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DEF CON 17 Audio and Video now available!

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  • #31
    Re: DEF CON 17 Audio and Video now available!

    Originally posted by Deviant Ollam View Post
    oh, and thanks for the good explanation about HTTP transfer standards, cot!
    Thanks. :-)

    Originally posted by Dark Tangent View Post
    I'll check into content-length to make sure there is no strange stripping going on. Thanks Cot! you rule.
    I had another thought on what could cause the length to be removed:

    If there is a filter between the server and the client that is compressing (or trying to compress) the video, audio, rar-files, iso, etc., then it would also, likely, compress content as a stream, and as a result, not have a total size of content being transmitted over http/https before it starts transmitting it. (Again, for efficiency, the server would not want to pre-compress and store an entire file before transmitting it.)

    Usually, when compression is enabled for web servers to web browsers, a selection list of either extensions or MIME-types is provided to either specify:
    * Items that should be compressed, with default compression disabled (or)
    * What should NOT be compressed, with everything else being compressed.

    Most of the time, web and network admins will disable compression for any 8-bit content, but leave it enabled for 7-bit content (as text such as .txt, .html, .js, and css.) This is especially important when looking to serve video, which is usually compressed with much *better compression than an inline gzip compression done with an emphasis for speed and low CPU use.

    But is this the case?

    wget --header="accept-encoding: gzip" http://media.defcon.org/dc-17/video/...d%20Slides.m4v

    vs.

    wget http://media.defcon.org/dc-17/video/...d%20Slides.m4v

    And, what-do-you-know? When I specify compression as "ok" with wget, I get no time estimate for when it will be completed, but when I don't support compression, I see a time estimate.

    Solution? Disable compression for 8-bit content, or at least for video, and audio, because you are probably not saving much, but you are taxing your CPU more than you need to.

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    • #32
      Re: DEF CON 17 Audio and Video now available!

      As of tonight, I'm experiencing the same issue as before - no communication at all with the download server. no ACK.
      It's not stupid, it's advanced.

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