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• Electron ffmpeg integration

  27 avril 2017, par Raider Dave

  I am in way over my head here. I am normally a coldfusion/javascript/jquery developer but now have taken on a task that assumes I know more than I do.

  I am trying to write an application in electron that will allow me to select a group of video files and convert them to mp4 files while also compressing them. The files are football plays and a normal game consists of about 160 plays and 18gb. We need to compress these down to about 4gb. I have used programs like Prism to do this, but the intended users are not technically savvy nor do they all have windows - some have Macs.

  I have an electron project that I have started and got the first part to work. I can start the app and select the input files. But I have tried all kinds of different solutions found online to call ffmpeg and pass it the parms to convert a file. Is there an easy way to call ffmpeg with parms and then wait for it to finish before continuing ?

  I am on Windows 10 but will also need to run on Apple OS. Please, if you have a simple example of how to do this, I would appreciate it.

  Thanks !
  Dave

• Why is FFMpeg outputting wrong NAL unit types ? (javascript h264 livestream)

  17 juillet 2018, par Yeti

  I am trying to set up a livestream in the browser using h264 encoding, in which javascript decodes the h264 frames and paints it on a Canvas-element (or using WebGL).

  Both Broadway and Prism implement decoding NAL units of type 1, 5, 7, and 8.

  My current setup is as follows :

  • FFMpeg outputs an MPEG-TS stream with h264 data
  • The stream is piped to netcat which listens on port 8084
  • A websocket server in NodeJS pipes data from port 8084 to clients on 8085
  • The jsmpeg library decodes MPEG-TS into separate NAL units
  • The separate NAL units are decoded by Broadway or Prism which outputs to a canvas

  I am using this FFMpeg command :

  ffmpeg -f v4l2 -i /dev/video0 -r 15 -c:v h264_nvenc -pix_fmt yuv420p -b:v 500k -profile:v baseline -tune zerolatency -f mpegts - | nc -l -p 8084 127.0.0.1

  The problem is that the NAL units I’m getting are of type 9 (or maybe 6 ?), here is the header of one of the NAL units that javascript is receiving, in Base64 and binary formatting :

  echo "AAAAAQnwAAAAAQYBBAAECBCAAAAAAWHg" | base64 -d | xxd -b
  
  00000000: 00000000 00000000 00000000 00000001 00001001 11110000  ......
  
  00000006: 00000000 00000000 00000000 00000001 00000110 00000001  ......
  
  0000000c: 00000100 00000000 00000100 00001000 00010000 10000000  ......
  
  00000012: 00000000 00000000 00000000 00000001 01100001 11100000  ....a.

  Neither Broadway nor Prism supports these NAL unit types. How can I configure FFMpeg to only output NAL units of type 1, 5, 7, and 8 ?

  ---

  EDIT : I have also tried the following command :

  ffmpeg -f v4l2 -i /dev/video0 -r 15 -c:v h264_nvenc -pix_fmt yuv420p \
  
      -b:v 500k -profile:v baseline -tune zerolatency \
  
      -movflags frag_keyframe+empty_moov -g 52 -f mp4 - \
  
      | nc -l -p 8084 127.0.0.1

  Which encodes to mp4, and from there I try to parse NAL units starting with three zero bytes. The lines look all similar to the following :

  echo "AAAACAYBBABOCBCAAAARemHk4f8df1Su" | base64 -d | xxd -b
  
  00000000: 00000000 00000000 00000000 00001000 00000110 00000001  ......
  
  00000006: 00000100 00000000 01001110 00001000 00010000 10000000  ..N...
  
  0000000c: 00000000 00000000 00010001 01111010 01100001 11100100  ...za.
  
  00000012: 11100001 11111111 00011101 01111111 01010100 10101110  ....T.

  That is type 6 (00110 in the 5th byte), still not the desired NAL unit type.

  ---

  UPDATE : The reason it didn’t work for me was a matter of an encoding/decoding issue between chars and bytes in Javascript. I have put the working code on github for others who may want to do a similar thing.

  Concerning the NAL units, it turns out the raw video of FFMpeg output contained type 6 of only a few bytes, followed by type 1 that has the frame data. The type 6 can be discarded. Thanks to the comments and accepted answer for the insight into this.

• Edit ffmpeg arguments while playing

  12 mars 2019, par C0d0r

  I am building a client (discord.js) that plays music from youtube. Before the client starts playing the ffmpeg-arguments (filters etc.) can be edited and piped into the stream. I use prism-media (npm) to define the args.

  My Question : How is it possible to edit these arguments while the client is playing ? f.ex. disable in the middle of a song etc...

  The code basically looks like in the Readme example on github : https://github.com/amishshah/prism-media/tree/dev