VideoHelp Forum

Try DVDFab and copy Ultra HD Blu-rays and DVDs! Or rip iTunes movies and music! Download free trial !
+ Reply to Thread
Page 3 of 4
FirstFirst 1 2 3 4 LastLast
Results 61 to 90 of 96
Thread
  1. Member DB83's Avatar
    Join Date
    Jul 2007
    Location
    United Kingdom
    Search Comp PM
    Originally Posted by Sharc View Post
    Originally Posted by SF01 View Post
    Theoretically physically cropping 720 to 704 with 1 pixel of blanking at each side left would result in the smallest distortion, if interpreted as 4:3, or 16:9 from full 704 line.
    I would expect this to work. It is probably the safest way as it does not depend on any sequence extension signaling. DVD players can only playback at DAR 4:3 or 16:9, independent of any correct or wrong SAR. I have however never seen a commercial DVD which was authored as 704x576, although it's legal. All I have seen are padded to 720.

    In fact most basic dvd-authoring programs do not offer 704*576.


    Also, maybe I already stated this, that according to the 'What is' it is only supported for 4:3


    Might do some experimenting of my own later today.
    Quote Quote  
  2. Originally Posted by DB83 View Post
    Originally Posted by Sharc View Post
    Originally Posted by SF01 View Post
    Theoretically physically cropping 720 to 704 with 1 pixel of blanking at each side left would result in the smallest distortion, if interpreted as 4:3, or 16:9 from full 704 line.
    I would expect this to work. It is probably the safest way as it does not depend on any sequence extension signaling. DVD players can only playback at DAR 4:3 or 16:9, independent of any correct or wrong SAR. I have however never seen a commercial DVD which was authored as 704x576, although it's legal. All I have seen are padded to 720.

    In fact most basic dvd-authoring programs do not offer 704*576.


    Also, maybe I already stated this, that according to the 'What is' it is only supported for 4:3


    Might do some experimenting of my own later today.
    I have just tested your sample, I cropped it to 702, rendered as 704x576 and put it in AVS2DVD, the DVD files were 704x576 with 1 pixel padding at each side. That being said, Vegas physically won't render to 702x576, when I write 702 in render template settings, it jumps back to 704.

    I must admit though, this is the only situation where it's easier with NTSC, because the active image is exactly 704x480 and concidentally MPEG supports 704 as it is multiple of 16, other than that all my experience with this botched format has been nothing but bollocks.
    Quote Quote  
  3. Originally Posted by SF01 View Post
    Originally Posted by Sharc View Post
    Originally Posted by SF01 View Post
    Theoretically physically cropping 720 to 704 with 1 pixel of blanking at each side left would result in the smallest distortion, if interpreted as 4:3, or 16:9 from full 704 line.
    I would expect this to work. It is probably the safest way as it does not depend on any sequence extension signaling. DVD players can only playback at DAR 4:3 or 16:9, independent of any correct or wrong SAR. I have however never seen a commercial DVD which was authored as 704x576, although it's legal. All I have seen are padded to 720.
    Through analog output everything is as ITU intended.
    The problem is with digital playback at the receiving end.
    Exactly, padded with black to keep active image in 702.
    Yes, and it has probably been said already:
    By design of the old school (SCART) DVD players, the center 702 pixels of the DVD were horizontally stretched according ITU. So as long as the DVD footage followed the ITU recommendation for the SAR, the playback was undistorted.

    By design of the newer 'digital' players, the usually 720x576 frame of the PAL DVD is forced to be played as either 4:3 or 16:9, independent of whichever SAR the underlying footage has, be it with or without borders. The player does not care as it does not know. Unfortunately, there is no SAR signalling in DVD spec, AFAIK. Also, there is no requirement that the SAR has to be ITU compliant. It's left to the authoring house how they crop, resize and add borders to the footage such as the movie will appear undistorted when played back at 4:3 or 16:9 DAR.
    Hence legacy ITU conformant and padded-to-720 DVDs are 2.5% off the kilter when played with current HW players. Most people probably don't care.

    I don't think that playing with ReStream will generally solve the issue, but you may try. Good luck ....
    Quote Quote  
  4. The same applies to compisite, component and separate video outputs.

    There is no need for SAR in DVD specification, only the DAR is important, by design the receiving end should be programmed to properly deal with it to retain backwards compatibility with ITU specifications, as we know unfortunately manufacturers are lazy and they did not make sure this is implemented, so the TV and software are not cropping to 702 and stretching to 4:3, or 16:9, which, again, should be taking place. There is no requirement, but it's only logical to make SD video according to SD video standards.

    ITU is not legacy, new documents do not negate the older ones, ITU.470 is still in power for analog signal, as is 601 for SD and 709 for HD.
    Quote Quote  
  5. Well, this just means that anything else but ITU compliant SARs for DVD should never have been accepted. But that's definitely beyond our control.
    Quote Quote  
  6. Unfortunately, as tiem goes by new engineers know less and less about older technology, this is why mostly older people work at cassette tape production plants.

    Anyway, I am here to make ITU-compliant DVDs and I can achieve that by renderign materials in Vegas either as ready MPEG program stream, or as DV and then concert in AVS2DVD, because the first method does not always fit on DVD5. Though I wanetd to kill two birds with one stone and make ITU compliant DVD that would have sequence extension cropping information for proper playback through HDMI and on PC.
    Quote Quote  
  7. Yes, I understand the gordian not you are trying to solve. The issue might just be that the sequence extension is not part of the DVD standard, AFAIK. So most DVD players will probably just ignore it. Anyway, learning about your experience with the sequence extension is most appreciated.
    Quote Quote  
  8. I will experiment with the Restream and see it it makes any differance, the question is whether VLC can read it from MPEG file anyway, because it has the primitive aproach to SAR and will play 720x576 as regular 4"3 and 16:9 without the correction of he actual active image, I had to add custom aspect ratios to counter this, as if the creators cuoldn't have taken care of it, which reminds me to suggest it on their forums, as this problem was reported mutiple times.
    Quote Quote  
  9. The MEPG 2 sequence_display_extension is part of the DVD spec. But the only way I've seen it used is for widescreen video flagged as 4:3 DAR -- the sequence_display_extension indicates the 4:3 DAR is in a 540 pixel wide portion of the frame, making the full frame 16:9. Players use the 540x576/480 portion of the frame to output 4:3, the full 720x480/576 to output 16:9.
    Quote Quote  
  10. Member DB83's Avatar
    Join Date
    Jul 2007
    Location
    United Kingdom
    Search Comp PM
    For my own amusement - can upload the samples if required - I created two dvd folders with avstodvd. The first was 704*576 4:3 and the second 704*576 16:9.


    Now both required manipulation of the avisynth script since in both case they wanted to resize my externally encoded 704*576 samples to 720*576.


    In neither case did avstodvd acknowledge that the 704*576 sources were dvd-compliant and would re-encode regardless.


    Now I just used PC based playback, vlc and PowerDVD. VLC was 'interesting' since I typically have no issue with dvd playback but it totally distorted both samples neither being anything even close to 4:3 or 16:9. On the other hand, PowerDVD played both correctly with the 4:3 having the typical pillar-box bars and the 16:9 filling the monitor screen. Now I fully expected the 16:9 one to fail so was rather surprised by the result.


    My version of avstodvd is quite old so pre-dates when ffmpeg was introduced as an encoding engine. But it works for me so I rarely upgrade just for the sake of it.
    Quote Quote  
  11. Like I said, I used your sample you posted earlier, rendered it to 704x576 program stream in Vegas (128:117 pixel aspect ratio), places in AVS and it resulted in 704x576 VOB file in DVD folder structure. With the 4:3 flag in it it would be displayed as 768x576 in Vegas, technically sruare pixels would be 770x576, but I must admit, nobody will see that.
    For 16:9 video in 704x576 would result in ~1027x576, though I suppose the fractional pixels would be dropped, so it would be 1026x576, again two 1 pixel wide black columns at the sides, upscaled to 1920x1080 they would make maybe 2 pixel wide black bars that again noone would notice.
    And 704 samples in analog playback would still be converted to analog using the 13,5MHz standard, so it would give 52,(148) Ás, which incidentally is NTSC line length, either way it would have at both ends generated nominal analog blanking so still the 702 would be stretched on analog screen.

    But then again, I would have to weite custom aspect ratios for 704x576 videos in VLC.
    Quote Quote  
  12. Who cares about analog output from DVD players these days? Everyone uses the HDMI outputs and they all upscale the full frame to the flagged DAR.
    Quote Quote  
  13. Originally Posted by jagabo View Post
    Who cares about analog output from DVD players these days? Everyone uses the HDMI outputs and they all upscale the full frame to the flagged DAR.
    My country is a little bit far behind, people still use older DVD players with analog outputs, Blu-Ray didn't get significantly popular before the streaming cemented their position, so many people switched from DVD to streaming, while still having old players hooked up with analog connectors to TV, or i the case of the guy I made DVDs for to a projector in a music club, where I film concerts.

    And HDMI outputs do not upscale on the DVD level, it's the TV that upscales the input signal and can't properly expand non-quare pixels as per ITU specification. Unless there are obviously players that do upscale, but those would be the BD players, because how an SD DVD player wuold have a circuitry to upscale to HD, when the HD techology wasn't on the market.
    Quote Quote  
  14. Originally Posted by SF01 View Post
    Originally Posted by jagabo View Post
    Who cares about analog output from DVD players these days? Everyone uses the HDMI outputs and they all upscale the full frame to the flagged DAR.
    My country is a little bit far behind, people still use older DVD players with analog outputs, Blu-Ray didn't get significantly popular before the streaming cemented their position, so many people switched from DVD to streaming, while still having old players hooked up with analog connectors to TV, or i the case of the guy I made DVDs for to a projector in a music club, where I film concerts.
    Then all you have to do is encode ITU caps at the full ITU 720x576 frame and set the sequence_display_extension to 702 -- then hope your player(s) conform at the various outputs.

    Originally Posted by SF01 View Post
    And HDMI outputs do not upscale on the DVD level, it's the TV that upscales the input signal
    Upscaling players (most modern players) upscale before sending the video to the HDMI port. I've never tried using a sequence_display_extension to specify the area to be upscaled -- I don't know how many players will respond to it, and in what way.

    By the way, MPEG 2 encoders won't encode a 702x576 frame because mod 16 frame sizes are required.
    Quote Quote  
  15. Analog is always properly displayed, it's the digital that's prolematic.
    Modern yes.

    I know, this is why I was talking about 704 few posts back.
    Quote Quote  
  16. Originally Posted by SF01 View Post
    Analog is always properly displayed, it's the digital that's prolematic.
    Modern yes.
    No, that's backwards. The DVD/MPEG 2 specs are quite clear that the full frame encompasses the DARn (in the absence of a sequence_display_extension that indicate otherwise). It's the analog output of old DVD players that's wrong.
    Quote Quote  
  17. Originally Posted by jagabo View Post
    Originally Posted by SF01 View Post
    Analog is always properly displayed, it's the digital that's prolematic.
    Modern yes.
    No, that's backwards. The DVD/MPEG 2 specs are quite clear that the full frame encompasses the DAR. It's the analog output of old DVD players that's wrong.
    Backwards compatible.
    The DVD spec is REC.601 compliant and backwards compliant with REC.470. So that the analog output would be properly generated to be compliant with REC.470.
    Analog output is correct for both old and new players, the digital output of upscaling players, TV display and PC software do stuff technically wrong by not taking into account that the active image is 702, not full-widrth of 720 wide.
    It's the same with DV camcorders, but they actually use full 720 pixels for video, BUT they use REC.470 and 601 compliant pixel width.
    Quote Quote  
  18. Originally Posted by SF01 View Post
    The DVD spec is REC.601 compliant and backwards compliant with REC.470. So that the analog output would be properly generated to be compliant with REC.470.
    No, the DVD spec is not compatible with rec.601/470. Old players used off-the-shelf rec.601/470 DACs because they were available, cheap, and close enough.[/QUOTE]
    Quote Quote  
  19. Where is it switten in the DVD spec then?
    And why would DV video be REC.601 compliant and DVD not?
    Quote Quote  
  20. Originally Posted by SF01 View Post
    Where is it switten in the DVD spec then?
    I don't have the DVD spec -- it's very expensive you need to sign an NDA to get it. But someone here claimed to have the spec and he said the only thing it said about aspect ratios was that only two were supported: 4:3 and 16:9 DAR. And it referred you to the MPEG 2 spec for further details. You can find the MPEG 2 spec online. It clearly states the entire frame constitutes the DAR:

    Image
    [Attachment 54659 - Click to enlarge]


    Originally Posted by SF01 View Post
    And why would DV video be REC.601 compliant and DVD not?
    Because DV is not DVD. Each has their own spec.
    Quote Quote  
  21. A further reading would be interesring.
    But then again, why would the deliberately make DVD spec non-compliant with REC.470 and 601, when it supports 704x480 adnd 704x576 resolutions and consiedring the fact that it was taken into account that people would burn their DV tapes on DVDs and DV is strictly ITU-compliant. Especially considering that "entire frame" is reconstructed by taking the 720 samples and using 13,5MHz sample rate to convert it to analog signal, which is 53,333 microseconds, while the "active region of the display" shows only 52 microseconds, because you know the analog displays work in compliance with REC.470.

    The same with analog to digital converters converting analog signal that is REC.470 compliant to 720x576 video that is REC.601 compliant, which results in active image area of 702 pixels. So that would make DVD a flawed product, because it would display REC.470 and 601 images incorrectly and somehow it doesn't, maybe because it is REC.601 compliant.
    Quote Quote  
  22. Originally Posted by jagabo View Post
    Originally Posted by SF01 View Post
    Where is it switten in the DVD spec then?
    I don't have the DVD spec -- it's very expensive you need to sign an NDA to get it. But someone here claimed to have the spec and he said the only thing it said about aspect ratios was that only two were supported: 4:3 and 16:9 DAR.
    We can collect some details from here, which is however not the official DVD spec. The 3 Aspect Ratios (DAR) are 1:1, 4:3 and 16:9, and the sequence_display_extension is also mentioned. We would have to assume that this mpeg-2 part is included in the DVD spec although it is not explicitly said so. The DVD spec includes only a subset of the mpeg-2 spec.
    http://dvd.sourceforge.net/dvdinfo/mpeghdrs.html
    Quote Quote  
  23. Member Cornucopia's Avatar
    Join Date
    Oct 2001
    Location
    Deep in the Heart of Texas
    Search PM
    Image
    [Attachment 54661 - Click to enlarge]
    Image
    [Attachment 54662 - Click to enlarge]


    You really don't necessarily need to agonize over such a small difference (2.5%). Hollywood doesn't.

    See the circles above. That's the difference between the 2 aspect ratios. Can you visibly spot which one is not a perfect circle? (WITHOUT resorting to graphing or magnifying or using a test app)


    Scott
    Quote Quote  
  24. Yes, A is perfect.
    If I can see it, others can see it too, I'm going through old DVDs and they have digital blanking and adhere to ITU standards.
    Tell the people who agonize that 24fps films are sped up for PAL instead of applying Euro pulldown not to agonize over it.

    The standards are here to be adhered to to have all the products play with the same properties.
    Quote Quote  
  25. Well, what's the difference between agonizing about slight geometric distortions or slight audio pitch shifts? Who cares?
    It's justifiied just to understand what's happening, I think.
    Interestingly, the topic and confusion is brought up again at again since the introduction of DVDs.
    Quote Quote  
  26. Visual distortion is visible, higher pitch is never niticable, when you don't have a referance. Imagine your cassette deck always played tapes faster, you'd never know, until one day you hear the song on the radio, but when you see distorted image you know immidiately.

    Yes, I've tracked down threads going as far back as 2002. I've seen countless threads where people have no idea how to convert SD material to and from...
    Quote Quote  
  27. Originally Posted by SF01 View Post
    Visual distortion is visible, higher pitch is never niticable, when you don't have a referance.
    I would have to disagree. Some people have the pitch perfect. They easily notice when a piano is slightly off. They can tune an instrument without any tools or auxiliary frequency references. Whether they agonize over it, I don't know. They probably just notice.
    Quote Quote  
  28. Perfect pitch does happen, but then again, the speedup is almost exactly a semitone.
    They still have to have a stanadrd referance for example 440Hz, there were different stanadrds throughout the years and different tuning systems, if they know what to notice in the first place.
    Quote Quote  
  29. Originally Posted by SF01 View Post
    A further reading would be interesring.
    But then again, why would the deliberately make DVD spec non-compliant with REC.470 and 601, when it supports 704x480 adnd 704x576 resolutions and consiedring the fact that it was taken into account that people would burn their DV tapes on DVDs and DV is strictly ITU-compliant. Especially considering that "entire frame" is reconstructed by taking the 720 samples and using 13,5MHz sample rate to convert it to analog signal, which is 53,333 microseconds, while the "active region of the display" shows only 52 microseconds, because you know the analog displays work in compliance with REC.470.

    The same with analog to digital converters converting analog signal that is REC.470 compliant to 720x576 video that is REC.601 compliant, which results in active image area of 702 pixels. So that would make DVD a flawed product, because it would display REC.470 and 601 images incorrectly and somehow it doesn't, maybe because it is REC.601 compliant.
    Apparently the ITU bodies confused themselves. The EBU tried to clarify
    Image Attached Thumbnails r092.pdf  

    Quote Quote  
  30. A very nice document, the 53,333 microseconds of line to be sampled to 720 was chosen probably so that it could accomodate both PAL and non-PAL systems, where the active image of of different line-length, but the troubles it caused are problematic to this day, hence this thread...

    Code:
    In 625-line television systems sampled to ITU-R Rec. BT.601 part A, only the central 702 luminancesamples of the digital active line (samples 9-710 inclusive) and their associated chrominance samplesshould be used to carry the active picture. The remaining 18 luminance samples and their associatedchrominance  samples  may  be  used  to  carry  picture  information  only  but  for  no  other  purpose.    Itcannot be guaranteed that picture information in these samples will be displayed in either 4:3 or 16:9aspect ratio images.
    Which is why DV video uses all 720 samples, while the ITU compliant image has the image at least in the center 702 samples.
    Quote Quote  



Similar Threads