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• FFMPEG Speed drops and warnings

  31 July 2018, by leo_dragons

  I’ve been trying to stream from a BlackMagic DeckLink Mini Recorder to 4 different outputs using FFMPEG, but i get a huge delay let say more than 60 seconds of delay, it takes a long time to buffer on any player and when i check the terminal i get these warnings:

  [decklink @ 0x4655e40] Decklink input buffer overrun!

  I’ve also noticed that i have a very slow capture speed like 0.5x. Here’s the string i use, i’m currently running on CentOS 7.5:

  ffmpeg -f decklink -i "DeckLink Mini Recorder" -y -pix_fmt yuv420p -vcodec h264 -preset ultrafast -tune zerolatency -b 900k -g 48 -framerate 30 -movflags +faststart -vf scale=1280:720 -bufsize 400k -maxrate 1200k -benchmark -f flv "rtmp://10.0.0.172:1935/CAMARAS/live9" -vcodec h264 -preset ultrafast -tune zerolatency -b 700k -g 48 -framerate 30 -movflags +faststart -vf scale=854:480 -bufsize 400k -maxrate 1000k -benchmark -f flv "rtmp://10.0.0.172:1935/CAMARAS/live10" -vcodec h264 -preset ultrafast -tune zerolatency -b 400k -g 48 -framerate 30 -movflags +faststart -vf scale=854:480 -bufsize 400k -maxrate 500k -benchmark -f flv "rtmp://10.0.0.172:1935/CAMARAS/live11" -vcodec h264 -preset ultrafast -tune zerolatency -b 200k -g 48 -framerate 30 -movflags +faststart -vf scale=640:360 -bufsize 300k -maxrate 300k -benchmark -f flv "rtmp://10.0.0.172:1935/CAMARAS/live12" > /dev/null 2>&1 &

  But if i run this string alone i get decent capture speed, but i still have an awful latency 30ish seconds:

  ffmpeg -f decklink -i "DeckLink Mini Recorder" -y -pix_fmt yuv420p -vcodec h264 -preset ultrafast -tune zerolatency -b 900k -g 48 -framerate 30 -movflags +faststart -vf scale=1280:720 -bufsize 400k -maxrate 1200k -benchmark -f flv "rtmp://10.0.0.172:1935/CAMARAS/live9"

  Any help will be highly appreciated.

  Tahnk you.

• Anomalie #2380 (Nouveau): bandeau

  24 October 2011, by Alexandre C

  Un petit bug sur le bandeau de /ecrire en SPIP 3.0.0-beta [18629], pour le second niveau des raccourcis de création d’objets : Si l’on a mis dans ses préférences "Menu de navigation"=>Afficher uniquement le texte les mini-icones gauche restent, mais celles de droite disparaissent et se retrouvent (...)

• Why is there ffmpeg codec noise when encoding test tone?

  27 February 2017, by JackOfAllTrades

  I used FFmpeg to generate a test clip with color bars and a tone. I also made a special filter to dump out the raw audio data to check it. I was surprised to find that there is significant noise riding on the audio tone after it has gone through the AAC codec. Is this expected? Is there a way to prevent it?

  To make the test file I used:

  ffmpeg -f lavfi -i "smptehdbars=duration=600:size=1280x720:rate=59.94" -qscale:v 1 -pix_fmt yuv420p smpte_r59_720.mp4

  then

  ffmpeg -i smpte_r59_720.mp4 -f lavfi -i "sine=frequency=1000:sample_rate=48000:duration=600" -qscale:v 1 -vcodec copy -c:a aac -b:a 192k -shortest -map 0:0 -map 1:0 smpte_r59_720T.mp4

  and then

  ffmpeg -i smpte_r59_720T.mp4 -y -map 0 -acodec aac -vcodec libx264 -crf 23 -bsf:v h264_mp4toannexb smpte_r59_720T.ts

  (Trying to do this all in one step kept failing.)

  Other variations on this have varying degrees of noise, sometimes above nominal amplitude and sometimes below.

  After finding this problem I pulled a third party test tone .WAV file with 44.1KHz sample rate from the web and checked it. The raw file is clean, but the encoded file I made has noise.

  Noise on TS SMPTE bars

  Clean audio from MP4