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• Record and preview webcamera stream at the same time

  11 juin 2019, par Vlad Popov

  I’m using ffmpeg and Windows 7/10 OS and going to save webcamera stream to file and preview it at the same time (from time to time, not constantly).
  I can solve each of these tasks separately :

  1. Saving webcamera stream to 1-minute files :

  $ffmpeg_exe = "C:\ffmpeg.exe"

  $video_source = "USB Video Device"

  Start-Process $ffmpeg_exe -ArgumentList @("-y -hide_banner -f dshow -rtbufsize 100M -i video=``"$video_source``" -preset ultrafast -strftime 1 -f segment -segment_time 00:01:00 ``"$out_folder\%Y_%m_%d_%H_%M_%S.mp4``"") -Wait -NoNewWindow

  2. Preview webcamera using ffplay :

  $ffplay_exe = "C:\ffplay.exe"

  Start-Process $ffplay_exe -ArgumentList @("-hide_banner -f dshow -i video=``"$video_source``" -preset ultrafast") -Wait -NoNewWindow

  Is there a way to do it using single command ? I think I have to use ffmpeg within named pipes but I don’t understand how to create/operate them. Maybe someone have already working Windows command which will 1) save webcamera video to file 2) also send it to named pipe for another applications like ffplay or VLC ?

  Thanks for your answers,

  —Vlad

• FFMPEG - Getting consistent accurate video time segments

  10 juin 2020, par rossmcm

  I'm processing a large number of videos that need to be time-synchronized to match an audio track (it's a "virtual choir"-type project). I have tried several variations based on the contents of this post, but I get a variability of some seconds on the actual output files. The resulting segment length is variable, and the point in the input video that the output video begins is not at all accurate (I was expecting a +-1 frame error).

  



  Here's my attempt :

  



  :: Syntax:  GetSegment.bat <input file="file" /> <starting time="time" in="in" ms="ms"> <duration in="in" ms="ms">&#xA;:: Example: GetSegment.bat vid.mp4 10000 50000&#xA;::          would produce vid-keyed.mp4 and vid-segment.mp4&#xA;&#xA;@set "_VideoIn=%~1"&#xA;@set "_VideoOutKeyed=%~dpn1-keyed%~x1"&#xA;@set "_VideoOutSegment=%~dpn1-segment%~x1"&#xA;@set "_VideoStartms=%~2"&#xA;@set "_VideoLengthms=%~3"&#xA;@set /a _VideoEndms= %_VideoStartms% &#x2B; %_VideoLengthms%&#xA;ffmpeg -y -i "%_VideoIn%" -force_key_frames %_VideoStartms%ms,%_VideoEndms%ms "%_VideoOutKeyed%"&#xA;ffmpeg -y -ss  %_VideoStartms%ms -i "%_VideoOutKeyed%" -t %_VideoEndms%ms  -codec copy "%_VideoOutSegment%"  &#xA;@exit /b %errorlevel%&#xA;</duration></starting>

  


• Simultaneous Recording and Real-Time Display Using ffmpeg with DeckLink

  9 décembre 2023, par ark1974

  I am currently working with a DeckLink Duo card, specifically utilizing port 2. My objective is to use FFmpeg to ingest RAW HD SDI, save it as an MP4 file, and concurrently display the incoming SDI video on the computer screen in real-time.

  


  I have experimented with various FFmpeg command lines, combining decklink and sdl options, to achieve this dual functionality :

  


  ffmpeg -f decklink -i 'DeckLink Duo@2' -c:v libx264 -preset ultrafast -tune zerolatency -f sdl "My Screen"


  


  However, I am encountering challenges in achieving both recording and real-time display simultaneously.

  


  I would appreciate any insights, suggestions, or alternative approaches to enable the concurrent recording and display of SDI video using DeckLink with ffmpeg.