Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion. Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules. |
19th May 2005, 04:55 | #21 | Link | |
Registered User
Join Date: Jan 2005
Posts: 15
|
Quote:
Also, to my horror and dismay, a RCA Scenium 16:9 hdtv I had a chance to work with produces nearly 80.. 80 pixels of horizontal overscan in 1080i, and a considerable amount of vertical overscan, likely in scale. Apparently, in our age of high-def some companies feel that standards compliance (which hd standard specifies) is a useless prospect. When operating in 480i and p modes it produced very little overscan, seemingly similiar to a normal television. I think it's best to try and consider the overscan during filming, so you can find a good result without too much (possibly) quality detrimental post work. |
|
13th April 2006, 11:27 | #22 | Link |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
I'm glad this thread reached a sensible conclusion, because the earlier suggestion that 720 is equivalent to 704 "plus overscan" is simply wrong.
704 is approximately the width of the analogue active picture ( http://lipas.uwasa.fi/~f76998/video/conversion/ gives more accurate values). As explained on that page, samples outside this range (up to 720) are used when sampling analogue video signals to make sure pixels aren't lost at the edge when the sync isn't quite right, and to avoid single pixel transitions from black to picture causing ringing. The extra pixels are outside the 16:9 and 4:3 active picture area. It seems to me there's no need to crop anything when going from DV to DVD, but there is good reason to crop down to 704 before resizing to a 1:1 PC resolution. Cheers, David. |
12th February 2008, 20:29 | #23 | Link | |
Registered User
Join Date: Jul 2003
Posts: 28
|
Quote:
I am using x264 and capuring with NTSC DV If I want to see videon computer screen or on TV hooked to computer, while I want to preserve all video without cropping. Can I just set "-sar 10:11" when encoding and that's it? I used 8:9 all the time before (720x480 => 640:480, 4:3). But 10:11 looks even better, but I don't know for sure, because a difference is in subjective range. So which SAR is better for case above, 8:9 or 10:11? Thank you |
|
14th February 2008, 12:50 | #24 | Link |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
With the caveat that I've never used NTSC DV or x264, the "correct" pixel aspect ratio of NTSC DV is 10:11. Your camera may vary.
The software needs to crop to 704x480, and convert that cropped image to 640x480. If you want to keep the full 720 width, at the correct pixel aspect ratio, then you need about 654 pixels (!) in the output. Cheers, David. Last edited by 2Bdecided; 14th February 2008 at 13:56. |
14th February 2008, 14:34 | #25 | Link |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
I have a radical suggestion.
Given that... 1. It's very complicated: http://lipas.uwasa.fi/~f76998/video/conversion/ 2. It's even more complicated than that, because Jukka Aho "conveniently" ignored the analogue half lines. If you base the calculations on the correct analogue picture dimensions, it's even worse! 3. The basic descriptor in the MPEG-2 standards give the display aspect ratio rather than pixel aspect ratio, so "officially" (and incorrectly) 720x576 and 720x480 really do equal 4:3 (or 16:9). 4. Industry standards simply state the pixel aspect ratios as 59/54 (4x3 PAL) and 10/11 (4x3 NTSC). The PAL one is within 0.04% of the correct values (4x3 PAL = 1150/1053 exactly) if you take account of the analogue half lines properly, but these are often ignored in the digital world. 5. Downconversions from 16:9 HD fill all the 720 width, even though it's not there in the original, so the aspect ratio is almost certainly being changed. 6. PC playback software follows the MPEG-2 flags, and displays 720x576, 704x576, 720x480 and 704x480 all at 4x3 (or 16x9), while DVD players connected to calibrated TVs will only display the middle 702x576 as 4x3 (or 16x9) - there are always 2 or 16 pixels outside of the active area. Given all of this, it could be argued that to minimise aspect ratio errors across the full range of standards and display devices, the absolute "best" that can be done is to encode at 704x576 or 704x480 only (never 720, which is unpredictable on PCs vs TVs), and to treat that as the full active area. If you do this, then the error for PAL is less than one video pixel WRT the correct aspect ratio (where 702x575 = 4x3 or 16x9). I haven't been through NTSC from first principles, since the "correct" vertical height of an NTSC image is not clear to me. However, the error, if you believe the industry standards, is exactly zero for 4x3, and less than one pixel for 16x9. Therefore: "PAL" 4x3 768x576 = 704x576 16x9 1024x576 = 704x576 "NTSC" 4x3 640x480 = 704x480 16x9 854x480 = 704x480 So there you have it. Stop worrying. Treat 704 as the full picture and you'll never be more than a pixel out. 2012 Edit: 704 pixels is not strictly valid for anamorphic 16x9 DVD and may cause problems on some old DVD players details here: http://forum.doom9.org/showthread.ph...76#post1549376 Cheers, David. Last edited by 2Bdecided; 6th January 2012 at 19:16. |
14th February 2008, 15:16 | #26 | Link | |
Registered User
Join Date: Jul 2003
Posts: 28
|
Quote:
One more question, what does it mean in procedural terms, "treat 704 as the full picture"? a) Crop to 704x480 and apply SAR(10:11) ? b) Downscale to 720x480 => 704x480 and apply SAR(10:11)? c) Based on "your camera may vary", I should tape a square and find right AR, by applying ruler on my display. So its sizes on computer screen are equal. Ensuring display has 1:1 pixel AR, of course. Thank you! Last edited by Vetal; 14th February 2008 at 18:00. |
|
15th February 2008, 00:09 | #28 | Link | |
Registered User
Join Date: Jul 2003
Posts: 28
|
Thank David.
From what I got we are talking about the same thing: Quote:
720/480 * 10/11 = x/480 Where x= 654.5. So if I compress 720x480 with AR set to 10:11 inside mp4 container. And player will rescale it in windowed mode at 100% to 654x480. Or to any other scale while preserving AR, I.e. to full screen. Because cropping (720=> 704) does not change SAR, it cuts off 8-pixel wide bands from sides. And after the player render the result, result would be the same, but with some information cropped from the sides, nothing more than that. I.e. it would crop 2*8*(10/11) = ~14 pixels. And it would give 640 pixels width (654 - 14). But those 2x8 pixels are not a noise, it is part of the image. Why should I crop them, that is my question. Thank you Last edited by Vetal; 15th February 2008 at 00:14. |
|
15th February 2008, 13:20 | #29 | Link |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
If the player works correctly, and you're scaling on playback, then there's no need to crop.
It's MPEG-2 that I've had issues with; if the source is mod16 and contains only the active 4x3, it removes some of these issues. You may not have these issues with mp4 - I don't know, sorry. Cheers, David. |
15th February 2008, 18:44 | #30 | Link | |
Banned
Join Date: Oct 2001
Location: https://t.me/pump_upp
Posts: 811
|
Quote:
Software dvd players (like PowerDVD) show 720x576, 720x480MPEG-2 pictures with wrong aspect ratio because they use it as active area. Don't trust them! But 704x576, 704x480 handling is ok. Not enough: A lot of new movies are encoded with this issue. (All Harry Potters use 720x576 = 16:9). And so only the software players show the right AR on PC. And look at the circle calibration tool on dvd Ratatouille, circle 720x576 PAL - same issue! |
|
18th February 2008, 15:44 | #31 | Link | |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
Quote:
Maybe that's why they include a calibration tool - so you can adjust your TV to match the mistake on the DVD! Cheers, David. |
|
22nd February 2008, 17:45 | #32 | Link |
Registered User
Join Date: Feb 2008
Posts: 17
|
Table of commonly correct and incorrect encoding. Incorrect encoding may be implied from wrong assumption about the shape of the active display area of the source.
Code:
Source IAR FAR PAR Comment ========= ===== ===== ===== =============== PAL 4/3 5/4 15/11 12/11 Correct * PAL 4/3 5/4 4/3 16/15 Incorrect PAL 4/3 11/9 4/3 12/11 Correct * PAL 16/9 5/4 20/11 16/11 Correct * PAL 16/9 5/4 16/9 64/45 Incorrect PAL 16/9 11/9 16/9 16/11 Correct * NTSC 4/3 3/2 15/11 10/11 Correct * NTSC 4/3 3/2 4/3 8/9 Incorrect NTSC 4/3 22/15 4/3 10/11 Correct * NTSC 16/9 3/2 20/11 40/33 Correct * NTSC 16/9 3/2 16/9 32/27 Incorrect NTSC 16/9 22/15 16/9 40/33 Correct * and approximately correct with respect to a possible interpretation [2] of (analogue) PAL / NTSC standards, ITU-R BT.601, and all digital standards based on them (D1, DV,...). PAR: pixel aspect ratio, aka sample aspect ratio. FAR: frame aspect ratio, aka display aspect ratio, aka picture aspect ratio. IAR: image aspect ratio, aka storage aspect ratio. For example, 720/480 = 3/2 and 704/480 = 22/15. Reference [1] ISO/IEC MPEG - ITU-T VCEG Joint Video Team (JVT): Draft ITU-T H.264 (2002E) and ISO/IEC 14496-10:2002(E), aka AVC standard. Table E-1. [2] Jukka Aho: A Quick Guide to Digital Video Resolution and Aspect Ratio Conversions. http://www.iki.fi/znark/video/conversion/ Last edited by facialz; 3rd March 2008 at 20:38. |
9th March 2008, 17:03 | #33 | Link |
Registered User
Join Date: Feb 2008
Posts: 17
|
Table of PAL PARs, sampled under 13.5 MHz
Code:
Width Height PAR Error Used by ========= ====== =========== ======= ============== 702 576 128/117 +0.174% Aho, MeGUI 690 566 1132/1035 +0.147% SMPTE RP-187 702+54/59 576 59/54 +0.043% Sony, Apple 702 575 1150/1053 0 MPEG-1, MPEG-2 704 576 12/11 -0.111% MPEG-1, ASP, AVC, Microsoft 720 576 16/15 -2.330% Avidemux 720? 576? 1.066 -2.391% Adobe Table of NTSC PARs, sampled under 13.5 MHz Code:
Width Height PAR Error Used by ========= ====== =========== ======= ============== 711 487 1948/2133 +0.391% MPEG-1 710.85 486 4320/4739 +0.206% Aho 711 486 72/79 +0.185% Aho, MeGUI 710.85 485 38800/42651 0 ? 704 480 10/11 -0.068% MPEG-1, ASP, AVC, Sony, Apple, Microsoft 711 483 644/711 -0.433% MPEG-2 708 480 160/177 -0.633% SMPTE RP-187 720 486 0.9 -1.067% Adobe 720 480 8/9 -2.289% Avidemux Width and Height are of the reference image, i.e. one defining the 4/3 FAR. Errors are relative to the PAR based on the 52µs/575 PAL and (52+59/90)µs/485 NTSC reference image, respectively. Last edited by facialz; 11th March 2008 at 14:49. |
20th December 2010, 02:26 | #35 | Link |
Anime addict
Join Date: Feb 2009
Location: Spain
Posts: 673
|
In this page http://en.wikipedia.org/wiki/ATSC_Standards say something diferente at facialz. O_o
|
20th December 2010, 15:14 | #36 | Link | |
Registered User
Join Date: Dec 2002
Location: UK
Posts: 1,673
|
Quote:
(The only PARs I can find on that page are for x.264/AVC, and for 4:3 it says 10/11, just like facialz's post from March 2008.) Cheers, David. |
|
|
|