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copied!<p><strong>which Ruby version are you using?</strong></p> <p><strong>which ID3 Tag version are you trying to read?</strong></p> <p><strong>ID3v1 tags</strong> are at the end of a file, in the last 128 bytes. With Net::HTTP it doesn't seem to be possible to seek forward towards the end of the file and read only the last N bytes. If you try that, using <code>headers = {"Range" => "bytes=128-"}</code> , it always seems to download the complete file. <code>resp.body.size => file-size</code> . But no big loss, because <strong>ID3 version 1 is pretty much outdated at this point</strong> because of it's limitations, such as fixed length format, only ASCII text, ...). iTunes uses ID3 version 2.2.0.</p> <p><strong>ID3v2 tags</strong> are at the beginning of a file - to support streaming - you can download the initial part of the MP3 file, which contains the ID3v2 header, via HTTP protocol >= 1.1</p> <p><strong>The short answer:</strong></p> <pre><code>require 'net/http' require 'uri' require 'id3' # id3 RUby library require 'hexdump' file_url = 'http://example.com/filename.mp3' uri = URI(file_url) size = 1000 # ID3v2 tags can be considerably larger, because of embedded album pictures Net::HTTP.version_1_2 # make sure we use higher HTTP protocol version than 1.0 http = Net::HTTP.new(uri.host, uri.port) resp = http.get( file_url , {'Range' => "bytes=0-#{size}"} ) # should check the response status codes here.. if resp.body =~ /^ID3/ # we most likely only read a small portion of the ID3v2 tag.. # file has ID3v2 tag puts resp.body.hexdump tag2 = ID3::Tag2.new tag2.read_from_buffer( resp.body ) @id3_tag_size = tag2.ID3v2tag_size # that's the size of the whole ID3v2 tag # we should now re-fetch the tag with the correct / known size # ... end </code></pre> <p>e.g.:</p> <pre><code> index 0 1 2 3 4 5 6 7 8 9 A B C D E F 00000000 ["49443302"] ["00000000"] ["11015454"] ["3200000d"] ID3.......TT2... 00000010 ["004b6167"] ["75796120"] ["48696d65"] ["00545031"] .Kaguya Hime.TP1 00000020 ["00000e00"] ["4a756e6f"] ["20726561"] ["63746f72"] ....Juno reactor 00000030 ["0054414c"] ["00001100"] ["4269626c"] ["65206f66"] .TAL....Bible of 00000040 ["20447265"] ["616d7300"] ["54524b00"] ["00050036"] Dreams.TRK....6 00000050 ["2f390054"] ["59450000"] ["06003139"] ["39370054"] /9.TYE....1997.T 00000060 ["434f0000"] ["1300456c"] ["65637472"] ["6f6e6963"] CO....Electronic 00000070 ["612f4461"] ["6e636500"] ["54454e00"] ["000d0069"] a/Dance.TEN....i 00000080 ["54756e65"] ["73207632"] ["2e300043"] ["4f4d0000"] Tunes v2.0.COM.. 00000090 ["3e00656e"] ["67695475"] ["6e65735f"] ["43444442"] >.engiTunes_CDDB 000000a0 ["5f494473"] ["00392b36"] ["34374334"] ["36373436"] _IDs.9+647C46746 000000b0 ["38413234"] ["38313733"] ["41344132"] ["30334544"] 8A248173A4A203ED 000000c0 ["32323034"] ["4341422b"] ["31363333"] ["39390000"] 2204CAB+163399.. 000000d0 ["00000000"] ["00000000"] ["00000000"] ["00000000"] ................ </code></pre> <p><strong>The long answer looks something like this:</strong> (you'll need id3 library version 1.0.0_pre or newer)</p> <pre><code>require 'net/http' require 'uri' require 'id3' # id3 RUby library require 'hexdump' file_url = 'http://example.com/filename.mp3' def get_remote_id3v2_tag( file_url ) # you would call this.. id3v2tag_size = get_remote_id3v2_tag_size( file_url ) if id3v2tag_size > 0 buffer = get_remote_bytes(file_url, id3v2tag_size ) tag2 = ID3::Tag2.new tag2.read_from_buffer( buffer ) return tag2 else return nil end end private def get_remote_id3v2_tag_size( file_url ) buffer = get_remote_bytes( file_url, 100 ) if buffer.bytesize > 0 return buffer.ID3v2tag_size else return 0 end end private def get_remote_bytes( file_url, n) uri = URI(file_url) size = n # ID3v2 tags can be considerably larger, because of embedded album pictures Net::HTTP.version_1_2 # make sure we use higher HTTP protocol version than 1.0 http = Net::HTTP.new(uri.host, uri.port) resp = http.get( file_url , {'Range' => "bytes=0-#{size-1}"} ) resp_code = resp.code.to_i if (resp_code >= 200 && resp_code < 300) then return resp.body else return '' end end get_remote_id3v2_tag_size( file_url ) => 2262 </code></pre> <p>See:</p> <p><a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35" rel="nofollow noreferrer">http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35</a></p> <p><a href="http://en.wikipedia.org/wiki/Byte_serving" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Byte_serving</a></p> <p><strong>some examples how to download in parts files can be found here:</strong></p> <p>but please note that there seems to be no way to start downloading "in the middle"</p> <p><a href="https://stackoverflow.com/questions/2263540/how-do-i-download-a-binary-file-over-http-using-ruby">How do I download a binary file over HTTP?</a></p> <p><a href="http://unixgods.org/~tilo/Ruby/ID3/docs/index.html" rel="nofollow noreferrer">http://unixgods.org/~tilo/Ruby/ID3/docs/index.html</a></p>

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