FPS x interval between scenes

Discussion in 'Dash Cam Software / Development' started by sraposo, Apr 28, 2017.

  1. sraposo

    sraposo New Member

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    Exactly, but although it is something that easily comes to anyone´s mind, it has to be technically proved.

    The help you all, here and in other "forums" (fora), have given is priceless and made possible to me get at the present point. Although there are many questions to be asked yes, now I have a clearer understanding related to this wmv file. As more discoveries and/or conclusions are got, I´ll post them in case of being useful for you and others.

    Thanks a lot, for while!
     
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  2. jokiin

    jokiin Well-Known Member Manufacturer

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    good luck with it all
     
  3. sraposo

    sraposo New Member

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    That segment that "surprisingly" is missing will justify a bunch of questions to the video recorder maker in order to make clear that such phenomenum unlikely (impossibily) would has happen due involuntary reasons.



    This will be taken in consideration. For while, this and my hypothesis are only possibilities that will have to be checked, but it´s good that such perceptions have been occurred.



    It´s also a good approach, but it will be probably easier to get samples from the maker or the representative.



    It´s also possible, because if it will be proved that file was tampered, they will be charged of providing an intentionally adulterated material.
     
  4. sraposo

    sraposo New Member

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    I´ve just discovered that Vegas Pro interpolates (virtual) frames in order to comply to the FPS specified in the project. Vegas Pro is not the appropriate tool for this, so it made me get erroneous conclusions, but not all is lost.

    I´ve checked that wmv file with ASFBin 1.8 and discovered that file is indeed 4FPS, 4 encoded frames per second, 4 real frames per second, but softwares like MediaInfo report a "nominal frame rate" of 30FPS. What does it mean?
     
  5. jokiin

    jokiin Well-Known Member Manufacturer

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    it may create a file with header info that tells the player to handle it like a 30fps file so that it can playback at normal speed, really need to know more about what camera it is from
     
  6. sraposo

    sraposo New Member

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    Sorry, but I didn´t get why would be needed to tell the player to handle it like a 30FPS file if the file indeed is 4FPS and in the header is also specified such a frame rate (4FPS). With a specification in the header of 4FPS and existing 4 encoded frames per second, video is played with the normal speed.
    Please, tell me what you may have noticed.
     
  7. SawMaster

    SawMaster Well-Known Member

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    Just guessing here but it's probably done just to continue fooling the noobs into thinking that the cam is actually recording @30FPS instead of @4FPS when the viewer display shows those figures. Most cam users do not know the good from the bad and simply presume the specs in the ad's are true. Honestly I'm not too far from there myself but I'm learning. SD card fakes are done similar, with the embedded data looking like 64GB to the machine while the actual capacity us much lower, and only discovered when the real capacity is used up :eek:

    Do try to find out what cam this is as that will help the knowledgeable folks here help you- that's what the good folks like doing here at DCT :D

    Phil
     
  8. sraposo

    sraposo New Member

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    No doubt that 30FPS header info may be a trick to impress the noobs, and, if so, such information may not be considered an evidence that the wmv video was tampered or, in some way, not original.



    "Do try to find out what cam this is as that will help the knowledgeable folks here help you- that's what the good folks like doing here at DCT"

    > In a (next) future, this and other information are expected to be got, but now I all have is this wmv file and everything is possible to be extracted, even in a limited way, will have to. So, in that (next) future, a complimentary will be required to present wider and deeper considerations.
     
  9. sraposo

    sraposo New Member

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    Hi all.

    At this moment, I think that a video editor that showed only encoded frames (nothing like Vegas Pro :) ) and exhibited low level data related to each frame( index data, payload data, ASF format structure fields and others) might unveil something useful. To use a hex editor would demand a huge effort to interpret all those fields, so it could be useful to check only little portions of bytes in a very low level, if really needed.

    ASFBin and Windows Media ASF View do only part of these functions each one. So, does anyone know a software that presents internal data related to each frame?
     
  10. sraposo

    sraposo New Member

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    To whom it can concern:

    FFDSHOW is configurable video and audio decoder and can be set to show many data of frame and file during video playing. Of course, the player will have to be configured to use FFDSHOW as decoder.
    (thanks to user Jagabo on videohelp forum)
     
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  11. sraposo

    sraposo New Member

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    Sirs,

    After deeper checking and compiling information that was posted during this thread, that´s what is relevant:
    1- ASF format video file (wmv file) made by a 4-channel dash cam recorder. Unknown maker, model and settings
    2- frame rate: 4 FPS. That´s what happens when video is played
    3- nominal frame rate: 30FPS
    4- from frame 0 till 87 and from 172 on, 2 cams are updated at each frame, alternatively to the other 2 cams
    5- from frame 88 till 171, a pair of even-numbered/odd-numbered (e.g 88/89, 90/91,...) shows the same image, changing all four cam images at a time
    6- frame 149 is missing
    7- there´s a 16-second jump in time showed by timestamps on frames 171 and 172

    The mission is check authenticity of this file.

    The main fact that catch anyone´s attention is item 7, that strongly suggests a cut off, but that is allegedly due to a recording system failure, according the person who provided the video.

    It´s quite curious what happens in itens 5 and 6

    In a small degree, item 3 doesn´t seem to comply to the average frames per second that are seen during playing.
     
  12. SawMaster

    SawMaster Well-Known Member

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    Again I suggest that you obtain some sample recordings from that cam to verify it's 'normal' functioning which should also show 'skips' in those other recordings too if it indeed defective. Only this time I wouldn't specify why I wanted those and I'd document their refusal. That should be enough to have the recording disallowed as being likely tampered with since they wouldn't let you examine the situation further as if they had something to hide. The odds are extremely strong that they won't have an adequate rebuttal and this will plant the seed of thought regarding an intentional deception, thus aiding your case. Moreso if they have done nothing since then to repair the 'faulty' cam system (which they probably haven't), and that would show that they aren't exercising proper cars and oversight of their buses, cams, and drivers too.

    I find it hard to believe that nobody knew about the 'defective' camera system beforehand. Anybody who would go to the trouble and expense of using such a system would also likely be checking it's vids (and those of the other buses) at least randomly on a regular basis. I don't know Aussie law but we both know that a lot of a case is as much human psychology as it is the law, especially if a jury is involved. I know some US attorneys who could make people think that Mother Theresa was more Satan than Saint, and appear to believe it themselves as they do that. I've seen those guys destroy their opposition even when their client was clearly in the wrong legally. You've got a win in your pocket.

    I do appreciate you sharing what you've found regards the vid recordings as it will be helpful to someone else someday and it is interesting to know regardless. And I'm curious to know the cam system they used- a fact which should emerge in time- soc that we can be sure t tell people to avoid if they are not going to be reliable. I've considered such a system myself, but now I'm glad that I stayed with my known reliable dashcams ;)

    Phil
     
  13. sraposo

    sraposo New Member

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    Complimentary info:

    8- Field "Creation Time" in "File Properties Object": 2016-2-11 10:23:12.686 (five days after accident). This field, according Advanced Systems Format (ASF) Specification, Revision 01.20.03, edited by Microsoft Corporation (December 2004), "specifies the date and time of the initial creation of the file. The value is given as the number of 100-nanosecond intervals since January 1, 1601, according to Coordinated Universal Time (Greenwich Mean Time).(...)"

    It´s quite curious what happens in itens 5, 6 and 8.
     
  14. sraposo

    sraposo New Member

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    Hi, Phil.

    Your suggested approach is the same as mine but, it is still unknown info about recording system maker, model, settings and whatever can help to evaluate the file authenticity, including sample recordings. All of that and other info will be requested during lawsuit, but for while the wmv video is the only thing available.
    My role is a forensic expert on Computer Science matter for one of the parties. I have not the power of request information directly to the other party, as the judge´s forensic expert has.

    It´s hard, I´d say impossible, to believe that a video recording system would fail about 2 seconds before the crash and would be available again 16 seconds later. Those observations I enlisted on previous e-mail strongly suggest (for while, it´s a clue, a strong one) that video suffered an edition.

    I do believe the told story is not the truth. Time will provide the facts.
     

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