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video compression

Discussion in 'Off Topic' started by shark2k, Jan 18, 2009.

  1. shark2k

    shark2k Member

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    #1 shark2k, Jan 18, 2009
    Last edited: Jan 18, 2009
    I have my laptop set to power save mode (it's a dual core CPU) and I find playback is not necessarily smooth also. So I agree, do what doug said and let it fully load, but if the playback isn't smooth still, it could be your computer. When I put my computer on to "suck up electricity" mode and have the CPU run at full power it works better. Weird thing is I would think you wouldn't need so much power because the video is hosted on another computer? I still haven't figured that out (and I'm a computer nerd :tongue:).

    -Shark2k
     
  2. doug

    doug Administrator / Head Moderator

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    #2 doug, Jan 18, 2009
    Last edited: Jan 18, 2009
    Yeah, I actually started to type that the other issue could be a weak processor, but I figured TEG wouldn't have that problem. You're local processor has to do work to decode the video at a reasonable frame rate. If your laptop is on power save mode, it likely has fewer CPU cycles available.

    (Part of the reason these higher quality vids are available is that there are video codecs that allow for higher compression while maintaining good video quality at the cost of being more processor intensive.)
     
  3. TEG

    TEG TMC Moderator

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    I could probably bore you guys to tears talking about video compression.
    My computer is fast enough to play ATSC bandwidth 1080 MPEG2 (or other similar formats) when I have it locally on the hard disk. As far as Youtube is concerned it is just more data (a bigger file) they stream to you. They don't do any realtime decompression when you are playing it. It is just a matter of getting the data to me fast enough. Yes, if I let it buffer and download more to my computer first it helps, but I prefer to take advantage of real streaming and start watching right away.

    The problem for me is shared bandwidth on my home DSL.

    The power profile on some laptops will let Intel CPUs enable "speed step" technology to slow down the CPU to save power. I am using a desktop so I don't have that issue. By the way, SpeedStep is a bit goofy. You would think it would try to ensure full clockrate when you run CPU intensive applications, but from what I have seen it will sometimes slow you down when you really are trying to use your system. Again, that isn't my issue as I am using a desktop CPU which doesn't have SpeedStep. For laptop users you can switch to "always on" power profile.
     
  4. shark2k

    shark2k Member

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    #4 shark2k, Jan 18, 2009
    Last edited: Jan 18, 2009
    Thanks doug. I'm pretty sure what you said about "your" computer having to decode the video is what was tripping me up. Thinking back on it it makes sense that the local process would have to decode it, but I guess for some reason I was thinking it would be decoded from the server. Typing that now though, that seems really stupid because of the amount of bandwidth that would be required to transmit that.

    TEG, as to boring us (well at least me) to tears about video compression, that stuff actually really interests me and I would have no problem reading about it if you actually know what you are talking about. Of course, depending on how technical you get, my eyes might start to roll back in their sockets from confusing, but I would be interested nonetheless :biggrin:. I'm a computer geek (self-proclaimed) and really enjoy learning more about that stuff.

    Ok, that was all pointless, but I just wanted to say it :biggrin:.

    -Shark2k
     
  5. TEG

    TEG TMC Moderator

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    #5 TEG, Jan 18, 2009
    Last edited: Jan 18, 2009
    How to D/L YouTube HD MP4 to your system... While watching paste this to your browser:
    Oh wait, maybe I wasn't supposed to tell you that!:wink:
     
  6. TEG

    TEG TMC Moderator

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    To get started, search and read up on these terms:


    • Motion vectors
    • I-Frames
    • Mosquito Noise
    • Anti-Aliasing
    • Deinterlacing
     
  7. TEG

    TEG TMC Moderator

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    #7 TEG, Jan 18, 2009
    Last edited: Jan 18, 2009
  8. TEG

    TEG TMC Moderator

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    Hmm... Maybe I do need a faster computer :frown:
     
  9. shark2k

    shark2k Member

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    Know some of those, but will search and read up on the other ones.

    What are the specs of your computer?

    -Shark2k
     
  10. TEG

    TEG TMC Moderator

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    Lookup DCT (Discrete Cosine Transform) as well.
    The one I am using right now is a 3GHz P4, 1GB RAM, NVidia GeForce 7300GT, 1920x1200.
    It does fine for most things including HD MPEG2 playback.

    These clips appears to be AVC1/MPEG4. If I want to get completely smooth playback I probably need to get a newer video card with H.264/AVC hardware acceleration.
     
  11. shark2k

    shark2k Member

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    Will do.

    Isn't AVC1/MPEG4 supposed to be more efficient though? I guess in my mind I thought that would mean it wouldn't be as intensive on the CPU as MPEG2. Of course, my knowledge on this subject is not all that extensive so I could just be talking out my butt :biggrin:

    -Shark2k
     
  12. doug

    doug Administrator / Head Moderator

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    MPEG4 is more efficient in terms of image quality versus file size. But it takes more processing power to decode it than it does an MPEG2 of equivalent image quality. This was the point I was making above without getting too technical.
     
  13. TEG

    TEG TMC Moderator

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    Efficient as in more picture quality in less network bandwidth.
    But at the expense of more CPU cycles.

    I think the new YouTube HD is pushing the envelope a bit as to requirements for ISP connection and home computer power. A few year old or low end computer isn't going to cut it. Nor is a low grade internet connection.

    A full quality TV broadcast HD channel is like 19.2Mbit/sec.
    My internet download is < 1mbit/sec so to do streaming HD it needs to be a lot less datarate than what I get from watching an HD TV channel.

    That CNET clip is [email protected], so right there it is reduced from broadcast spec [email protected] Then the AVC1/MPEG4 can compress a lot more than the MPEG2 that is used by ATSC broadcast.

    That YouTube HD clip is 4:45 ( 285 seconds ) long, and the D/L file is 75,732,096 bytes so it is 265,726 bytes per second. Multiply by 8 and you get 2,125,813 bits per second. That is about 2x more data per second than my megabit link can download so waiting halfway through the D/L before starting playback would be in store. Then there is the playback issue. I made sure to get a system that could software decode ATSC HD video but that is MPEG2. These newer stream formats require more processing to decode so even when I download the clips they still stutter a bit on playback.

    (edit - I see Doug beat me to the response... I had to go check on dinner first)
     
  14. TEG

    TEG TMC Moderator

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  15. shark2k

    shark2k Member

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    Gotcha. Between your response and TEGs response I understand better now.

    I gotta say TEG, I feel for ya with that internet connection. I have FiOS and my download speed is 20 mbit/s (or 2.5 MB/s). My upload speed is actually faster than your download speed at 5 mbit/s :redface:

    I do have a nice desktop with a Intel Quad Core 2.66 GHz, 4 GBs Ram, XFX GeForce 8600 GT XXX graphics card and a 700 watt power supply. In my quest to try and be more energy efficient, I hardly use my desktop anymore (which is unfortunate since I just built it last year around April). Of course, I also use to keep my computer on 24/7 and I stopped doing that once I graduated college last year, of course since I stopped using it that didn't really matter :tongue: And since I got a laptop for X-Mas in 2007 I've been using that cause it is a good laptop, AMD Turion 64 x2, 4 GB Ram decent video card. I use it all the time and it is able to handle 720p HD video smoothly for the most part when I have it on max power. If I want 1080p I use my desktop.

    But thanks for the info guys. I thought I knew a decent amount about computers, but I know I can always learn and always realize I tend to over think things.

    -Shark2k
     
  16. Cobos

    Cobos S60 owner since 2013

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    Your P4 Ghz isn't as efficient per Mhz for decoding video as the newer Core 2 Duo either, so it looks like you are CPU limited. You might get rather far with a newest generation video card as they take a lot of the load off the CPU.

    Interesting that you've got about 1Mbit connection. I've got a pretty normal 9Mbit/1Mbit cable connection at home and at the high school where I work we've got a dedicated fiberoptic cable currently giving us 1Gbit both ways (propably because our Cisco Routers can't handly anything higher). Maybe we do have better Inet speeds here in Norway. :)

    [Actually looking at our bigger ISPs it seems the very lowest product I can find is 1000kb/s / 400kb/s and our speeds are a lot slower than Swedens.]

    Cobos
     
  17. dpeilow

    dpeilow Moderator

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    I think Sweden in particular and Scandinavia as a whole is currently a bit of an exception when it comes to really fast domestic connections, the rest of Europe and North America is still catching up.

    TEG is right that good quality HD is close to 20Mbit/s, but many broadcasters are using 8 or even 6 Mbit/s and getting acceptable results. I'd imagine Youtube is even less than that.
     
  18. Cobos

    Cobos S60 owner since 2013

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    You might be right in that, there's been a marked emphasis on getting "normal" stuff on the internet too. I do my taxes on through the states internet system. I only hand in a digital copy and I even do complicated taxes as I run a small "company". Most banks are closing down their branches as most banking is done through e-banks etc. Even our papers are doing pretty good as they've got very well visited webpages.

    Yes I think you are right. We will be getting in our apartment complex a direct fiberoptic link to our "cable" provider, offering VOIP, 10Mbit/10Mbit Internet and 15+ channels. Though the final stretch is done through Coaxial cable. You can upgrade internet to 100/10Mbit but then they say I should expect about 5-10Mbit to not be available when I'm watching TV as well. They do offer HD channels so you're estimate of 8-6 Mbit sounds about right.

    Cobos
     
  19. vfx

    vfx Well-Known Member

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    My head reels. The only connection I have is a wireless card in this tiny 11" dia. screen laptop.

    I just did a Speed Test check and am at 331 Download and 857 kbps Upload speeds. I'm grateful that's it's better than dialup.

    Needless to say, the choice to watch any video is well considered.
     
  20. TEG

    TEG TMC Moderator

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    YouTube Dwarfs Top Video Sites - US Ranks 15th in Broadband Speed Worldwide - US Broadband Penetration Creeps to 90.8% among Active Internet Users - August 2008 Bandwidth Report
    Even that 2.3mbps seems a bit high because it takes into account a lot of cable modem users which have typically 2x or 3x DSL download speed, but they have shared neighborhood links, higher connection latency, rate shaping, and very slow uploads, so in some ways DSL is more responsive.
    ( But in the case of Youtube HD downloads they seemed to have targeted that group and decided to let many DSL users get overloaded ).





    Adobe Forums - Help Me With This YouTube Test!!!
    Bigger and Better: Encoding for YouTube 720p HD - Web Video Techniques

    When I first played this video it stopped and started about every 5 seconds until I paused it for a while to build up a buffer:

    When you start playing it see how fast the faint red line jumps ahead of the playback location pointer. I bet you fast broadband users have the play-ahead-buffer red line jump to the end fairly quickly.
     

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