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  1. Member
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    Feb 2004
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    Just wondering about Digital Tv broadcasts. If they are broadcast in MPEG2 format (or am I wrong?) what happens with a live broadcast?

    Is it recorded in some high quality format and compressed on the fly via hardware and then transmitted?

    Just wondering how it works.
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  2. Member lumis's Avatar
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    Yeah, that's pretty much how it works.

    You'll notice a slight delay between analog & digital OTA broadcasts, it's not very significant though.

    You'll notice more of a delay between OTA & satellite tv.
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  3. Member edDV's Avatar
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    Mar 2004
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    A broadcast video server can use anything from uncompressed 4:2:2 component to encoded MPeg2. Encoding is usually done in hardware on the fly.

    A typical video tape machine (say SD Digital Betacam) records 10bit 720x480/576 2:1 compressed 4:2:2 and can play out analog or uncompressed serial digital interface (SDI). Some models can internally upscale to 1080i or 720p and output HD SDI. HBO plays many of their "HD" shows and movies this way. True HD formats include IMX-HD (variable bitrate), DVCProHD (100Mb/s) and HDCAM (144Mb/s).

    TV stations get their network feeds as mutiplexed MPeg2_TS usually at 45Mb/s. The TV station DTV playout server usually handles the MPeg2 streams without decompression but the air feed is reprocessed down to 14-19 Mb/s for HD and 3-5Mb/s for SD.
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  4. Member
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    Thanks for the replies.

    Are Mb/s mega bytes or mega bits pers sec? When people type that is there a way to tell the difference? I sometimes think MB= Mega byte and Mb = Mega bit but im just guessing.
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  5. Member edDV's Avatar
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    Mar 2004
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    Originally Posted by Rudyard
    Thanks for the replies.

    Are Mb/s mega bytes or mega bits pers sec? When people type that is there a way to tell the difference? I sometimes think MB= Mega byte and Mb = Mega bit but im just guessing.

    bits

    MB = Megabyte
    Mb = Megabit
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  6. Member
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    Apr 2004
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    Fairfax County, VA, USA
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    yeah, i live really near channel 7 in rossyln, VA (WJLA, ABC affiliate for Wash DC). anyways, they are actually based inside a shopping mall and they have their digital encoding servers facing the shop window, so i can tell you from firsthand observation that they feed the video into the server farm to encode and broadcast. it's so cool to watch all their networked Pentium 4s cranking out realtime MPEG 2...their hard drive lights are NEVER off.
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