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• ffmpeg / video processing : make video repeat itself without duplicating content ?

  31 mars 2022, par RocketNuts

  Suppose I have a video file that is 20 MB in size and lasts 30 seconds.

  


  I want to create a new video file that basically consists of the existing video, repeated 10 times. So the new video should last 300 seconds (5 minutes) and contain the same content every 30 seconds.

  


  I could of course append this video to itself 10 times, resulting in a file of approximately 200 MB. But this seems very redundant, since obviously the same content is in there tenfold. I was hoping for a somewhat more intelligent approach, where the same 30 seconds of video is somehow 'referenced' 10 times over.

  


  Do common encoders or container formats (say h.264 in a .mp4 or .mkv container) support this ? And by any chance is there a way to pull this off with ffmpeg ?

  


• How to put a video inside a frame and record whole thing as a video ?

  7 octobre 2024, par crysis

  I have a video. I want to create a new video such that the video plays inside a frame similar to this screenshot. Loom recording does this. Most of the screen recorders do this.

  


  

  


  This screenshot is of the video. This is done in most of the screen recorders. Here is what I'm thinking

  


  

  • render video on a canvas with the background.

  


  • Play the video

  


  • Use mediarecorder API to record a new video.

  


  


  I don't have good understanding of frontend development. Is that how it is generally done or I need to use ffmpeg ? I would really appreciate any guidance here.

  


• ffmpeg configuration difficulty with filter_complex and hls

  4 février 2020, par akc42

  I am trying to set up ffmpeg so that it will record from a microphone and encode the results at the same time into a .flac file for later syncing up with some video I will be making.

  The microphone is plugged into a raspberry pi (4B) and I am currently trying it with a blue yeti mic, but I think I can do the same with a focusrite scarlett 2i2 plugged in instead. However I was puzzling about how to start the server recording and decided I could do it from a web browser if I made a simple nodejs server that spawned ffmpeg as a child process.

  But then I was inspired by this sample ffmpeg command which displays (on my desktop with an graphical interface) a volume meter

  ffmpeg -hide_banner -i 'http://distribution.bbb3d.renderfarming.net/video/mp4/bbb_sunflower_1080p_30fps_normal.mp4' -filter_complex "showvolume=rate=25:f=0.95:o=v:m=p:dm=3:h=80:w=480:ds=log:s=2" -c:v libx264 -c:a aac -f mpegts - | ffplay -window_title "Peak Volume" -i -

  What if I could stream the video produced by the showvolume filter to the web browser that I am using to control the ffmpeg process (NOTE I don’t want to send the audio with this). So I tried to read up on hls (since the control device will be an ipad - in fact that is what I will record the video on), and came up with this command

  ffmpeg -hide_banner -f alsa -ac 2 -ar 48k -i hw:CARD=Microphone -filter_complex "asplit=2[main][vol],[vol]showvolume=rate=25:f=0.95:o=v:m=p:dm=3:h=80:w=480:ds=log:s=2[vid]" -map [main] -c:a:0 flac recordings/session_$(date +%a_%d_%b_%Y___%H_%M_%S).flac -map [vid] -preset veryfast -g 25 -an -sc_threshold 0 -c:v:1 libx264 -b:v:1 2000k -maxrate:v:1 2200k -bufsize:v:3000k -f hls -hls_time 4 -hls_flags independent_segments delete_segments -strftime 1 -hls_segment_filename recordings/volume-%Y%m%d-%s.ts recordings/volume.m3u8

  The problem is I am finding the documentation a bit opaque as to what happens once I have generated two streams - the main audio and a video stream, and this command throws both a warning and an error :-

  The warning is Guessed Channel Layout for Input Stream #0.0 : stereo

  and the error is

  [NULL @ 0x1baa130] Unable to find a suitable output format for 'hls'
  
  hls: Invalid argument

  What I am trying to do is set up stream labels [main] and [vol] as I split the incoming audio into two parts, then I pass [vol] through the "showvolume" filter and end up with stream [vid].

  I think I need to then use -map to specify encoding the [main] stream down to flac and writing it out to file (The file exists after I run the command although they have zero length), and use another -map to pass through to the -f hls section. But I think I have something wrong at this stage.

  Can someone help me get this command right.