Uncle Penn
I was listening to a popular radio consumer advocate. He said that you will actually get a better picture using an antenna to get your HDTV vs. cable or satellite. The reason given was that cable and satellite have to compress the signal, but free over-the-air does not.
In the computer world, there's lossy compression, like JPEG, where some clarity is lost. Then there's ZIP where no data is lost and you receive a perfect reproduction.
So I guess their are 3 questions:
1. Is an over-the-air signal compressed or not?
2. Do cable and sattellite companies use a "lossy" compression scheme for the HDTV signals.
3. Is it true that the HDTV picture is superior if received from over-the-air transmission.
To Pancakes - HDTV has resolutions of 1080i and 720p, both superior to progressive DVD which is 480p.
Answer
The ATSC standard for HDTV transmission is MPEG-2 compression and 19mbit data rate. OTA and cable both use MPEG-2, as does most satellite transmission. Some recent satellite local stations are compressed with MPEG-4. All HDTV is compressed. However, the MPEG specs allow for different amounts of compression and different qualities. When OTA utilizes the full bandwidth for a single HDTV channel at 19mbs, you will get the best quality obtainable from HDTV. However, many OTA stations will broadcast several programs on sub-channels simultaneously with their HD channel. That steals bandwidth and bitrate from their HD channel, and if that is done too much, the HD picture quality will suffer (the subchannels are usually not HD). So you cannot lump all OTA into one category for picture quality.
The same is true for cable channels; they have the option of retransmitting the exact signal broadcast, in which case the cable will have the same quality as the broadcast. However, some cable systems will decompress and recompress the signal so they can use a lower bitrate and less bandwidth. If they do that, the cable's picture will be poorer than OTA. It is also possible for the cable to receive a higher-quality signal from the station (less strongly compressed) that the networks use to distribute their HD content. If the cable system then compresses that signal to a high bitrate, but the broadcaster limits its bandwidth, the cable signal would be better. i do not know if this latter approach is being used by any cable companies at this time, but it is a possibility.
Finally, satellite compression is often more severe than OTA or cable, and my experience with satellite HD is that for the major networks, it is not as good as OTA or cable. However, special HD channels on satellite (HDnet, Discovery HD) are excellent.
In summary, the answer to our question is: it depends.
Finally, all MPEG compression schemes are "lossy". It would be impossible to get the HD picture in the allotted bandwidth with lossless compression. But the degree of "loss" is flexible and up to the party doing the enccoding.
The ATSC standard for HDTV transmission is MPEG-2 compression and 19mbit data rate. OTA and cable both use MPEG-2, as does most satellite transmission. Some recent satellite local stations are compressed with MPEG-4. All HDTV is compressed. However, the MPEG specs allow for different amounts of compression and different qualities. When OTA utilizes the full bandwidth for a single HDTV channel at 19mbs, you will get the best quality obtainable from HDTV. However, many OTA stations will broadcast several programs on sub-channels simultaneously with their HD channel. That steals bandwidth and bitrate from their HD channel, and if that is done too much, the HD picture quality will suffer (the subchannels are usually not HD). So you cannot lump all OTA into one category for picture quality.
The same is true for cable channels; they have the option of retransmitting the exact signal broadcast, in which case the cable will have the same quality as the broadcast. However, some cable systems will decompress and recompress the signal so they can use a lower bitrate and less bandwidth. If they do that, the cable's picture will be poorer than OTA. It is also possible for the cable to receive a higher-quality signal from the station (less strongly compressed) that the networks use to distribute their HD content. If the cable system then compresses that signal to a high bitrate, but the broadcaster limits its bandwidth, the cable signal would be better. i do not know if this latter approach is being used by any cable companies at this time, but it is a possibility.
Finally, satellite compression is often more severe than OTA or cable, and my experience with satellite HD is that for the major networks, it is not as good as OTA or cable. However, special HD channels on satellite (HDnet, Discovery HD) are excellent.
In summary, the answer to our question is: it depends.
Finally, all MPEG compression schemes are "lossy". It would be impossible to get the HD picture in the allotted bandwidth with lossless compression. But the degree of "loss" is flexible and up to the party doing the enccoding.
Analog cable on HDTV?
TP
-Would analog cable appear horrible on a HDTV?
-If yes, would I have to change HDTV to SD mode every time I watch analog cable?
-Does every HDTV have a SD mode?
Answer
Every HDTV will receive analog signals, and if you plug in your analog cable into the antenna input of your TV that what you will get (you still must scan for channels in the setup process). The picture quality depends on how good your cable system is. If the provide a nice clean signal they won't look too bad, but any defects will show more on the high def screen.
If you get digital cable, you connect the cable box using an HDMI cable and you will get whatever is provided by the cable signal (SD, HD).
On any digital set, anything the signal carries is what you will see, HD or SD--you don't have to switch anything.
Every HDTV will receive analog signals, and if you plug in your analog cable into the antenna input of your TV that what you will get (you still must scan for channels in the setup process). The picture quality depends on how good your cable system is. If the provide a nice clean signal they won't look too bad, but any defects will show more on the high def screen.
If you get digital cable, you connect the cable box using an HDMI cable and you will get whatever is provided by the cable signal (SD, HD).
On any digital set, anything the signal carries is what you will see, HD or SD--you don't have to switch anything.
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