

  wget https://ia801403.us.archive.org/13/items/AboutBan1935/AboutBan1935_512kb.mp4
  
  mv AboutBan1935_512kb.mp4 one.mp4
  
  for file in two.mp4 three.mp4 four.mp4 five.mp4 ; do cp one.mp4 "$file" ; done

  Various Approaches

  library(data.table)
  
  library(parallel)
  
  
  
  # Get locations
  
  executables <- Sys.which(c('ffprobe', 'ffmpeg'))
  
  
  
  # Duration Function
  
  get_duration_parallel <- function(files){
  
    mclapply(X = files, FUN = function(file){
  
      ffprobe_duration <- paste(executables['ffprobe'],
  
                                " -v quiet -print_format compact=print_section=0:nokey=1:escape=csv -show_entries format=duration ",
  
                                '"', file, '"', sep = "")
  
  
  
      file_duration <- as.numeric(system(command = ffprobe_duration, intern = TRUE))
  
      return(file_duration)
  
    }, mc.cores = detectCores())
  
  }
  
  
  
  get_duration <- function(files){
  
    sapply(X = files, FUN = function(file){
  
      ffprobe_duration <- paste(executables['ffprobe'],
  
                                " -v quiet -print_format compact=print_section=0:nokey=1:escape=csv -show_entries format=duration ",
  
                                '"', file, '"', sep = "")
  
  
  
      file_duration <- as.numeric(system(command = ffprobe_duration, intern = TRUE))
  
      return(file_duration)
  
    })
  
  }
  
  
  
  # Example table
  
  dt <- data.table(Path = list.files(path = ".", pattern = "*.mp4$"))
  
  
  
  
  
  system.time(
  
    dt[, Seconds := get_duration_parallel(Path)]
  
  )
  
  # 9.667 seconds    
  
  
  
  system.time(
  
    dt[, Seconds := get_duration(Path)]
  
  )
  
  # 0.078 seconds

  Am I missing any obvious speed-ups ? Scanning a 500-file archive for ffprobe stats takes 5 minutes in testing.

• Introducing media accessibility into HTML5

  11 avril 2010, par silvia

  In recent months, people in the W3C HTML5 Accessibility Task Force developed two proposals for introducing caption, subtitle, and more generally time-aligned text support into HTML5 audio and video. These time-aligned text files can either come as external files that are associated with the (...)

• Using ffmpeg with Flash Media Server and HDS

  20 avril 2012, par Jonathan

  I want to use ffmpeg to encode and publish a live stream to Flash Media Server. In order to support iOS devices, I need to implement HTTP Live Streaming as well. The video needs to be in H.264 format and the audio should be AAC. I don't have much experience working with ffmpeg, and I'm having a hard time getting this to work. This is the command that I've tried (and some variations as well) :

  ffmpeg.exe -threads 15 -f dshow -i video="USB2.0 UVC WebCam":audio="Microphone (Realtek High Defini" \
  
        -map_channel 0.1.1 -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 \
  
        -s vga -vb 100k -f flv "rtmp:///livepkgr/livestream1?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s qvga -vb 200k \
  
        -f flv "rtmp:///livepkgr/livestream2?adbe-live-event=liveevent" \
  
        -r 24 -acodec libvo_aacenc -ar 22050 -ab 128k -vcodec libx264 -s vga -vb 350k 
  
        -f flv "rtmp:///livepkgr/livestream3?adbe-live-event=liveevent"

  When I run this, it appears to connect to FMS, but then I get a lot of error messages about dropped frames - I'm not sure if ANY frames get encoded successfully. My CPU usage is very high as well. I get a 404 error from FMS when I enter the URL of the *.m3u8 file for one of the individual streams (the main livestream.m3u8 file is accessible though). I have also tried outputting to a file instead of FMS, with no success. All I get is some very garbled sound and no video.

  Any suggestions for what options/commands I should use to get this working ? Is anyone using ffmpeg with FMS to do HTTP Dynamic Streaming / HLS with MP4 video ? I've been struggling to get HDS/HLS working for some time now, and any help would be much appreciated ! It shouldn't make a difference, but I'm using FMS on Amazon EC2 with their AMI image.

  Thanks !