Talk:HDV
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Does anyone know how to do tables in Wikipedia so that you can also put in wiki hyperlinks?
The specification section of the HDV article needs hyperlinks but due to using the html 'pre' tag (in order to acheive two culumns) the hyperlinks are ignored.
Ericross
What the hell do terms like 'chocante', 'joinha', and 'batata' mean? Shouldn't they be explained here? --JeffSela
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[edit] HDV Compression
This section needs a little more data: exactly what is the bitrate of the compressed audio, and is there any sourcing data for the claim that (in the original version) the audio compression fools even people who claim to hear artifacts in 320kbps MP3 or (in my edited version) that the resulting audio is almost identical to the uncompressed audio? Are there any disputes about that? cluth 08:32, 5 February 2006 (UTC)
[edit] Horizontal vrs Vertical resolution
"the spatial resolution of the human eye is less sensitive to differences in horizontal resolution than vertical resolution.
Do we have a reference for this? I've heard it once before somewhere, but I am skeptical. I thought the reason for dropping horizontal resolution was that the vertical resolution was not truly 1080 due to the effect of interlace, and pixels are used most efficiently if horizontal and vertical resolutions match. (In other words, you won't notice the loss because the picture is already blurred vertically, and 1440 pixels blurs it horizontally to the same extent.) Algr 08:02, 20 February 2006 (UTC)
- I have observed that horizontal resolution is more important than vertical, because most images contain a lot of prominent vertical edges such as grass, trees, fences, etc. The argument for vertical blurring by line structure is no longer valid, now that most (plasma and lcd) displays present a sampled image in both directions. In the old days of the CRT, the picture was presented as samples vertically, but as a continuous function horizontally. This remained true even on digital broadcasts, since the video waveform was reconstructed to a continuous analog waveform by simple filtering before it reached the CRT. Now, resolution is lost in both directions because the image is presented as samples without the reconstruction filtering that is theoretically needed. We will not see the true resolution of HD until displays are available with at least twice the resolution of the signal in both directions (3840 x 2160 pixels) with digital reconstruction filtering, a fact that is not widely recognised. It is for this reason that SD video looks better on modern plasma displays than it ever could on CRT's - the image is finally being digitally reconstruction filtered prior to display, rather than just presented as samples (the samples are not the image, they are, strictly, a mathematical encoding of the image according to Nyquist theory). In practice, many other things (lenses, CCD's, processing circuits) reduce sharpness by causing a roll-off in spatial frequency response (also known as modulation transfer function), such that the full resolution of any video format is rarely realised. This is why movies look better than most video - they are shot to a higher resolution than the video, using the best lenses, and then re-sampled, giving a result with less roll-off in spatial frequency response as well as less aliasing. --Lindosland 12:26, 11 November 2006 (UTC)
My understanding is that the designers of HDV decided to reduce the horizontal resolution a little in order to stay within the 25Mbits/sec of the DV recording standard. This is acceptable since HDV camcorders do not represent the high-end of HD and so will not have the lenses needed for full 1080 line quality. Reducing both vertical and horizontal resolution to achieve the same end would have effectively created a new standard rather than just requiring simple interpolation in one direction. --Lindosland 12:38, 11 November 2006 (UTC)
[edit] Inclusion of Panasonic HVX200 camera
I refer to the recent reversion, and my attempts to scale down (not entirely exclude) mention of the Panasonic HVX200 camera in the History section.
This camera is NOT an HDV camera. Why then must an entire paragraph be devoted to it in the "history of HDV"? I do believe it is relevant, but only insofar as it shows that a major player in the "prosumer" camera market decided NOT to go for the HDV standard, but try a different approach altogether.
It is relevant, but I think it is confusing to include it as it currently stands, because the average reader may assume that this camera is a slightly different kind of HDV camera.Anselan
[edit] HDV vs. brodcast HDTV
The comparison to (ATSC) broadcast HDTV were, in my opinion, off the mark. The bitrate of ATSC is limited to ~19 Mbps, whereas HDV/1080i is 25Mbps. But that is ONE factor out of many more, equally important factors. The HDTV-broadcast chain includes some pre-processing (deinterlacing, spatial filtering, de-noising, etc.), and the broadcast MPEG-encoder operates under a different set of rules (closed GOP, GOP-size, etc.) The conclusion is that while HDV/1080i's bitrate exceeds ATSC, it does not necessarily mean a superior picture.
- My intention was to make clear the fact that any motion artefacts on HDV are absolutely negligible compared to the very obvious MPEG artefacts that viewers in the UK are familiar with on SD (Freeview) broadcasts where the bitrate is only 2 to 4Mbits/s. This is partly because any defects on HD will be on a finer scale, but also because the bitrate allocated to these broadcasts tends to be too low. --Lindosland 12:05, 11 November 2006 (UTC)
The comments about Apple Intermediate Codec being very lossy and giving no real time performance is simply untrue.
[edit] Choosing your ideal HDV Camcorder
Hi I've got an article about choosing an HDV camera for certain purposes: http://www.creativevideo.co.uk/public/articles.php?article=10 Fuutott 09:25, 25 October 2006 (UTC)
[edit] Deinterlacing and web section
The deinterlacing and web section is rather poorly written to be frank. For example, it claims that PC's don't support interlaced content properly which AFAIK isn't true since a number of options are available for realtime deinterlacing including hardware accelerated. And of course, PC users do have the option of doing non-real time deinterlacing. I don't know how these compare to plasma but they are there. Another problem section:
- It is not impossible to achieve good results though, if the correct methods are used to deinterlace the footage. See the examples on this page. The showcase material is of course all from film, and therefore 24p to begin with, avoiding the deinterlace problem.
This appears to be saying it's possible to achieve good results (which isn't a surprise), look at the examples. But wait, the examples weren't actually deinterlaced... Say what?
I actually question whether this section is needed and if it is, in such depth. This appears to be related to HD video and interlacing and the web in general. Not HDV specifically. As such, I would suggest it's best covered in another article Nil Einne 10:54, 23 December 2006 (UTC)
[edit] Inaccuracies and Redundancies
I have a few suggestions as to how we may make this article even better.
- As somebody mentioned above, if a camera is not true HDV, then it should be omitted from the article. e.g. the Panasonic DVCPRO HD cameras.
- The discussion on MPEG 2 should only go so far as to say that HDV uses Long GOP MPEG-2 at 25mbps, and any other technical details related to recording MPEG 2 to tape (i.e. tape dropout, etc). Any discussion of MPEG-2 should use the standard MPEG-2 nomenclature, i.e. I frames, B frames, P Frames, where relevant. The term "key frame" should not be used in this article at all, seeing as "Key Frame" has a different meaning depending on the context, and in the context of Video it can refer to animation key frames as well as I frames. The structures and other in-depth technical details of MPEG 2 should be referenced to the article on MPEG 2.
- The "Overview" section is probably a little too broad for an overview section. There are several redundancies between that section and the "HDV Compression" section.
- Perhaps the "Notes regarding specific camcorder models" section should be expanded to include Canon's 24F and 30F (instead of 24P and 30P) formats on their pro camcorders (XH-A1, XH-G1, XL-H1). Once I get my XH-A1 and have worked with it a while, I will add to this section.
- Perhaps we should add a section about HDV in relation to other HD formats such as HDCAM and AVCHD.
- I agree that the "Deinterlacing and Web" section should probably be removed, seeing as it has very little to do with actual HDV and more to do with HD Video and Non-linear editing.
These are just some suggestions. Opinions? If there is no feedback on these, I will begin implementing some of them soon.
Dormous 16:15, 12 January 2007 (UTC)
I agree with Dormous' changes. Perhaps we should consder creating a sort of HD Format disambiguation page. There seems to be alot of splill over from one page to the other and it makes some of the pages pretty confusing. The DV page for example talks about DV, HDV and DVCPROHD all at once even though the later two have thier own pages.
