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Why So Slow?

Discussion in 'TiVo Stream' started by geekmedic, Mar 4, 2013.

  1. geekmedic

    geekmedic TiVo Fanatic TCF Club

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    Apr 4, 2003
    Atlanta, GA USA
    I finally purchased a Steam so I could stream recordings to my iPad (and download them for road trips).

    I have a MoCA network set up. I can't figure out why it takes 15-20 minutes to transfer a program on my own network when I can download the same show from iTunes in only 10 minutes?

    My network is much faster than my cable modem. Does the Stream impose limits on transfer speeds? I'm sure there is a reason why transfers are so slow.
     
  2. mattack

    mattack Active Member

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    Apr 9, 2001
    sunnyvale
    Note it takes about the same amount of time (approx - someone please correct me if I'm wildly off, but I don't think I am) if you download shows to a computer. That's why there is the Tivo Stream IMHO, to offload some of the 'hard work' to the stream.

    For one thing, I suspect if you download the same show from iTunes it will be MPEG 4, and not MPEG 2.. So it will be MUCH SMALLER, thus taking less time to download. If you're recording in HD on the Tivo, the file is PROBABLY (total wild guess) at least 2x as big.

    Also, at least for computer downloads, and I'm not sure if the Stream is different in this issue, the downloads aren't "just download the raw bits from the Tivo". They're unencrypted on the fly. The Tivo Stream *also* reformats them for the iPad on the fly, but it has hardware to do that faster than real time, so AFAIK, the raw transfer time is still the bottleneck.
     
  3. BigJimOutlaw

    BigJimOutlaw Active Member

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    Mar 21, 2004
    The Stream is transcoding the video -- it's converting it from MPEG2 into h.264 so that it can be played on the iPad. 15-20 minutes will be fairly typical.
     
  4. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    Nevada
    Actually the fact that it can transcode 4 HD streams at once, at 15-20 minutes per hour, is pretty impressive. A top of the line PC couldn't even do that. (not 4 at a time anyway)

    And the advantage over iTunes.... Using the Stream is essentially free, compared to $3 an episode from iTunes. At $3/ea the stream will pay for itself after you download 44 shows. :)
     
  5. mattack

    mattack Active Member

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    Apr 9, 2001
    sunnyvale
    Yes, but it is transcoding FASTER than realtime, right? I think the download speed is still the bottleneck.
     
  6. BigJimOutlaw

    BigJimOutlaw Active Member

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    Mar 21, 2004
    Faster than realtime of the show, yes. I don't know the specific theoretical fps encoding performance of the Stream. There are a number of variables.

    I just transferred a 1 hour HD show (7 GB) premiere-to-premiere over moca in 14 minutes.

    I then copied it to my ipod in 34 minutes. (960x540, best quality, 1 GB.)

    So in my scenario the Stream was less than half as fast as a raw transfer. We were always told we could expect roughly 2x the speed of realtime for the Stream, so that's pretty much right on.
     
  7. tre74

    tre74 Member

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    Nov 11, 2010
    I'm wondering if transfer times will improve with the next generation TiVo box if it gets a gigabit connection like the Stream. Am I wrong in thinking that the Stream is trying to pull data from the TiVo Premiere faster that it can send it out?
     
  8. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    I don't think that's the bottle neck. According to Jim's experiment the TiVo can send a recording to another TiVo in about 14 minutes but still takes 34 minutes to copy to the iPad. The bottle neck here appears to be the encoding.

    Now I guess it's possible that the next gen TiVo might have Stream capabilities built in and it could use a faster processor then the one in the standalone stream. But I doubt it. If anything it'll likely be a little slower then the current Stream. The Stream uses a pretty high end chip for the recoding. The next gen TiVo will likely use one of the SOC solutions from Broadcom. It'll be fast enough to do streaming, but it may not be much faster then real time when doing transfers.
     
  9. Philmatic

    Philmatic Member

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    Sep 17, 2003
    It may seem slow, but considering what's happening under the hood, the TiVo Stream is an amazing device running extremely efficient software and hardware and is faster than any other similarly priced hardware based video transcoder.

    I am still in shock that the TiVo Stream is a real shipping product that works as designed and requires no monthly fees. It's like we were put in a bizarro world.

    Also to answer your initial question. Downloading from iTunes is simply copying an already encoded file to your computer. The bottleneck with the stream is that it is encoding the video live from MPEG 2 which is the native broadcast and cable TV format to MPEG 4. MPEG 4 is extremely efficient in compressing video, but getting video converted TO MPEG 4 is extremely expensive (computer resources).

    You can question TiVo's decision to live convert video on the fly to iPads instead of encoding them ahead of time and storing them on the TiVo in a single MPEG 4 file, but this is likely the most efficient way to move forward without requiring too much work changing the core TiVo experience.
     

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