d7d3439d79
Generate smart previews as .png so we don't suffer recompression losses when we convert the preview frame from a full size image down to a 150x150 .jpg thumbnail.
75 lines
1.8 KiB
Ruby
75 lines
1.8 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_channels.first[:width]
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end
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def height
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video_channels.first[:height]
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end
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def duration
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metadata.dig(:format, :duration).to_f
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end
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def video_channels
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metadata[:streams].select { |stream| stream[:codec_type] == "video" }
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end
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def audio_channels
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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_channels.present?
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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
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end
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