QUESTION: How does Invidious handle video streams?

[pluja]

I'm working on a project and I want to know how does Invidious handle the video streaming without making any connection to googlevideo from the client. Is it streaming the video through the invidious server to the client? If so, how is it done?

I have taken a look to the code, but I don't really undestand the structure and I've never worked with Crystal nor Ruby on rails so it's a bit slow for me. I can read and investigate the part of the code that is doing that if you can tell me where it is.

Thanks!

[isaackd]

I may be mistaken but it seems like these would be the relevant lines:

invidious/src/invidious.cr

Lines 5376 to 5597 in 62f015f

	get "/videoplayback/*" do |env|
	path = env.request.path
	path = path.lchop("/videoplayback/")
	path = path.rchop("/")
	path = path.gsub(/mime\/\w+\/\w+/) do |mimetype|
	mimetype = mimetype.split("/")
	mimetype[0] + "/" + mimetype[1] + "%2F" + mimetype[2]
	end
	path = path.split("/")
	raw_params = {} of String => Array(String)
	path.each_slice(2) do |pair|
	key, value = pair
	value = URI.decode_www_form(value)
	if raw_params[key]?
	raw_params[key] << value
	else
	raw_params[key] = [value]
	end
	end
	query_params = HTTP::Params.new(raw_params)
	env.response.headers["Access-Control-Allow-Origin"] = "*"
	env.redirect "/videoplayback?#{query_params}"
	end
	get "/videoplayback" do |env|
	query_params = env.params.query
	fvip = query_params["fvip"]? || "3"
	mns = query_params["mn"]?.try &.split(",")
	mns ||= [] of String
	if query_params["region"]?
	region = query_params["region"]
	query_params.delete("region")
	end
	if query_params["host"]? && !query_params["host"].empty?
	host = "https://#{query_params["host"]}"
	query_params.delete("host")
	else
	host = "https://r#{fvip}---#{mns.pop}.googlevideo.com"
	end
	url = "/videoplayback?#{query_params.to_s}"
	headers = HTTP::Headers.new
	REQUEST_HEADERS_WHITELIST.each do |header|
	if env.request.headers[header]?
	headers[header] = env.request.headers[header]
	end
	end
	client = make_client(URI.parse(host), region)
	response = HTTP::Client::Response.new(500)
	error = ""
	5.times do
	begin
	response = client.head(url, headers)
	if response.headers["Location"]?
	location = URI.parse(response.headers["Location"])
	env.response.headers["Access-Control-Allow-Origin"] = "*"
	host = "#{location.scheme}://#{location.host}"
	client = make_client(URI.parse(host), region)
	url = "#{location.full_path}&host=#{location.host}#{region ? "&region=#{region}" : ""}"
	else
	break
	end
	rescue Socket::Addrinfo::Error
	if !mns.empty?
	mn = mns.pop
	end
	fvip = "3"
	host = "https://r#{fvip}---#{mn}.googlevideo.com"
	client = make_client(URI.parse(host), region)
	rescue ex
	error = ex.message
	end
	end
	if response.status_code >= 400
	env.response.status_code = response.status_code
	env.response.content_type = "text/plain"
	next error
	end
	if url.includes? "&file=seg.ts"
	if CONFIG.disabled?("livestreams")
	env.response.status_code = 403
	error_message = "Administrator has disabled this endpoint."
	next templated "error"
	end
	begin
	client = make_client(URI.parse(host), region)
	client.get(url, headers) do |response|
	response.headers.each do |key, value|
	if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase)
	env.response.headers[key] = value
	end
	end
	env.response.headers["Access-Control-Allow-Origin"] = "*"
	if location = response.headers["Location"]?
	location = URI.parse(location)
	location = "#{location.full_path}&host=#{location.host}"
	if region
	location += "&region=#{region}"
	end
	next env.redirect location
	end
	IO.copy(response.body_io, env.response)
	end
	rescue ex
	end
	else
	if query_params["title"]? && CONFIG.disabled?("downloads") ||
	CONFIG.disabled?("dash")
	env.response.status_code = 403
	error_message = "Administrator has disabled this endpoint."
	next templated "error"
	end
	content_length = nil
	first_chunk = true
	range_start, range_end = parse_range(env.request.headers["Range"]?)
	chunk_start = range_start
	chunk_end = range_end
	if !chunk_end || chunk_end - chunk_start > HTTP_CHUNK_SIZE
	chunk_end = chunk_start + HTTP_CHUNK_SIZE - 1
	end
	client = make_client(URI.parse(host), region)
	# TODO: Record bytes written so we can restart after a chunk fails
	while true
	if !range_end && content_length
	range_end = content_length
	end
	if range_end && chunk_start > range_end
	break
	end
	if range_end && chunk_end > range_end
	chunk_end = range_end
	end
	headers["Range"] = "bytes=#{chunk_start}-#{chunk_end}"
	begin
	client.get(url, headers) do |response|
	if first_chunk
	if !env.request.headers["Range"]? && response.status_code == 206
	env.response.status_code = 200
	else
	env.response.status_code = response.status_code
	end
	response.headers.each do |key, value|
	if !RESPONSE_HEADERS_BLACKLIST.includes?(key.downcase) && key.downcase != "content-range"
	env.response.headers[key] = value
	end
	end
	env.response.headers["Access-Control-Allow-Origin"] = "*"
	if location = response.headers["Location"]?
	location = URI.parse(location)
	location = "#{location.full_path}&host=#{location.host}#{region ? "&region=#{region}" : ""}"
	env.redirect location
	break
	end
	if title = query_params["title"]?
	# https://blog.fastmail.com/2011/06/24/download-non-english-filenames/
	env.response.headers["Content-Disposition"] = "attachment; filename=\"#{URI.encode_www_form(title)}\"; filename*=UTF-8''#{URI.encode_www_form(title)}"
	end
	if !response.headers.includes_word?("Transfer-Encoding", "chunked")
	content_length = response.headers["Content-Range"].split("/")[-1].to_i64
	if env.request.headers["Range"]?
	env.response.headers["Content-Range"] = "bytes #{range_start}-#{range_end || (content_length - 1)}/#{content_length}"
	env.response.content_length = ((range_end.try &.+ 1) || content_length) - range_start
	else
	env.response.content_length = content_length
	end
	end
	end
	proxy_file(response, env)
	end
	rescue ex
	if ex.message != "Error reading socket: Connection reset by peer"
	break
	else
	client = make_client(URI.parse(host), region)
	end
	end
	chunk_start = chunk_end + 1
	chunk_end += HTTP_CHUNK_SIZE
	first_chunk = false
	end
	end
	end

This comment might also be helpful: #453 (comment)