[opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 29 Mar 2005 21:27:13 -0500
No. E-VSB works on the assumption that you can decode 8-VSB to begin with.
If you can never lock onto the 8-VSB carrier, you can't get at the enhanced
(the E part of E-VSB) forward error correction data.
E-VSB was designed to lower the C/N threshold, and thereby indirectly
increasing the echo tolerance for a given signal strength. But I doubt that
E-VSB is good enough for anything other than stationary use by a portable TV
in the kitchen. It certainly cannot be used in a mobile situation, as DVB
can.
From the July 2004 ATSC press release announcing the adoption of E-VSB:
"E-VSB provides optional modes of operation that allow broadcasters to
trade-off data rate for a lower carrier-to-noise threshold for some
services. Examples of potential applications for E-VSB include delivery of
"fall back" audio, programming services targeted at small DTV receivers with
indoor antennas, non-real time transmissions of file-based information to
handheld and pedestrian receivers, and robust data broadcasting to devices
such as desktop and laptop computers. "
John Shutt
----- Original Message -----
From: "Tom Barry" <trbarry@xxxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, March 29, 2005 9:20 PM
Subject: [opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
> Have there ever been any indications that E-VSB will be used by anyone
> at all for any purpose?
>
> - Tom
>
>
> John Shutt wrote:
>
>> Bert,
>>
>> The correct terms are 1/2 rate and 1/4 rate, not 1/2 additional FEC.
>> http://www.atsc.org/standards/a_53c_amend-1_corr-1.pdf
>>
>> As you correctly state, at 1/2 rate, for 542 Kbps, you get 18.1 Mbps in
>> the
>> main stream. You removed 1.3 Mbps from the main stream to get 542 Kbps
>> in
>> the robust stream. lose 2 bits to gain 1 bit.
>>
>> For 1/4 rate it's even worse. To achieve 542 Kbps robust, you get 16.9
>> Mbps
>> main stream. You removed 2.5 Mbps from the main stream to get 542 Kbps
>> for
>> the robust stream. You lose 4.5 bits to gain 1 bit.
>>
>> As I understand it, with DVB-H, as implemented within a 6 MHz DVB-T
>> stream
>> (as opposed to a
>> dedicated 5 MHz DVB-H carrier as Crown Castle is planning in the US), the
>> DVB-H data is time sliced within the DVB-T bitesream, and is a straight
>> one-for-one bit usage. The DVB-H data includes additional FEC, so for
>> your
>> 542 Kbps you may need to use 25% more bitrate for the additional FEC
>> data.
>> So you lose 677 Kbps from the main stream for a single DVB-H payload of
>> 542
>> Kbps.
>>
>> http://webapp.etsi.org/exchangefolder/en_302304v010101p.pdf
>> http://www.dvb.org/documents/DVB-H_Outline.pdf
>>
>> And I hate to point this out, but E-VSB may not even work very well.
>> E-VSB
>> was designed to improve reception, but not to increase battery life of a
>> portable device. DVB-H is first and foremost a standard to save battery
>> power.
>>
>> John
>>
>> ----- Original Message -----
>> From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
>> To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
>> Sent: Tuesday, March 29, 2005 6:33 PM
>> Subject: [opendtv] Re: TI Exec: Open Standards Crucial for Mobile TV
>>
>>
>>>Here's the E-VSB side. Maybe you can enlighten us on the
>>>equivalent DVB-T/DVB-H tradeoff?
>>>
>>>I'm just picking two values of robust stream, and the
>>>wide stream is supposed to be as robust as it is when
>>>the entire band is wide stream.
>>>
>>>For 542 Kb/s robust stream using 1/2 additional FEC,
>>>wide stream (2/3 FEC) is 18.1 Mb/s
>>>
>>>For 542 Kb/s robust stream using 1/4 additional FEC,
>>>wide stream (2/3 FEC) is 16.9 Mb/s
>>
>>
>>
>>
>>
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>
>
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