Recherche avancée

Sur d’autres sites (16033)

• how to create a small m3u8 clip from another m3u8 clip using node

  12 janvier 2021, par Alan

  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:13
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:12.960000,
https://d3s84sk2607r1u.cloudfront.net/video_866552260.ts
#EXTINF:8.760000,
https://d3s84sk2607r1u.cloudfront.net/video_866552261.ts
#EXTINF:10.520000,
https://d3s84sk2607r1u.cloudfront.net/video_866552262.ts
#EXTINF:9.800000,
https://d3s84sk2607r1u.cloudfront.net/video_866552263.ts
#EXTINF:10.000000,
https://d3s84sk2607r1u.cloudfront.net/video_866552264.ts
#EXTINF:10.240000,
https://d3s84sk2607r1u.cloudfront.net/video_866552265.ts
#EXT-X-ENDLIST



  


  So here it is an m3u8 file. I am trying to cut it and create a new clip let's say 15 seconds with the first two ts files and remove the others. This new clip will be in m3u8 format and will look like

  


  


  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:13
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:12.960000,
https://d3s84sk2607r1u.cloudfront.net/video_866552260.ts
#EXTINF:2.040000,
https://d3s84sk2607r1u.cloudfront.net/video_866552261.ts
#EXT-X-ENDLIST



  


  I am using node js and FFmpeg. So is there a way to create a small clip which will be a m3u8 file, from this m3u8 file. I am trying to create a script that will execute. So if it's not node js then any other like java or python will be helpful for me

  


  


  I am trying to create a script.js that will run on my command like

  


  node script.js start_time end_time ./path/file.m3u8

  


  


  that will generate a new m3u8 file

  


• slicing and seeking extremeley small sections of video in ffmpeg

  20 février 2021, par Zarc Rowden

  I am writing a program that maps midi data to timestamps in a video. The end result is a kind of automatic generation of audio visuals for beat making or techno heads. The program takes in midi, slices a video into chunks based on the midi events and mappings and finally joins the slices into a video with 1:1 timing of monophonic midi notes to sections of a video.

  


  When it is successful, the result is very cool and watching the video jump around and lock in to midi notes is very interesting

  


  However, I am affraid that the ffmpeg commands I use are not giving exact results.

  


  The code I feed to ffmpeg looks like this

  


  EVENTS : left is midinote number, right is time from start of recording in which note occurs.

  


    [{"note"=>"start", "timestamp"=>0.0},
   {"note"=>48, "timestamp"=>0.5700000037904829},
   {"note"=>51, "timestamp"=>383.7100000018836},
   {"note"=>45, "timestamp"=>884.3500000002678},
   {"note"=>48, "timestamp"=>999.0449999968405},
   {"note"=>51, "timestamp"=>1383.544999996957},
   {"note"=>45, "timestamp"=>1884.2599999989034},
   {"note"=>48, "timestamp"=>1998.890000002575},
   {"note"=>51, "timestamp"=>2383.4199999982957},
   {"note"=>45, "timestamp"=>2884.1000000029453},
   {"note"=>48, "timestamp"=>2998.7200000032317},
   {"note"=>51, "timestamp"=>3383.2800000018324},
   {"note"=>45, "timestamp"=>3883.894999999029},
   {"note"=>48, "timestamp"=>3998.6250000001746},
   {"note"=>51, "timestamp"=>4384.550000002491},
   {"note"=>45, "timestamp"=>4883.780000003753},
   {"note"=>48, "timestamp"=>4998.404999998456},
   {"note"=>51, "timestamp"=>5384.39500000095},
   {"note"=>45, "timestamp"=>5883.565000003728},
   {"note"=>48, "timestamp"=>5998.464999996941},
   {"note"=>51, "timestamp"=>6384.254999997211},
   {"note"=>45, "timestamp"=>6883.4550000028685},
   {"note"=>48, "timestamp"=>6998.585000001185},
   {"note"=>51, "timestamp"=>7384.055000002263},
   {"note"=>45, "timestamp"=>7883.249999998952},],


  


  MAPPINGS : left side is midi note, right is timestamp in seconds

  


  {
 48=>234.3489,
 45=>124.334489,
 51=>2789.34,
}


  


  That Events are a sequential array of midi notes and time taken from recordings or standard midi file. The number is in milliseconds but I convert for ffmpeg before feeding the arguments.

  


  The mappings are just in seconds and tell the program what to show when certain midi notes are encountered as we loop through the events and begin slicing the video.

  


  The command I send to ffmpeg is constructed like this :

  


  "ffmpeg -an -y -ss #{begin_at} -i #{project_tempfile_url} -t #{slice_duration} -c:v libx264 #{temp_url}"


  


  When I concatenate these slices, they only look exact when my notes are very consistent like a kickdrum doing 4/4 rythms. Anything too fast or varied creates unpleasant results.

  


  Is there a specific set of commands that will tell ffmpeg to cut down to the frame ? I think keyframe are not an ideal answer but not sure. I also think I can adjust by making sure that I only ever map the notes to keyframes, I can settle for it but it would be great if I could just cut almost anywhere between start and end like ANYWHERE like

  


    rand(0...video.length)
  # and then have
  332.3253613134


  


  But I may just be dreaming :P

  


  Do you think that I would be better off writing a custom c program to cut frames like this ? I understand that frame rates could be an issue and that there may actually not be any data at 7.34667898999 seconds and that it might be here instead : 7.356788722342 and that ffmpeg probably searches for the nearest frame from whatever timestamp you input, but I feel like there must be a way to get good results still despite these limitations.

  


  Thank you so much in advance for those who take the time to read this and understand this issue.

  


• How to insert lots of small looped videos or GIFs in HTML (thousand or more), but keep decent quality and page size ?

  10 novembre 2020, par Armen Avakian

  I need to place a thousand of small GIFs (20x20 pixels or slightly bigger) in the HTML. Almost all of them are visible at once, when page is loaded. There are several ways I tried, but each one has a problem.

  


  Way 1. Placing GIF images. GIFs are inefficient and heavy, so a lot of traffic will be needed to load the page. WEBP is better, but it is not supported fully in recent versions of Safari. So I made GIFs smaller, with low quality. In Safari I am loading this low quality GIFs, in other browsers I load WEBP. And it works nice, but the problem is that with a thousand of small GIFs, a user will need to load more than 600 MB for this page... So this way is... not as good. I can make them even lower in quality, but I don't want to make experience worse. Even now the quality is average.

  


  Way 2. Making MP4 and embedding them into looped video tags with autostart, so they look like a GIF. This way would be AWESOME, because MP4 is much smaller in size, but it keeps good quality. The problem here is when I add even 10-15 small videos in tags, the browser can't manage with it and starts working veeeery slowly. Each video is becoming very slow. So the experience is even worse than with low quality GIFs.

  


  My question is – how to achieve best way in this case, keeping decent quality and low sizes for each video ? Maybe I can use somehow MP4 videos in another way ? Does anyone know how to solve this issue ?

  


  For scaling videos and converting to GIF/WEBP I use ffmpeg.