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• Thumb image from video using streamio-ffmpeg gem without loosing aspect ratio and given size while uploading using carrierwave

  6 mars 2013, par Krishna

  I am working on a project which require user to upload video, While they upload the video I will be converting the video to flv and mp4 format, and I need to take 2 screenshots for thumb image.

  I am using streamio-ffmpeg gem and CarrierWave the code for video conversion is below.

  movie = FFMPEG::Movie.new(file_name)
  
  movie.transcode("output_mp4.mp4", "-sameq -s 640x480 -deinterlace -b 512000 -vol 320 -ar 44100 -r 25")           
  
  movie.transcode("output_flv.flv", "-deinterlace -qscale 1 -b 512000 -vol 320 -ar 44100 -r 25")  

  This will convert the video to mp4 and flv format.

  The below code is used for creating thumb image, but the images look like stretched since not maintaining the aspect-ratio.

    movie.screenshot("output_thumb1.jpg", :resolution => '40x40')         
  
    movie.screenshot("output_thumb2.jpg", :resolution => '80x80')       

  So after looking at streamio-ffmpeg gem documentation, I came up with this solution.

  movie.screenshot("output_thumb.jpg", { seek_time: 2, resolution: '80x80' }, preserve_aspect_ratio: :width, preserve_aspect_ratio: :height)

  This Will preserve the aspect ratio but the image size is changed, its not '80x80'.

  My requirement is I need a thumb image of size 80x80 but it should not look stretched

  I am actually looking for something similar to resize_and_pad which CarrierWave::RMagick have.

• Extract closed captions VTT from stream using ffmpeg

  15 avril 2021, par EK0

  I can extract closed caption information from an mp4 file using ffmpeg v. 3.4.7 thus :

  


  ffmpeg -f lavfi -i movie="sample.mp4[out+subcc]" -map 0:1 -c:s webvtt /tmp/output.vtt


  


  The file was obtained by capturing a live HLS stream containing closed captions. I would like to extract the closed captions directly from the stream, instead after storing the video in a file. I've tried various things, including :

  


  ffmpeg -f lavfi -i movie="http://example.com/stream.m3u8[out+subcc]" -map 0:0 -c:s webvtt /tmp/output.vtt


  


  But the movie filter does not recognize the URL, even though the ffmpeg filter documentation says that the file name for the movie filter is "not necessarily a file ; it can also be a device or a stream accessed through some protocol" :

  


  


  [Parsed_movie_0 @ 0x264ad80] Failed to avformat_open_input 'http'
  
[lavfi @ 0x2647e80] Error initializing filter 'movie' with args 'http://example.com/stream.m3u8' ;
  
movie=http://example.com/stream.m3u8[out+subcc] : No such file or directory

  


  


  When I capture the video form the stream like this :

  


  ffmpeg -i http://example.com/stream.m3u8 /tmp/output.mp4


  


  ffmpeg reports that the stream does contain closed captions (which is where the captured video file sample.mp4 got them) :

  


  


  Stream #0:0 : Video : h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, bt709), 480x270 [SAR 1:1 DAR 16:9], Closed Captions, 14.99 fps, 14.99 tbr, 90k tbn, 29.97 tbc

  


  


  Is it possible to do this ? Thanks for any pointers.

  


• ffmpeg not detecting trim frames edited by quicktime

  20 juillet 2016, par Andrew Sinagra

  I have an h264 that was trimmed using Quicktime 7 and exported as a new movie. Opening the movie in quicktime, the trimmed frames appear to no longer exist. However, when I convert the movie using ffmpeg the trimmed frames reappear. I also tried to grab a specific frame using -ss and the frame is incorrect as ffmpeg is not recognizing the trim and using in essence the wrong time.

  Is there a way to get ffmpeg to recognize the in/out points set by quicktime ?

  Additionally is there a way to read the in trim value and pass the offset time to ffmpeg ?