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• How do I encode a video stream to multiple output formats in parallel with ffmpeg ?

  21 juillet 2022, par rgov

  I would like to use one FFmpeg process to receive video input and then pass that video to multiple separate encoder processes in order to efficiently make use of all available CPU cores.

  


  The FFmpeg wiki article on Creating multiple outputs has this note from @rogerdpack :

  


  


  Outputting and re encoding multiple times in the same FFmpeg process will typically slow down to the "slowest encoder" in your list. Some encoders (like libx264) perform their encoding "threaded and in the background" so they will effectively allow for parallel encodings, however audio encoding may be serial and become the bottleneck, etc. It seems that if you do have any encodings that are serial, it will be treated as "real serial" by FFmpeg and thus your FFmpeg may not use all available cores. One work around to this is to use multiple ffmpeg instances running in parallel, or possible piping from one ffmpeg to another to "do the second encoding" etc. Or if you can avoid the limiting encoder (ex : using a different faster one [ex : raw format] or just doing a raw stream copy) that might help.

  


  


  The article has an example of using a tee pseudo-muxer, but it uses "a single instance of FFmpeg. The example of piping from one instance of FFmpeg to another only allows one encoder process.

  


  A 10-year-old version of the same article mentions using the tee process but it was subsequently deleted :

  


  


  Another option is to output from FFmpeg to "-" then to pipe that to a "tee" command, which can send it to multiple other processes, for instance 2 different other ffmpeg processes for encoding (this may save time, as if you do different encodings, and do the encoding in 2 different simultaneous processes, it might do encoding more in parallel than elsewise). Un benchmarked, however.

  


  


  Along the same lines : Some of the example commands use the mpegts to encapsulate frames before passing them between processes. Is there any constraint that this applies to the codecs or types of metadata that can be sent to downstream processes ?

  


• How to capture movie with Gphoto2 + ffmpeg and redirect serve to html embed

  1er avril 2021, par Doglas Antonio Dembogurski Fei

  Iam trying to capture video from Panasonic DC-GH5 camera to serve this and access from browser withoud ffserver because ffserver is deprecated

  


  Iam using Ubuntu 20.04

  


  #gphoto2 -v


gphoto2         2.5.23         gcc, popt(m), exif, cdk, aa, jpeg, readline
libgphoto2      2.5.25         standard camlibs (SKIPPING lumix), gcc, ltdl, EXIF
libgphoto2_port 0.12.0         iolibs: disk ptpip serial usb1 usbdiskdirect usbscsi, gcc, ltdl, EXIF, USB, serial without locking


  


  Iam try this code

  


  ffmpeg -f video4linux2 -s 640x480 -r 30 -i /dev/video0 -thread_queue_size 512 -ac 1 -f alsa -i pulse -f webm -listen 1 -seekable 0 -multiple_requests 1 http://localhost:8090


  


  and embed

  


  <video src="http://localhost:8090"></video>&#xA;

  


  in index.php but don`t appear anything.
If anyone knows a way to make a server for a specific port I would appreciate it
Thank you.

  


• Dreamcast Development Desktop

  28 mars 2011, par Multimedia Mike — Sega Dreamcast

  Some people are curious about what kind of equipment is required to program a Sega Dreamcast. This is my setup :

  
  
  

  It’s a bit overcomplicated. The only piece in that picture which doesn’t play a role in the Dreamcast development process is the scanner. The Eee PC does the heavy lifting of development (i.e., text editing and cross compilation) and uploads to the Dreamcast via a special serial cable. Those are the most essential parts and are really the only pieces necessary for a lot of algorithmic stuff (things that can be validated via a serial console). But then I have to go up a level where I output video. That’s where things get messy.

  
  
  

  The Mac Mini and giant monitor really just act as a glorified TV in this case. Ideally, it will be more than that. The DC outputs audio and video via composite cables to a Canopus DV capture bridge. That’s connected via FireWire to the external hard drive underneath the Mac Mini, which is connected to the Mac. Adobe Premiere Pro handles the DV capture / display.

  One day I hope to have something worthwhile to capture.