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• Start rtl_fm and ffmpeg when connecting to a controller and return the stream

  14 février 2017, par yglodt

  I would like to run rtl_fm and ffmpeg on demand from within a Spring Controller, with parameters from the calling url, and return the stream to the caller.

  The command-line to run would more or less be :

  rtl_fm -f 105000K -M fm -s 170k -A std -l 0 -E deemp -r 44.1k | \
  
  ffmpeg -f s16le -ac 1 -i pipe:0 -acodec libmp3lame -ab 128k -f mpeg -

  105000 is the frequency in kHz and should be taken from a request parameter or path variable.

  The url (Controller) should return the stream so that it can be played in a remote vlc.

  When disconnecting from the url (stopping vlc playback), the rtl_fm and ffmpeg processes should be ended immediately.

  Is that feasible ?

• 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 ?