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• lavc/flacdsp : optimise RVV vector type for lpc16

  14 mai 2024, par Rémi Denis-Courmont

  lavc/flacdsp : optimise RVV vector type for lpc16
  This calculates the optimal vector type value at run-time based on the
  
  hardware vector length and the FLAC LPC prediction order. In this
  
  particular case, the additional computation is easily amortised over
  
  the loop iterations :
  T-Head C908 :
  
      C     V before  V after
  
   1   48.0    214.7     95.2
  
   2   64.7    214.2     94.7
  
   3   79.7    213.5     94.5
  
   4   96.2    196.5     94.2 #
  
   5  111.0    195.7    118.5
  
   6  127.0    211.2    102.0
  
   7  143.7    194.2    101.5
  
   8  175.7    193.2    101.2 #
  
   9  176.2    224.2    126.0
  
  10  191.5    192.0    125.5
  
  11  224.5    191.2    124.7
  
  12  223.0    190.2    124.2
  
  13  239.2    189.5    123.7
  
  14  253.7    188.7    139.5
  
  15  286.2    188.0    122.7
  
  16  284.0    187.0    122.5 #
  
  17  300.2    186.5    186.5
  
  18  314.0    185.5    185.7
  
  19  329.7    184.7    185.0
  
  20  343.0    184.2    184.2
  
  21  358.7    199.2    183.7
  
  22  371.7    182.7    182.7
  
  23  387.5    181.7    182.0
  
  24  400.7    181.0    181.2
  
  25  431.5    180.2    196.5
  
  26  443.7    195.5    196.0
  
  27  459.0    178.7    196.2
  
  28  470.7    177.7    194.2
  
  29  470.0    177.0    193.5
  
  30  481.2    176.2    176.5
  
  31  496.2    175.5    175.7
  
  32  507.2    174.7    191.0 #
   # Power of two boundary.
  With 128-bit vectors, improvements are expected for the first two
  
  test cases only. For the other two, there is overhead but below noise.
  
  Improvements should be better observable with prediction order of 8
  
  and less, or on hardware with larger vector sizes.
  

  • [DH] libavcodec/riscv/flacdsp_init.c
  • [DH] libavcodec/riscv/flacdsp_rvv.S

• ffmpeg encoder streaming issues

  8 août 2017, par bobsingh1

  I am trying to build ffmpeg encoder on linux. I started with a custom built server Dual 1366 2.6 Ghz Xeon CPUs (6 cores) with 16 GB RAM with Ubuntu 16.04 minimal install. Built ffmpeg with h264 and aac. I am taking live source OTA channels and encoding/streaming them with following parameters

  -vcodec libx264 -preset superfast -crf 25 -x264opts keyint=60:min-keyint=60:scenecut=-1 -bufsize 7000k -b:v 6000k -maxrate 6300k -muxrate 6000k -s 1920x1080 -format yuv420p -g 60 -sn -c:a aac -b:a 384k -ar 44100

  And I am able to successfully udp out using mpegts. My problem starts with 5th stream. The server can handle four streams and as soon as I introduce 5th stream I start seeing hiccups in output. Looking at my cpu usage using top I still see only 65% to 75% usage with occasional 80% hit. Memory usage is well within acceptable parameters. So I am wondering either top is not giving me accurate cpu usage or something is not right with ffmpeg. The server is isolated for udp in/out on a 1 Gbps network.

  I decided to up the cpu power and installed two 3.5 Ghz CPUs (6 cores) thinking it was perhaps the cpu clock. To my surprise the results were no different. So now I am wondering is there some built in limit I am hitting when I process at 1080p. If I change the resolution to 720p it is able to process 8 streams but 720 is not acceptable.
  My target is 10 1080p streams per server.
  So my questions are
  1. If I use a quad motherboard and up the cpu count to 4 (6 or 8 cores) will I get 10 1080p streams ? Is there any theoretical max I can go with ffmpeg per machine ?
  2. Do cores matter more or does clock matter more ?
  3. Any suggestions in improvement with my options. I have tried ultrafast preset but the output quality is unacceptable.

  Thanks in advance

• Plex DVR File Rename on FFMPEG Encoding

  11 juillet 2021, par Brent Johnson

  I'm currently using a bash shell script to encode all of my Plex DVR recordings to H.264 using FFMPEG. I'm using this little for loop I found online to encode all of the files in a single directory :

  


  for i in *.ts;
    do echo "$i" && ffmpeg -i "$i" -vf yadif -c:v libx264 -preset veryslow -crf 22 -y "/mnt/d/Video/DVR Stash/Seinfeld/${i%.*}.mp4";
done


  


  This has served its purposes well but in the process I would like to rename the file to my preferred naming convention so that the original filename Seinfeld (1989) - S01E01 - Pilot.ts is renamed to Seinfeld S01 E01 Pilot.mp4 in the encoded file. While I am already using a regular expression to change the .ts extension to .mp4, but I'm no expert with regex, especially in the bash shell so any help would be appreciated.

  


  For anyone that's interested in my Plex setup, I'm using an old machine running Linux Mint as my dedicated DVR and actually accessing it over the network with my daily driver which is a gaming machine, so more processing power for video encodes. While that one is a Windows machine, I'm using the Ubuntu bash under WSL2 to run my script, as I prefer it over the Windows command prompt or Powershell (my day job is a web developer on a company issued Mac). So here's a sample of my code for anyone that might consider doing something similar.

  


  if [[ -d "/mnt/sambashare/Seinfeld (1989)" ]]
then
    cd "/mnt/sambashare/Seinfeld (1989)"
    echo "Seinfeld"
    for dir in */; do
        echo "$dir/"
        cd "$dir"
        for i in *.ts;
            do echo "$i" && ffmpeg -i "$i" -vf yadif -c:v libx264 -preset veryslow -crf 22 -y "/mnt/d/Video/DVR Stash/Seinfeld/${i%.*}.mp4";
        done
        cd ..
    done
fi


  


  While I've considered doing a for loop for all shows, for now I am doing each show like this individually as there are a few shows I have custom encoding settings for