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Rewrite transcript logic to be more generic
The transcript logic in Invidious was written specifically as a workaround for captions, and not transcripts as a feature. This commit genericises the logic a bit as so it can be used for implementing transcripts within Invidious' API and UI as well. The most notable change is the added parsing of section headings when it was previously skipped over in favor of regular lines.
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@ -89,9 +89,14 @@ module Invidious::Routes::API::V1::Videos
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if CONFIG.use_innertube_for_captions
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params = Invidious::Videos::Transcript.generate_param(id, caption.language_code, caption.auto_generated)
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initial_data = YoutubeAPI.get_transcript(params)
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webvtt = Invidious::Videos::Transcript.convert_transcripts_to_vtt(initial_data, caption.language_code)
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transcript = Invidious::Videos::Transcript.from_raw(
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YoutubeAPI.get_transcript(params),
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caption.language_code,
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caption.auto_generated
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)
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webvtt = transcript.to_vtt
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else
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# Timedtext API handling
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url = URI.parse("#{caption.base_url}&tlang=#{tlang}").request_target
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@ -1,8 +1,21 @@
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module Invidious::Videos
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# Namespace for methods primarily relating to Transcripts
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module Transcript
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record TranscriptLine, start_ms : Time::Span, end_ms : Time::Span, line : String
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# A `Transcripts` struct encapsulates a sequence of lines that together forms the whole transcript for a given YouTube video.
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# These lines can be categorized into two types: section headings and regular lines representing content from the video.
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struct Transcript
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# Types
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record HeadingLine, start_ms : Time::Span, end_ms : Time::Span, line : String
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record RegularLine, start_ms : Time::Span, end_ms : Time::Span, line : String
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alias TranscriptLine = HeadingLine | RegularLine
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property lines : Array(TranscriptLine)
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property language_code : String
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property auto_generated : Bool
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# Initializes a new Transcript struct with the contents and associated metadata describing it
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def initialize(@lines : Array(TranscriptLine), @language_code : String, @auto_generated : Bool)
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end
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# Generates a protobuf string to fetch the requested transcript from YouTube
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def self.generate_param(video_id : String, language_code : String, auto_generated : Bool) : String
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kind = auto_generated ? "asr" : ""
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@ -30,48 +43,57 @@ module Invidious::Videos
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return params
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end
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def self.convert_transcripts_to_vtt(initial_data : Hash(String, JSON::Any), target_language : String) : String
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# Convert into array of TranscriptLine
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lines = self.parse(initial_data)
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# Constructs a Transcripts struct from the initial YouTube response
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def self.from_raw(initial_data : Hash(String, JSON::Any), language_code : String, auto_generated : Bool)
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body = initial_data.dig("actions", 0, "updateEngagementPanelAction", "content", "transcriptRenderer",
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"content", "transcriptSearchPanelRenderer", "body", "transcriptSegmentListRenderer",
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"initialSegments").as_a
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lines = [] of TranscriptLine
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body.each do |line|
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if unpacked_line = line["transcriptSectionHeaderRenderer"]?
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line_type = HeadingLine
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else
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unpacked_line = line["transcriptSegmentRenderer"]
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line_type = RegularLine
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end
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start_ms = unpacked_line["startMs"].as_s.to_i.millisecond
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end_ms = unpacked_line["endMs"].as_s.to_i.millisecond
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text = extract_text(unpacked_line["snippet"]) || ""
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lines << line_type.new(start_ms, end_ms, text)
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end
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return Transcript.new(
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lines: lines,
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language_code: language_code,
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auto_generated: auto_generated,
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)
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end
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# Converts transcript lines to a WebVTT file
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#
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# This is used within Invidious to replace subtitles
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# as to workaround YouTube's rate-limited timedtext endpoint.
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def to_vtt
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settings_field = {
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"Kind" => "captions",
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"Language" => target_language,
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"Language" => @language_code,
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}
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# Taken from Invidious::Videos::Captions::Metadata.timedtext_to_vtt()
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vtt = WebVTT.build(settings_field) do |vtt|
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lines.each do |line|
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@lines.each do |line|
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# Section headers are excluded from the VTT conversion as to
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# match the regular captions returned from YouTube as much as possible
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next if line.is_a? HeadingLine
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vtt.cue(line.start_ms, line.end_ms, line.line)
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end
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end
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return vtt
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end
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private def self.parse(initial_data : Hash(String, JSON::Any))
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body = initial_data.dig("actions", 0, "updateEngagementPanelAction", "content", "transcriptRenderer",
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"content", "transcriptSearchPanelRenderer", "body", "transcriptSegmentListRenderer",
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"initialSegments").as_a
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lines = [] of TranscriptLine
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body.each do |line|
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# Transcript section headers. They are not apart of the captions and as such we can safely skip them.
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if line.as_h.has_key?("transcriptSectionHeaderRenderer")
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next
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end
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line = line["transcriptSegmentRenderer"]
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start_ms = line["startMs"].as_s.to_i.millisecond
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end_ms = line["endMs"].as_s.to_i.millisecond
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text = extract_text(line["snippet"]) || ""
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lines << TranscriptLine.new(start_ms, end_ms, text)
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end
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return lines
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end
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end
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end
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