Using my mac pro as an HDTV; choppy video - WHY?

Discussion in 'Digital Video' started by fairnymph, Dec 11, 2007.

  1. fairnymph macrumors 6502

    fairnymph

    Joined:
    Mar 12, 2007
    Location:
    Chapel Hill, NC
    #1
    I'm using an HDTV USB tuner: http://www.pinnaclesys.com/PublicSi...ers/PCTV+Mac/Pinnacle+TV+for+Mac+HD+Stick.htm


    with the mac pro in my sig. I'm getting good quality HDTV, except it's intermittently choppy video & audio with HD shows, and HD shows only. SD tv is fine, but I got this tuner specifically for recording HD shows.

    It can't be lack of processing power or RAM, because come on, my computer is very well endowed in those respects.

    Could it be the EyeTV Lite software? If so, is there another program that you would recommend that I could use with this tuner?

    I'm using an antenna, and I only have Safari, iTunes, and iChat open.

    I appreciate any help!
     
  2. Terry78 macrumors newbie

    Joined:
    Dec 27, 2007
    #2
    Could be the original transmission, or a throughput issue

    Sounds like macroblocking in the original transmission signal.

    First, you need to find out whether its the TV transmission signal itself. Do you or a friend have a HDTV (without the Pinnacle or the Mac) that you can watch to see if the originating TV station has occasional problems? If its this, you can't do anything about it.

    Some other ideas:

    Second, find out what resolution your received channels transmit in. Although I use cable, for example, my CBS station transmits in 1080i, while ESPN is 720p, and Fox is 480p (I think). The higher the resolution, the more data that is being transmitted - sometimes a lot more. The Pinnacle may not have the data throughput capability to pass it without problems. That could be why sometimes the TV signal is perfect (e.g., 480) and sometimes has problems (e.g., 1080 resolution transmission signals).

    Third, all of the components in the signal reception path must have the same data throughput capability as described above. This includes the cables you used. Some older cables can't pass all the data fast enough for 1080 signals.
    TVs and video cards/monitors that are 720 resolution should do a decent job of downscaling a 1080 signal, but its a possibility that downscaling issues be the cause. Downscaling errors look different than macroblocking, usually not as pronounced. Macroblocking is large blockshaped blotches.

    Good luck on your research!
     
  3. Terry78 macrumors newbie

    Joined:
    Dec 27, 2007
    #3
    Could be the original transmission, or a device throughput issue

    Sounds like macroblocking in the original transmission signal. High def is much more likely to have this than SD due to the much higher data rate transmission.

    First, you need to find out whether its the TV transmission signal itself. Do you or a friend have a HDTV (without the Pinnacle or the Mac) that you can watch to see if the originating TV station has occasional problems? If its this, you can't do anything about it.

    Some other ideas:

    Second, find out what resolution your received channels transmit in. Although I use cable, for example, my CBS station transmits in 1080i, while ESPN is 720p, and Fox is 480p (I think). The higher the resolution, the more data that is being transmitted - sometimes a lot more. The Pinnacle may not have the data throughput capability to pass it without problems. That could be why sometimes the TV signal is perfect (e.g., 480) and sometimes has problems (e.g., 1080 resolution transmission signals).

    Third, all of the components in the signal reception path must have the same data throughput capability as described above. This includes the cables you used. Some older cables can't pass all the data fast enough for 1080 signals.
    TVs and video cards/monitors that are 720 resolution should do a decent job of downscaling a 1080 signal, but its a possibility that downscaling issues be the cause. Downscaling errors look different than macroblocking, usually not as pronounced. Macroblocking is large blockshaped blotches.

    Good luck on your research!
     
  4. dapetrun macrumors regular

    dapetrun

    Joined:
    Feb 18, 2006
    Location:
    Western Pennsylvania
    #4
    When recording HD content, you don't need your software set to "Progressive" scanning. Removing "Progressive" will prevent your MBP from dropping any video frames and should playback smoothly. Worked for me...:D
     

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