Talk:ATSC standards

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This article does not have any information on the chroma subsampling (4:2:0, 4:2:2?) used the various modes. SolarWind

Who had the dumb idea to move ATSC to Advanced Television Systems Committee? Nobody will look it up or link it under that term and the acronym is still unambiguous. The only thing it does are unnecessary redirects and cumbersome links, where one of the key features of wikis is easy linking. Christoph Päper 14:23, 12 Mar 2005 (UTC)

I disagree. Almost all abbreviations have a disambiguation page. For consistency, ATSC should also retain the full name as its key. By the way, is this correct English: "Broadcasters who use ATSC and must retain an analog signal have to broadcast on two separate channels, as the ATSC system requires use of an entire six megahertz channel."User:Treeos 14:52, 30 Dec 2005 (UTC)

Any news on the ATSC and a 1080p60 standard? Jack Zhang 01:32, 8 April 2006 (UTC)[reply]

Certainly no plans for it that I've ever heard of, and I imagine it would work quite poorly given the bandwidth constraints and the fact that only mpeg-2 video is allowed. Snacky 04:04, 14 November 2006 (UTC)[reply]

Can anyone provide a quote from any standard that limits the number of DTV programs per frequency to 6? While I haven't searched the standards, I believe there is no such limitation, and I gather this was written by the same well-meaning but deluded person who wrote the "1 program per MHz" misinfo. Snacky 06:20, 27 May 2006 (UTC)[reply]

My understanding was a limit of either four or six. But I don't have access, at the moment, to the publications in which I read this—and it was in 1998. President Lethe 15:12, 27 May 2006 (UTC)[reply]

It's definitely not four. Was this publication an ATSC standard? Snacky 16:10, 27 May 2006 (UTC)[reply]

"Six channels" is a pragmatic limit based on the resultant subjective quality. There is no constraint by ATSC beyond that imposed by ISO/IEC 13818-1 (Table 2-18), which uses a 4-bit field in stream_id to identify the video stream number. Thus, sixteen channels are possible. algocu 12:41, 20 September 2006 (UTC)

It seems like you're right, and thanks for answering. Also, thanks for your recent improvements to the article! All I have to add is that, to be really, really pedantic, the limit of 16 video streams does not limit you to only 16 virtual channels. You can re-use the same streams across virtual channels however you like. This is quite pointless, but I've actually seen it done with audio. Snacky 00:45, 21 September 2006 (UTC)[reply]

The stream_id specifies the type of encoding, i.e. MPEG-1 vs. MPEG-2. There is effectively no absolute limit on the number of streams in ATSC itself, you have 1048575 possible VCT channels. In MPEG, you can use a number of PAT and PMT sections to achieve the number of programs you want. So the only absolute limit is your 8191 PIDs in an MPEG transport stream. If you take away overhead PIDs and assume one audio stream per program and with a shared static image video stream, you can still fit over 8000 channels. So the real limit would appear to be the number of minimum bitrate audio streams you could fit into 6Mhz with QAM-256 or 8-VSB encoding.

Digital receivers are limited to only 1,024 minor channels per major channel. -Dawn McGatney 12.30.07. —Preceding unsigned comment added by 69.139.231.9 (talk) 00:07, 31 December 2007 (UTC)[reply]

Its not clear from the article whether an ATSC tuner can display a PAL signal. Can someone who knows this please update the article with this information. —The preceding unsigned comment was added by Gaashish (talk • contribs) .

Why would it? PAL's an analog standard. Snacky 04:06, 14 November 2006 (UTC)[reply]

Sorry, we're not all experts ;-) I'm certainly not an expert in this area. Therefore please clarify your answer: if I buy a LCD TV in the US, with ATSC/NTSC tuner, can I connect it to the cable in The Netherlands (PAL)? Sorry for my ignorance....

In theory an ATSC television can display any PAL compatible video (576i), but you'd probably have problems with reception. The NTSC analog half will display the black-n-white picture, but no color. And the ATSC digital half is not compatible with the European Digital Television standards. So there's really no point in trying it. - Theaveng 19:53, 26 September 2007 (UTC)[reply]

I don't see why ATSC is compared to digital-terrestrial standards such as DVB-T or ISDB-T at some points in the article instead of comparing ATSC to to the more general standards DVB and ISDB. --Abdull 14:53, 14 March 2007 (UTC)[reply]

Because ATSC is a terrestrial standard. - Theaveng 19:55, 26 September 2007 (UTC)[reply]

Seems like original research; also, practical amateur radio systems cannot implement this and aren't likely to for decades. N8EVV aka Marc W. Abel 04:49, 28 June 2007 (UTC)[reply]

Is a DT2 channel part of ATSC? If so, is there an article that says what it is? Jim.henderson 02:34, 17 July 2007 (UTC)[reply]

The article does not explain, and I think it should explain WHY, rather than just say "it doesn't work". - Theaveng 19:57, 26 September 2007 (UTC)[reply]

   :Because of the need for the digital receiver to sample the transmitted signal at a
    very precise time, the digital receiver cannot be in motion... motion would cause
    a slight change in the timing of the received signal due to the Doppler effect; this
    would make accurate sampling of 8-VBS modulation impossible. Enhanced 8-VBS or E8-VBS
    seeks to overcome this limitation of motion by broadcasting a more robust signal at a
    lower data rate. -Dawn McGatney, 12.30.07.  —Preceding unsigned comment added by 69.139.231.9 (talk) 07:22, 30 December 2007 (UTC)[reply] 

The article briefly touches on something interesting but doesn't explain it:

If ATSC were able to dynamically change its error correction modes, code rates, interleaver mode, and randomizer, the signal could be more robust even if the modulation itself did not change. It also lacks true hierarchical modulation, which allows the SDTV part of an HDTV signal to be received even in fringe areas where signal strength is low.

Is this implying that an SDTV stream is sent with every HDTV stream? What are the characteristics of such "SDTV" feeds? Are they just 7xx*480 4:3 rebroadcasts of the NTSC analog feed (or what would be the NTSC analog feed, if it were still being broadcast in 2009)? A number of TVs are being sold as ATSC SDTVs, are these using the SDTV stream or they just reformatting the digital signal, at whatever resolution it is, to fit a ~500 line NTSC screen? --Squiggleslash (talk) 14:31, 12 December 2007 (UTC)[reply]