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• SRT protocol not found - Raspbery Pi 4 via ffmpeg

  12 août 2021, par Tim Martin

  We tried to stream from a rasp Pi 4 via SRT, but we got a error : "protocol not found". Our command line is :

  


  ffplay srt://127.0.0.1:9500?mode=listener&latency=20000


  


  We tried the following guides :
https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu
how to compile ffmpeg with enabling libsrt
https://www.undergroundnews.dk/index.php/item/107-rtmp-eller-srt-streaming

  


  Those guides worked so far and compiled but we still got the error message.

  


  Do you have any ideas how to get the srt protocol working on a pi via ffmpeg ?

  


• Find out what device to use for capturing with ffmpeg ?

  14 septembre 2013, par wvxvw

  I'm trying to broadcast my screen and I cannot capture audio. There's one complication however. I don't have pulseaudio, and it simply doesn't work on my system, so installing it is out of question. Below is the command I'm trying :

  ffmpeg -f alsa -i ??? -f x11grab -s 1920x1200 -r 15 -i :0.0 \
  
      -acodec pcm_s16le -vcodec libx264 \
  
      -preset fast -pix_fmt yuv420p -s 1280x800 -threads 0 -f flv "$URL"

  Here's the list of my audio devices :

  $ aplay -L
  
  null
  
      Discard all samples (playback) or generate zero samples (capture)
  
  default:CARD=PCH
  
      HDA Intel PCH, ALC269VB Analog
  
      Default Audio Device
  
  sysdefault:CARD=PCH
  
      HDA Intel PCH, ALC269VB Analog
  
      Default Audio Device
  
  front:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      Front speakers
  
  surround40:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      4.0 Surround output to Front and Rear speakers
  
  surround41:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      4.1 Surround output to Front, Rear and Subwoofer speakers
  
  surround50:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      5.0 Surround output to Front, Center and Rear speakers
  
  surround51:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      5.1 Surround output to Front, Center, Rear and Subwoofer speakers
  
  surround71:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Analog
  
      7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
  
  iec958:CARD=PCH,DEV=0
  
      HDA Intel PCH, ALC269VB Digital
  
      IEC958 (S/PDIF) Digital Audio Output
  
  hdmi:CARD=NVidia,DEV=0
  
      HDA NVidia, HDMI 0
  
      HDMI Audio Output
  
  hdmi:CARD=NVidia,DEV=1
  
      HDA NVidia, HDMI 0
  
      HDMI Audio Output
  
  hdmi:CARD=NVidia,DEV=2
  
      HDA NVidia, HDMI 0
  
      HDMI Audio Output
  
  hdmi:CARD=NVidia,DEV=3
  
      HDA NVidia, HDMI 0
  
      HDMI Audio Output

  I know that ??? should be something like hw:X,Y, but maybe it can be something else. I can't find the corresponding entry in the man page.

  As an aside, it would be great if you can suggest another audio codec. I can't find what are the options, and this particular one isn't compatible with FLV because of too high bitrate.

  PS. This is the error I'm getting :

  Could not write header for output file #0 (incorrect codec parameters ?): Invalid data found when processing input

• Set the time according to the image height

  5 août 2019, par Võ Nhân

  I am creating video from the image using ffmpeg, I have some problems with image height and video length, I want to set the time automatically according to the image length.Is it possible to set the time -t to the automatic value ?

  ffmpeg -y -loop 1 -i "{output}_cut1.jpg" -ss 0 -t 25 -r 1 -loop 1 -i 01.png -ss 0 -t 25 -filter_complex " [1:v] scale=w=1:h=1[fg]; [0:v] scale=w=-2:h=3*ih, crop=w=3*1988:h=3*1600/1.2:y=t*(in_h-out_h)/25 , scale=w=1920:h=1080,  setsar=1 [bg] ; [bg][fg]overlay=shortest=1[v] " -map "[v]" -c:v h264 -crf 18 -preset ultrafast "{output}_cut1.mp4"