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• Adding a text overlay with constant size to a video with varying resolutions using ffmpeg

  22 December 2020, by BetaLixT

  I have a video with different resolutions at different points of the video and need to add a text overlay to it. I'm new with ffmpeg, the following is one of the commands I've tried

  


  ffmpeg -i input.mp4 -vf "drawtext=text='Hello World'" -c:a copy output.mp4


  


  But the output has blurry text with it resizing every few seconds (I'm guessing because of the various resolutions in the video) and some parts of the video have their aspect ratios altered.

  


  Information on input file

  


  The input.mp4 video is generated from some .h264 raw data converted to mp4 and some blank mp4 generated that are all concatenated together, following are the commands

  


  h264 to mp4:

  


  ffmpeg a.h264 -c copy a.mp4


  


  blank mp4

  


  ffmpeg -t 5 -f lavfi -i color=c=black:s=200x200 -c:v libx264 -tune stillimage -pix_fmt yuv420p -video_track_timescale 1200000 b.mp4


  


  Concat:

  


  ffmpeg -safe 0 -f concat -i list.txt -s 720x960 -c copy input.mp4


  


  I'd be thankful for any advice on how I could achieve this

  


• Ffmpeg - Generate VTT File From Sprite, Using Spatial Media Fragment

  20 October 2019, by David

  Hi I am looking to create a .VTT file from a sprite that i have generated using Ffmpeg.

  Ffmpeg command:

   $"-i {inputMediaFile} -vf \"select = not(mod(n\\, 30)),scale = 120:80,tile = 7x7\" -an -vsync 0 {outputMediaFile}"

  This selects every 30th frame, and then scales it to 120x80 pixels and creates 8x8 tiles in the output image.

  I would like to make a .VTT from the generated image in C#, so i know the height and width of my individual images in the sprite (120x80) and there is 64 images in total in the output image.

  From this i need to produce a VTT like this:

  WEBVTT
  
  
  
  1
  
  00:00:00.000 --> 00:00:01.000
  
  test-00001.jpg#xywh=0,0,120,80
  
  
  
  2
  
  00:00:01.000 --> 00:00:02.000
  
  test-00001.jpg#xywh=120,0,120,80
  
  
  
  3
  
  00:00:02.000 --> 00:00:03.000
  
  test-00001.jpg#xywh=240,0,120,80
  
  
  
  4
  
  00:00:03.000 --> 00:00:04.000
  
  test-00001.jpg#xywh=360,0,120,80
  
  
  
  5
  
  00:00:04.000 --> 00:00:05.000
  
  test-00001.jpg#xywh=480,0,120,80
  
  
  
  6
  
  00:00:05.000 --> 00:00:06.000
  
  test-00001.jpg#xywh=600,0,120,80
  
  
  
  7
  
  00:00:06.000 --> 00:00:07.000
  
  test-00001.jpg#xywh=720,0,120,80
  
  
  
  8
  
  00:00:07.000 --> 00:00:08.000
  
  test-00001.jpg#xywh=840,0,120,80
  
  
  
  9
  
  00:00:08.000 --> 00:00:09.000
  
  test-00001.jpg#xywh=0,80,120,80

  There is also situations when there is n amount of sprite files.

  Im hoping there may be a library out there that can handle this, or even better if i can keep it contained within Ffmpeg - based on Ffmpeg docs i dont think this is possible though.

  Thanks in advance if anyone as any ideas, its doable as ive seen Nodejs and Ruby examples.

• MSE Does not show duration when MPEG-DASH segments are created with FFmpeg

  15 March 2023, by WaveLink

  I am trying to create a system that streams DASH segments to the browser, where it gets decoded by Media Source Extensions. When using MP4Box, the init segment loads the duration into the player, but the version generated by FFmpeg does not.

  


  I believe this is due to some sort of header missing from the init segment generated by FFmpeg, but I have not been able to figure it out. Here is the command I use to generate the files:

  


  ffmpeg -i .\source.opus -c:a libopus -c:v none -seg_duration 1 -dash_segment_type mp4 -preset ultrafast -use_timeline 1 -use_template 1 -streaming 1 -init_seg_name "segment_init.mp4" -media_seg_name "segment_$Number$.m4s" -fflags +genpts -f dash ./out.mpd
When using MP4Box, this is the config I use:

  


  MP4Box -dash 1000 -rap -profile live -segment-name "segment_$Number" .\out.mp4
In both cases, the audio does play, and both of them contain similar headers, but the FFmpeg version just does not contain the media duration in the init segment, or at least the MSE implementation cannot read it.

  


  I tested this in Chrome, Firefox, and Edge, and all of them behave the same.

  


  Thanks for any help.