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# frozen_string_literal: true
module ActiveStorage
# Extracts the following from a video blob:
#
# * Width (pixels)
# * Height (pixels)
# * Duration (seconds)
# * Angle (degrees)
# * Display aspect ratio
#
# Example:
#
# ActiveStorage::VideoAnalyzer.new(blob).metadata
# # => { width: 640.0, height: 480.0, duration: 5.0, angle: 0, display_aspect_ratio: [4, 3] }
#
# When a video's angle is 90 or 270 degrees, its width and height are automatically swapped for convenience.
#
# This analyzer requires the {FFmpeg}[https://www.ffmpeg.org] system library, which is not provided by Rails.
class Analyzer::VideoAnalyzer < Analyzer
def self.accept?(blob)
blob.video?
end
def metadata
{ width: width, height: height, duration: duration, angle: angle, display_aspect_ratio: display_aspect_ratio }.compact
end
private
def width
if rotated?
computed_height || encoded_height
else
encoded_width
end
end
def height
if rotated?
encoded_width
else
computed_height || encoded_height
end
end
def duration
Float(video_stream["duration"]) if video_stream["duration"]
end
def angle
Integer(tags["rotate"]) if tags["rotate"]
end
def display_aspect_ratio
if descriptor = video_stream["display_aspect_ratio"]
if terms = descriptor.split(":", 2)
numerator = Integer(terms[0])
denominator = Integer(terms[1])
[numerator, denominator] unless numerator == 0
end
end
end
def rotated?
angle == 90 || angle == 270
end
def computed_height
if encoded_width && display_height_scale
encoded_width * display_height_scale
end
end
def encoded_width
@encoded_width ||= Float(video_stream["width"]) if video_stream["width"]
end
def encoded_height
@encoded_height ||= Float(video_stream["height"]) if video_stream["height"]
end
def display_height_scale
@display_height_scale ||= Float(display_aspect_ratio.last) / display_aspect_ratio.first if display_aspect_ratio
end
def tags
@tags ||= video_stream["tags"] || {}
end
def video_stream
@video_stream ||= streams.detect { |stream| stream["codec_type"] == "video" } || {}
end
def streams
probe["streams"] || []
end
def probe
download_blob_to_tempfile { |file| probe_from(file) }
end
def probe_from(file)
IO.popen([ ffprobe_path, "-print_format", "json", "-show_streams", "-v", "error", file.path ]) do |output|
JSON.parse(output.read)
end
rescue Errno::ENOENT
logger.info "Skipping video analysis because FFmpeg isn't installed"
{}
end
def ffprobe_path
ActiveStorage.paths[:ffprobe] || "ffprobe"
end
end
end
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