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• Concatenation and Transcoding of MPEG-TS files FFMPEG

  20 décembre 2020, par SquawkBirdies

  I have a DVR which records over-the-air TV and saves the recordings in the MPEG-TS format, splitting each episode across multiple files, each 500 MB in size.

  



  To simplify archiving, I have been trying to write a shell script to automate the process of concatenating the files together and transcoding them into a more common video format, like h.264.

  



  Here are the steps I have performed so far :

  



  

  • I wanted to make sure that the files I was getting were valid in the first place. To test this, each section was transcoded in Handbrake before being merged using ffmpeg's concat command. This worked, but was manual and added an annoying black frame between each section.

  


  • I wrote a shell script to find all the sections of an episode in a folder and put the file names into a text file that the concat demuxer could parse.

  


  • Tested this command :

  


  



  


  


  ffmpeg -hide_banner -f concat -i video_files_tmp.txt -c:v libx264 -pix_fmt yuv420p -c:a aac $2$OUTPUT_FILE_NAME

  


  


  




  During the transcode, this would throw many warnings and errors, such as "PES packet size mismatch". At some point, it would warn that more than 1,000 frame were skipped. When the output was played, it would skip frames and result in a file where the video froze partway through but the audio continued playing. I tried adding -vsync 0 to the output as well.

  



  

  • Then, tried splitting the concatenation and transcode into two steps :

  


  



  


  


  ffmpeg -hide_banner -f concat -i video_files_tmp.txt -c copy output_tmp.ts
ffmpeg -hide_banner -i output_tmp.ts -c:v libx265 -pix_fmt yuv420p -c:a aac $2$OUTPUT_FILE_NAME

  


  


  




  This did basically the same thing as before.

  



  

  • Tried using the libx265 encoder instead. Same result.

  


  • Then, I tried just playing the concatenated MPEG-TS file directly, which also would freeze at some point during the playback.

  


  



  I was wondering about what ffmpeg flags or options to set to get this working, or other options I could try ? Thanks !

  


• FFMPEG UDP MPEG2TS to Cable TV Channel - Video & Audio Problems

  30 janvier 2019, par user2884023

  Channel Feed Distored Picture

  $ ffmpeg
  
  -re
  
  -i playlist1.txt
  
  -b:v 15000k 
  
  -bufsize 15000k
  
  -maxrate 16000k
  
  -f mpegts "udp://XXX.XXX.X.XXX:XXXX"

  I have mpeg2.ts files encoded to CBR15mbs.
  The files are set to different frame rates. Although initial testing was just playing 1 file.
  They are currently 1080p I think without declaring the frame rate, they are defaulting to 30fps.
  From the server locally via Port2 (that we are using to send our feed), everything plays fine via FFPLAY.
  The final out put local CATV is pixelated and distorted, the video is missing data playing slowly and the audio is choppy / distorted.
  I even tried just a 192kps .mp2 and it played distorted on the CATV channel.
  They set me up with a cable modem. 2 ports, 1 WAN, 1 a dedicated port to feed their head end and I have a fiber synchronous 20/20 connection.

  I am guessing its a packet issue, perhaps on our end with our FFMPEG setup ? And maybe FFPLAY isn’t as sensitive to the actual distro process.

  Perhaps the secret lies here, but there isn’t much info about them, even scouring the net.

  ?pkt_size=188&buffer_size=65535

  For example what is this one :

  broadcast=1|0

  Explicitly allow or disallow UDP broadcasting.

  I apologize if data is missing, please ask questions. I didn’t want to write a novel.

  I am hoping some can provide the correct code so my signal is corrected. I assume the problem is on our end, and not the CATV end. At least I can try some solutions on our end first. I can make real-time FFMPEG changes to the server, and see the channel results instantly so that helps.

  Finally, the fact it wouldn’t even play a .mp2 audio file cleanly on the channel, does make me wonder, is there a problem on their end, or is it a config on our end, and we just need the correct answer ?

• HEVC File bigger after converting from h264

  26 janvier 2019, par Aaroknight

  I’m currently working an an automated Python script for indexing and converting all my movies and episodes with ffmpeg. I use subprocess.call() for running the ffmpeg command and tested this command with some movies. As expected the big h264 files were converted to merely one third of what they used to have.

  But now that I was testing the method I found that a converted episode (about 400MB in h264) had over 1,6GB in hevc. I have absolutely no idea why the new file would be that much bigger in hevc.
  This is my code :

  def convert(path):
  
      outvid = path.strip(".mkv") + "h265.mkv"
  
  
  
      cmd = ["ffmpeg", "-i", path, "-map", "0", "-map_metadata", "0", "-map_chapters", "0", "-c:v", "libx265",
  
             "-c:a", "copy", "-c:s", "copy", "-preset", "ultrafast", "-x265-params", "lossless=1", outvid]
  
      subprocess.call(cmd)
  
  
  
  convert("/Volumes/2TB/Black Butler/Season 1/Black Butler S01E01.mkv")

  I don’t have that much experience with ffmpeg, nor with subprocess. This is one of my first bigger projects. I hope someone can tell me what the problem might be.

  UPDATE
  Problem applies only for small video files. I now just check for the file size and skip the small files. Wouldn’t have made much of a difference anyway.