ATSC (HDTV) basics discussion thread

[Doom9]

Here you go: http://forum.doom9.org/showthread.php?s=&threadid=76006

As for the DVB basics, I'd like some feedback. Omissions, errors, major blunders, etc.. just let me know (I know it's not a work of scientific quality). I've read about different modulation mechanisms used for HDTV, but curiously, the specs really only mention what I put in the basics. I plan to go into A/65b, A/69 at a later point. Now I guess we need somebody to start a hardware / software list and somebody to turn the instructions posted for capturing into a full blown guide.

[Xesdeeni]

It looks like you are mixing your metaphors on the frame rates. You say that 1920x1080 can be 29.97/30 fps interlaced, but you say 704x480 and 640x480 support 59.94/60 fps interlaced.

What does a DAR of 1:1 mean for 1920x1080, 1280x720, and 640x480? A square screen?

I was under the impression that the satellite standard allowed 16:9 similar to DVD's "anamorphic" mode.

Xesdeeni

[Doom9]

You say that 1920x1080 can be 29.97/30 fps interlaced, but you say 704x480 and 640x480 support 59.94/60 fps interlaced.I don't follow.. I don't have the PDFs on my right now, so maybe I mistook that info but it sounds plausible to me. Just because DVD doesn't support framerates higher than 29.97 doesn't mean HDTV should not. And the largest HDTV resolution is usually limited because it is otherwise already hard to process (1080p for instance is not part of any standard.. but it's defined as an option in the Japanese HDTV specs).

A 1:1 DAR means the picture isn't stretched for playback at all and that's all there really is to it. If it makes sense to use such a DAR is another question altogether ;)

I'd assume that the DAR specifies a stretching ratio but you've effectively given me something to think about as 1920x1080 is already 1:1.77 = 16/9. I'll get back to you on that.

[Xesdeeni]

Originally posted by Doom9
I don't follow..For NTSC and interlaced ATSC modes, there are 59.94/60 fields per second. I've seen this written as "29.97/30 fps interlaced" and as "59.94/60 fps interlaced." I don't know which is correct (I tend to sit on the fence and use 'f' for field and 'F' for frames, so I'd say "29.97/30 interlaced Fps" or "59.94/60 interlace fps"). But in your write-up, you use both. However, if you use "29.97/30 fps interlaced" (like you did for 1920x1080i), then when you say "59.94/60 fps interlaced" (like you did for 704x480 and 640x480), you are actually talking about 119.88/120 fields per second. This would be the equivalent (in bandwidth) of 59.94/60 progressive fps, a.k.a. the ellusive 1080p. I'm pretty sure there isn't such a mode ;).

Xesdeeni

[Doom9]

ahem.. I'm afraid you're mistaken there. A/53, Table A3 is quite clear that these are frame codes. 29.97fps interlaced means 59.94 fields of course, but 59.94 frames per second is also allowed for certain resolutions. Also, I rechecked the 1920x1080 resolution and it's allowed in progressive mode at frame rates of up to 30 fps progressive and interlaced (so the latter would be 60 fields per second).

I use fps for the refresh rate, so 30fps interlaced means 60 fields per second, and 30 fps progressive means 30 frames per second. I think this is pretty standard.. hardly anybody says interlaced PAL is 50 fps.. it's still 25 fps but it's interlaced.

Check page 29 of the following specs document: http://www.atsc.org/standards/a_53b_with_amendment_1-2.pdf

However, I'm effectively at a loss to explain the 16:9 DAR flag for high def content as those formats are already in 16:9 format and no stretching would be needed for playback.. but.. could it be that there are screens with a resolution higher than 1920x1080 so that the 16:9 flag would lead to stretching of such content? Alternatively, if the flag were to be used, the video would have to be stretched, then downscaled to screen resolution which doesn't make much sense to me.

[Xesdeeni]

Originally posted by Doom9
ahem.. I'm afraid you're mistaken there. A/53, Table A3 is quite clear that these are frame codes. 29.97fps interlaced means 59.94 fields of course, but 59.94 frames per second is also allowed for certain resolutions.No question. But, those are 59.94/50 progressive fps. However, you said...1920x1080 at 23.976/24/29.97/30 fps progressive, and 29.97/30 fps interlaced....and then...704x480 at the same framerates as 1280x720, but in addition to that, 59.94 and 60 fps are also supported in interlaced mode. Both 4:3 and 16:9 DAR is supported 640x480 supporting all previously mentioned framerates in progressive mode, and 59.94/60 fps in interlaced mode, at both 1:1 and 4:3 DARSo if the first is right, the second isn't.Also, I rechecked the 1920x1080 resolution and it's allowed in progressive mode at frame rates of up to 30 fps progressive and interlaced (so the latter would be 60 fields per second).A-HA! Compare this to the above quote :)I use fps for the refresh rate, so 30fps interlaced means 60 fields per second, and 30 fps progressive means 30 frames per second.Which is what I thought you meant, but by that logic, the above quoted piece ("59.94/60 fps in interlaced mode") would mean 704x480 and 640x480 had modes that output 119.88/120 fields per second.Check page 29 of the following specs document: http://www.atsc.org/standards/a_53b_with_amendment_1-2.pdfYes, and I don't see 59.94/60 fps interlaced. That is, I don't see 7 and 8 under the frame rate column on the same line as 0 in the progressive sequence column.However, I'm effectively at a loss to explain the 16:9 DAR flag for high def content as those formats are already in 16:9 format and no stretching would be needed for playback.. but.. could it be that there are screens with a resolution higher than 1920x1080 so that the 16:9 flag would lead to stretching of such content? Alternatively, if the flag were to be used, the video would have to be stretched, then downscaled to screen resolution which doesn't make much sense to me. Yes, it seems redundant. To display 1920x1080 on a 16:9 screen, you would display the pixels as squares. And to display the pixels as squares, you'd have a 16:9 display. The same is true for 1280x720 and 640x480 (except for 4:3). I don't get that, either.

Xesdeeni

[eb]

sorry may be my post can be helpful,

at present EURO180i is providing transmission with frame size 1920x816 so some flag is needed to stratch this to 16:9

eb

[Doom9]

@Xesdeeni: long talk for a simple correction.. if you just quoted just the part that was wrong, it would've gone much quicker ;) I admit, 704x480 doesn't support 59.94/60 fps interlaced.. it only does 29.97/30 fps in interlaced mode.

@eb: you're in the wrong thread... this is about ATSC, what you mean is DVB ;)

[eb]

Qoute from http://www.coolstf.com/


What is ATSC?
ATSC is Advanced Television Systems Committee which is destined to replace NTSC as the method of terrestrial television transmissions in the United States, Canada, Mexico, South Korea and Taiwan. Like DCII, ACTS uses the MPEG-2 video specification, but bastardizes everything else, making North American (and South Korea/Taiwan) an island in a world of standards.
ATSC is almost exactly the same as Digcipher 2 and of course it's no surprise that General Instrument was on the comitee that recommended ATSC to the FCC. In theory, ATSC and Digicipher 2 have a couple of advantages over MPEG-2/DVB, especially in the area of signal aquisition time, however, this is not enough to justifying a totally different standard than the rest of the world.
An interesting tidbit about why ATSC uses AC3 for audio and not Musicam recently surfaced. In the field trials during the development of the ATSC specification, both AC3 and Musicam were tested. Technically both have the same merits, including the ability to do 5.1 audio in the same bandwidth. However, AC3 was chosen because in one area, it was tested to have better performance than Musicam. It was later discovered that the testing procedure was flawed and that subsequent re-testing after the standard was published showed that AC3 and Musicam performed equally as well.
Like DVB/MPEG-2, ATSC supports HDTV.


What is DVB?
DVB stands for Digital Video Broadcast and is a standard based upon MPEG-2 video and audio. DVB covers how MPEG-2 signals are transmitted via satellite, cable and terrestrial broadcast channels along with how such items as system information and the program guide are transmitted along with the scrambling system used to protect the signal.
With the exception of the United States of America, Mexico, Canada, South Korea and Taiwan, DVB has been adopted by just about every country in the world for digital TV & radio. This document concentrates on DVB-S, the satellite format of DVB - DVB-C is the specification for DVB/MPEG-2 over cable and DVB-T is DVB/MPEG-2 over terrestrial transmitters.
END of QUOTE

On http://forum.doom9.org/showthread.php?s=&threadid=75909 there is NA site address from that I downloaded sample of HDTV and it was 1920x816 /check this sample best in DVD2AVIT3/
sorry again for misleading the thread

eb

PS
@ Doom9,
If needed please remove this post