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• How to use ffmpeg to transcode many live streamed videos ? [closed]

  21 septembre 2020, par user14258924

  PREMISE

  


  As a pet project, I am writing a live video streaming service, in Go, that can consume video streams from OBS via SRT(TS -> h264/aac) and RTMP(FLV -> h264/aac) protocols and am planning to support streaming video from web browser as well, captured from a web camera via JS. This ingress server will receive many video streams in various containers and codecs and I need to normalize them into single container and codec and then create multiple versions for various bitrates(ie. 240p, 360p, 480p, 720p, 1080p...) to pass along where needed in the application. Each stream is split into 2 second GOP segments, separate for audio and video track, that will produce fragmented MP4 as the end result - which can be consumed by web browser.

  


  The issue is that I am using Go which has no libraries for transcoding video so I need to use either ffmpeg or vlc, which is a C code. I have decided to avoid the CGo route and use ffmpeg/vlc as standalone binaries.

  


  QUESTION

  


  My question is how to use either of these project in the most efficient way - avoiding the use of files in favour of unix sockets/streams and also the performance aspect - handling hundreds of video segments in any one time and in sufficient time to avoid creating too much of a lag beteen producer and consumer.

  


  So let's say I will pick the most used one - ffmpeg, how should I actually use it to achieve what I have described ? How would you set it up and which flags/config to use with it ?

  


  Can the performance be even achieved or is it just too much and I will need some sort of ffmpeg cluser to even come close to some useful performance/low delay ?

  


• Concatenate mkv files keeping original timestmap with gaps

  13 août 2020, par Filip

  16 days ago I had this problem : Concatenating mka files but keeping timestamp which I fixed by using amix, a delay by using start_pts from ffprobe.

  


  Today I have a new challenge like this, but with video.

  


  So I have a bunch of mkv videos. Each time a person joins a chat, a mkv is recorded, but if the person refreshes the page a new mkv is created with start_pts and start_time to what it actually is. Also if the meeting started and a person joins after a minute, the start_time is set to 1 minute. I need to merge all those mkv and pad them with blank screen when there is no feed.

  


  Like in the above example, if a person joins after a minute, the first minute is a blank screen. Also if the participant leaves and re-joins after 10 seconds, those 10 seconds are blank again.

  


  Any ideas on how to do that with ffmpeg ?

  


  Concrete example of files :

  


  0PA84c5c3f412769b311d44b159941b2d22.mkv - start_pts: 742 start_time: 0.742000
2PA73d94e8cb0f41c3002fadd6c04b4a88f.mkv - start_pts: 30761 start_time: 30.761000
3PAcd35e470325618fa8a3fb8bb5a41403e.mkv - start_pts: 50940 start_time: 50.940000
4PAddccde7b8847ecc43d5e8643b7903dba.mkv - start_pts: 69243 start_time: 69.243000


  


  The end file would result in a file with length 69.243000, first 0.742 seconds are blank and also the gaps between should also be blank.

  


  So far i've tried :

  


  ffmpeg -i 0PA84c5c3f412769b311d44b159941b2d22.mkv -i 2PA73d94e8cb0f41c3002fadd6c04b4a88f.mkv -i 3PAcd35e470325618fa8a3fb8bb5a41403e.mkv -i 4PAddccde7b8847ecc43d5e8643b7903dba.mkv -filter_complex "[0:v] [1:v] [2:v] [3:v] concat=n=4:v=1 [v]" -map "[v]" test.mkv

  


  This works but without those gaps i mentioned.

  


• Convert a Video that it can show with preview in telegram via bot api

  7 avril 2016, par siavashg

  I Have a video and i want to send it with telegram bot api by pytelegrambotapi library so i write this code for send video by bot :

  import telebot
  
  
  
  bot = telebot.TeleBot("TOKEN")
  
  
  
  @bot.message_handler(commands=['start'])
  
  def send_welcome(message):
  
      video = open('1.mp4', 'rb')
  
      bot.send_video(message.chat.id,video, duration=)
  
  
  
  bot.polling(none_stop=True)

  but I send a video and it has been sent successfully but telegram show black screen for my video like this picture
  Telegram With Black Scrreen preview of video.
  I think this is about the encoding . I found this site for encoding and it said the videos in telegram have specific format.

  Conditions to trim a video

  • Audio codec = mp4a
  • Video codec = supported by the device
  • Any side of the video more than 640px
  • Or if a side is less than 640px but video codec is h264

  Conditions to compress a video

  • Any side of the video over 640px
  • Audio codec = mp4a
  • A video encoder different than :
  • OMX.google.h264.encoder
  • OMX.ST.VFM.H264Enc
  • OMX.Exynos.avc.enc
  • OMX.MARVELL.VIDEO.HW.CODA7542ENCODER
  • OMX.MARVELL.VIDEO.H264ENCODER

  How can I send Video with blur image preview of that in telegram with telegram bot api ?