8b3ab04724
Fix how the duration of videos and animated GIFs / PNGs is calculated. If we can't determine the duration from the file metadata, then play the entire video or animation back using FFmpeg and scrape the duration and frame count. This is necessary for things like WebM files where the duration metadata is optional, or animated GIFs and PNGs that don't have a duration field in the metadata, only a frame count and a sequence of frame delays.
114 lines
3.4 KiB
Ruby
114 lines
3.4 KiB
Ruby
require "shellwords"
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# A wrapper for the ffmpeg command.
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class FFmpeg
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extend Memoist
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class Error < StandardError; end
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attr_reader :file
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# Operate on a file with FFmpeg.
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# @param file [File, String] a webm, mp4, gif, or apng file
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def initialize(file)
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@file = file.is_a?(String) ? File.open(file) : file
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end
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# Generate a .png preview image for a video or animation. Generates
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# thumbnails intelligently by avoiding blank frames.
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#
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# @return [MediaFile] the preview image
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def smart_video_preview
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vp = Tempfile.new(["video-preview", ".png"], binmode: true)
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# https://ffmpeg.org/ffmpeg.html#Main-options
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# https://ffmpeg.org/ffmpeg-filters.html#thumbnail
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output = shell!("ffmpeg -i #{file.path.shellescape} -vf thumbnail=300 -frames:v 1 -y #{vp.path.shellescape}")
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Rails.logger.debug(output)
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MediaFile.open(vp)
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end
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# Get file metadata using ffprobe.
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# @see https://ffmpeg.org/ffprobe.html
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# @see https://gist.github.com/nrk/2286511
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# @return [Hash] a hash of the file's metadata
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def metadata
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output = shell!("ffprobe -v quiet -print_format json -show_format -show_streams #{file.path.shellescape}")
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json = JSON.parse(output)
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json.with_indifferent_access
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end
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def width
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video_streams.first[:width]
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end
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def height
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video_streams.first[:height]
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end
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# @see https://trac.ffmpeg.org/wiki/FFprobeTips#Duration
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# @return [Float, nil] The duration of the video or animation in seconds, or nil if unknown.
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def duration
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if metadata.dig(:format, :duration).present?
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metadata.dig(:format, :duration).to_f
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elsif playback_info.has_key?(:time)
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hours, minutes, seconds = playback_info[:time].split(/:/)
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hours.to_f*60*60 + minutes.to_f*60 + seconds.to_f
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else
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nil
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end
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end
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# @return [Integer, nil] The number of frames in the video or animation, or nil if unknown.
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def frame_count
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if video_streams.first.has_key?(:nb_frames)
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video_streams.first[:nb_frames].to_i
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elsif playback_info.has_key?(:frame)
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playback_info[:frame].to_i
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else
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nil
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end
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end
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# @return [Float, nil] The average frame rate of the video or animation, or nil if unknown.
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def frame_rate
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return nil if frame_count.nil? || duration.nil? || duration == 0
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frame_count / duration
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end
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def video_streams
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metadata[:streams].select { |stream| stream[:codec_type] == "video" }
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end
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def audio_streams
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metadata[:streams].select { |stream| stream[:codec_type] == "audio" }
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end
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def has_audio?
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audio_streams.present?
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end
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# Decode the full video and return a hash containing the frame count, fps, and runtime.
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def playback_info
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output = shell!("ffmpeg -i #{file.path.shellescape} -f null /dev/null")
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status_line = output.lines.grep(/\Aframe=/).first.chomp
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# status_line = "frame= 10 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.48 bitrate=N/A speed= 179x"
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# info = {"frame"=>"10", "fps"=>"0.0", "q"=>"-0.0", "Lsize"=>"N/A", "time"=>"00:00:00.48", "bitrate"=>"N/A", "speed"=>"188x"}
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info = status_line.scan(/\S+=\s*\S+/).map { |pair| pair.split(/=\s*/) }.to_h
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info.with_indifferent_access
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rescue Error => e
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{}
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end
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def shell!(command)
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program = command.shellsplit.first
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output, status = Open3.capture2e(command)
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raise Error, "#{program} failed: #{output}" if !status.success?
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output
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end
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memoize :metadata, :playback_info, :frame_count, :duration
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end
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