Talk:Digital video

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Film (Rated Start-class)
WikiProject icon This article is within the scope of WikiProject Film. If you would like to participate, please visit the project page, where you can join the project and see lists of open tasks and regional and topical task forces. To use this banner, please refer to the documentation. To improve this article, please refer to the guidelines.
Start-Class article Start  This article has been rated as Start-Class on the project's quality scale.
Checklist icon
Taskforce icon
This article is supported by the Filmmaking task force.
 
WikiProject Media (Rated Start-class)
WikiProject icon This article is within the scope of WikiProject Media, a collaborative effort to improve the coverage of Media on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Start-Class article Start  This article has been rated as Start-Class on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.
 



I came to Wikipedia to look up some of the terminology in article Digital Video & HDTV.

Digitized Video Standards NTSC PAL SMPTE 259M CCIR 656 EU95 SMPTE 292M

Serial Digital Video Formats SMPTE 259M ITU-R601 CCIR 656 EU95 SMPTE 292M

Are "ITU-R601" and "CCIR 656" the same as CCIR 601? Did EU95 become DVB ?

--65.70.89.241 17:55, 6 September 2006 (UTC)

Uncompressed digital video bit rate[edit]

The article mentions the bit rate of roughly 400 MBit/s. By my calculation, standard definition digital PAL would have a bit rate of around 160 MBit/s at 8-bit per sample and 4:2:2 color sampling.

Agreed; the "400MB/s" comment probably hinted at the upper limits of those interfaces, rewriting that sentence would be good.--C xong (talk) 12:11, 24 June 2009 (UTC)

comparison with analogue formats[edit]

can someone make a section on this please? --AlexOvShaolin 19:44, 7 January 2007 (UTC)

digital vs electronic, video vs still[edit]

In the first paragraph the article claims Digital video was first used in television cameras and then goes on to explain the first VTR which was of course analogue. The next paragraph claims 1960s lunar probes used digital imaging, but in reality they were also analogue. Furthermore the latter sent still images, not video. Third, the article claims that the Sony Mavica was an example of digital video, but once again this camera stored still image as an analogue signal. It appears the author confuses rastered images and digital, still image and moving image all the time. This article needs a serious cleanup. Anorak2 (talk) 04:44, 17 November 2007 (UTC)

Done :) Anorak2 (talk) 04:56, 17 November 2007 (UTC)

I don't know how (or why), but the article returned to the state that warranted these complaints. I've reverted this wholesale rewrite of the history section because it was worse than uninformative--it was incorrect. As noted above, neither magnetic tape nor electronics imply digital. 98.202.51.77 (talk) 10:50, 17 March 2010 (UTC)

Here's a source that shows that digital video on magnetic tape arrived when Sony introduced the D1 videocassette in 1988. [1] It's counter intuitive given the binary nature of magnetic poles, but magnetic tape can be used to store both analog and digital signals; unless a video or audio source is converted to a digital signal, the magnetic tape is storing analog. Only recently did we have sufficiently sophisticated electronics to encode audio/video into a digital signal. 98.202.51.77 (talk) 04:47, 19 March 2010 (UTC)

Technical overview[edit]

This section needs a lot of work. There's some pov in there, some wrong information and a strange bias toward this one specific camera:

  • Motion Strobing: This line, "They can both shoot at 24 frames per second, which results in motion strobing (blurring of the subject when fast movement occurs)." is incorrect. That is not the definition of motion strobing (it's the definition of "motion blur"). Motion strobing as defined in Digital Compositing for Film and Video By Steve Wright, "an unpleasant artifact in which an object's motion takes on a jerky and "staccato" appearance due to the lack of appropriate motion blur."
  • Motion strobing is not unique to 24 fps or to progressive scan. Neither is motion blur. They're both simply more apparent at slower frame rates.
  • The article implies that motion strobing is a reason that "progressive scanning video cameras tend to be more expensive than their interlaced counterparts". The two are unrelated. (Progressive scan cameras tend to be more expensive because the chips have to read more data at a specific moment rather than getting to read half the data and spreading it out).
  • Panasonic DVX100: Why mention this specific camera and no other?
  • "Progressive scan camcorders such as the Panasonic DVX100 are generally more desirable because of the similarities they share with film." This is pov: The "film look" is not necessarily more desirable.
  • "Note that even though the digital video format only allows for 29.97 interlaced frames per second [or 25 for PAL], 24 frames per second progressive video is possible by displaying identical fields for each frame, and displaying 3 fields of an identical image for certain frames." This is a specific case applied incorrectly to the general (I suspect as a result of getting too much technical information from a single source that is specific to the camera mentioned above). There is nothing inherent to dv that requires a frame rate of 29.97. Only to NTSC. It is true that many cameras use a pulldown to record 24 frames with their native 29.97 hardware, but true 24p cameras exist and there's no reason hardware can't be built at any arbitrary frame rate.

If there is no objection, I'll take a crack at fixing this up. Focomoso (talk) 22:15, 18 June 2008 (UTC)


History[edit]

I suggest that this section (really most of the article in general) be more thoroughly referenced. There are numerous assertions that have no references at all. I'm really surprised that someone ranked this as a B-grade article. It's well written, but is it verifiable? I wish I could help, but I stumbled on this looking for an explanation of the various digital video file formats. I think the point of the encyclopedia is to be a resource for folks looking for general info, but it should also should give them the ability to go further by pointing to the sources of information. Best of luck with it MichaelKrobinson (talk) 17:35, 25 June 2008 (UTC)


A "fact" about PIXELs ?[edit]

I'd suggest it is untrue to state that pixels "have only one property - their colour". Surely, their shape is also a property - an important one in that non-square pixels are an essential determinant of the aspect ratio? Johncurrandavis (talk) 10:42, 23 February 2010 (UTC)

Unit of W and H[edit]

In the section, "Overview of basic properties", it is stated that the units of W and H are pixels. Another statement that could be made is that W is in units of pixels/line and H is in units of lines/frame. If W is 480 pixels/line and H is 640 lines/frame it follows that

pixels \ per \ frame = pixels/frame = 480 (pixels/line) \times 640 (lines/frame) =
 480 \times 640 (pixels/frame) = 307,200 \ pixels \ per \ frame.

On the other hand if you use pixels as units for W and H, you get the rather meaningless units of pixels square for pixels per frame. RHB100 (talk) 21:33, 30 June 2010 (UTC)

Towards an amendment...[edit]

In order to amend the untrue "fact" I allude to above, perhaps something along the lines of the following will be considered acceptable?..

Digital video comprises a series of orthogonal bitmap digital images displayed in rapid succession at a constant rate. In the context of video, these images are called frames. The rate at which frames are displayed is enumerated in frames-per-second (FPS).

Since each frame is an orthogonal bitmap digital image, it comprises a raster of pixels (short for "picture elements"), areas of the image meant to be too small to be perceived individually, but which determine the colour and brightness information of the whole image. Pixels have two properties: colour and dimension. The colour of a pixel is represented by a fixed number of bits. The more bits defining each pixel, the more subtle the variations in colour that are reproduced; this is called the colour depth (CD) of the video. Pixels are rectangular in shape (possibly square), and the dimensions of the pixels comprising each frame are a determinant of the aspect ratio of the video. For example, the frames of a PAL video 720 pixels across and 576 pixels high will, if the video aspect ratio is 4x3, be composed of rectangular pixels with proportions of 1.0666 to 1; but if the video aspect ratio is 16x9, then the pixels will be rectangular with proportions of 1.4222 to 1. (In other words, "widescreen" is in this case achieved by altering the dimensions rather than the number of pixels.)

Johncurrandavis (talk) 17:10, 5 July 2010 (UTC)
Cite error: There are <ref> tags on this page, but the references will not show without a {{reflist}} template (see the help page).