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• How to change mjpeg to yuyv422 from a webcam to a v4l2loopback ?

  3 janvier 2020, par Dev Null

  Backstory : One livestreaming site I use isn’t smart enough to detect the capabilities of my webcam (Logitech Brio, 4k), and instead just uses the default frames per second settings, which is 5fps.

  (full solution walk-through in the answer)

  The best solution I could think of (besides changing livestream providers) was to create a loopback virtual webcam using v4l2loopback that I could force to have the exact settings I wanted to use on that livestream site.

  For the brio, the higher frame rates come with mjpeg, not the default yuyv.

  Problem 1 :

  I could easily read mjpeg, but unfortunately kept banging my head against the wall because v4l2loopback evidently only wanted yuyv.

  I tried things like :

  ffmpeg -f v4l2              \
  
         -input_format mjpeg  \
  
         -framerate 30        \
  
         -video_size 1280x720 \
  
         -i /dev/video0       \
  
         -vcodec copy         \
  
         -f v4l2 /dev/video6

  and

  ffmpeg -f v4l2              \
  
         -input_format mjpeg  \
  
         -framerate 30        \
  
         -video_size 1280x720 \
  
         -i /dev/video0       \
  
         -vcodec yuyv422      \ # this line changed (even tried "copy")
  
         -f v4l2 /dev/video6

  But they wouldn’t work. I got errors like :

  Unknown V4L2 pixel format equivalent for yuvj422p

  and

  ...deprecated pixel format used, make sure you did set range correctly...

  ...V4L2 output device supports only a single raw video stream...

  Eventually I got this to work :

  ffmpeg -f v4l2              \
  
         -input_format mjpeg  \
  
         -framerate 30        \
  
         -video_size 1280x720 \
  
         -i /dev/video0       \
  
         -pix_fmt yuyv422     \ # The winning entry
  
         -f v4l2 /dev/video6

  Problem 2

  The next problem was getting chrome to see the virtual webcam. It worked correctly with guvcview, and on firefox I could use webcam testing sites and it would pick the virtual camera up without a problem.

  Turns out google, in it’s overly-protective nature (while it’s siphoning off all our data, btw), doesn’t want to use webcams that can be read and written to.

  So when starting v4l2loopback you have to tell it to announce that it’s "read only" to consumers like chrome.

  Here’s the exact modprobe I use that works :

  sudo modprobe v4l2loopback devices=1 exclusive_caps=1

• avfilter/graphparser : allow specifying filter@id as filter instance

  17 mai 2017, par Muhammad Faiz

  avfilter/graphparser : allow specifying filter@id as filter instance
  See http://lists.ffmpeg.org/pipermail/ffmpeg-user/2017-April/035975.html
  
  Parsed_filter_X could remain and user can override it with custom one.
  Example :
  
  ffplay -f lavfi "nullsrc=s=640x360,
  
  sendcmd='1 drawtext@top reinit text=Hello ; 2 drawtext@bottom reinit text=World',
  
  drawtext@top=x=16:y=16:fontsize=20:fontcolor=Red:text='',
  
  drawtext@bottom=x=16:y=340:fontsize=16:fontcolor=Blue:text=''"
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Muhammad Faiz <mfcc64@gmail.com>
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/graphparser.c

• Rails 5 - Concurrent large Video uploads and FFMPEG encoding in the background is making the server very slow

  8 septembre 2022, par Milind

  I have a working Rails 5 apps using Reactjs for frontend and React dropzone uploader to upload video files using carrierwave.

  



  So far, what is working great is listed below -

  



  

  1. User can upload videos and videos are encoded based on the selection made by user - HLS or MPEG-DASH for online streaming.

  


  2. Once the video is uploaded on the server, it starts streaming it by :-


     

     • FIRST,copying video on /tmp folder.

     


     • Running a bash script that uses ffmpeg to transcode uploaded video using predefined commands to produce new fragments of videos inside /tmp folder.

     


     • Once the background job is done, all the videos are uploaded on AWS S3, which is how the default carrierwave works

     


  


  3. So, when multiple videos are uploaded, they are all copied in /tmp folder and then transcoded and eventually uploaded to S3.

  


  



  My questions, where i am looking some help are listed below -

  



  1- The above process is good for small videos, BUT what if there are many concurrent users uploading 2GB of videos ? I know this will kill my server as my /tmp folder will keep on increasing and consume all the memory, making it to die hard.How can I allow concurrent videos to upload videos without effecting my server's memory consumption ?

  



  2- Is there a way where I can directly upload the videos on AWS-S3 first, and then use one more proxy server/child application to encode videos from S3, download it to the child server, convert it and again upload it to the destination ? but this is almost the same but doing it on cloud, where memory consumption can be on-demand but will be not cost-effective.

  



  3- Is there some easy and cost-effective way by which I can upload large videos, transcode them and upload it to AWS S3, without effecting my server memory. Am i missing some technical architecture here.

  



  4- How Youtube/Netflix works, I know they do the same thing in a smart way but can someone help me to improve this ?

  



  Thanks in advance.