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A former member
Firstly, I apologise if this shouldn't be here, but as it is loosely TV related I'll post it anyway.

I'm hoping to buy a new camcorder (or more to the point, get one for Christmas). There are many different formats and I was wondering which is the best to get. The main problem with my current format (Hi8) is that the recordings have 'video lines' on them like this:

*

I've heard of MiniDV and Digital8 and these seem like the most likely options for me due to their pricing. Does anybody have any advice on which format to get, and whether these formats eliminate analog video disturbance?
noggin14,596 posts since 26 Jun 2001
Both MiniDV and Digital8 use the same digital coding standard, but they record on different tape formats. MiniDV is much more widespread and supported by more manufacturers than Digital8, and range from tiny palmcorders to near-broadcast quality devices. Digital8 camcorders are cheaper but lower end, though I think you can use Hi8 tapes in them, and may be able to replay your old Hi8 analogue recordings (worth checking this - I'm not certain)

The main difference in quality is the lens and camera bit, and the build quality, the recording quality is pretty much identical across the range, and won't suffer the analogue tracking / mis-alignment problems you seem to be suffering on Hi8.
peterrocket1,375 posts since 5 Sep 2001
Digital 8 cameras can play back the hi8 or 8mm tapes that you've previously recorded on, but it's more model specific if it will do this or not. Most should tell you in the specs.

One thing with digital8, you can use any 8mm tape to record on and you get the same results, so don't be fooled into Sony's marketing of Digital8 tapes.

The other thing, but it's to do with MiniDV, is that the tapes may seem expensive from the likes of Argos etc. but if you order online from broadcast tape suppliers, you can often pick them up for less than 3 (even if your only ordering about 3-5) and the tape quality is better than the likes you get in Argos too.
A former member
From a technical point of view, how come these digital tapes don't suffer interference? Surely, if recorded on tape, there will always be this risk?

Thank you for your help so far.
cwathen3,383 posts since 27 Dec 2001
Quote:
From a technical point of view, how come these digital tapes don't suffer interference? Surely, if recorded on tape, there will always be this risk?

There may well be signal loss in the playback system, and dropouts as the tape wears, but that won't affect what you see:

When playing an analogue tape, you are playing the signal back straight off the tape; that signal is therefore very complex and so and thus if you experience frequency drop off that will have a direct effect on the quality of the picture and sound. When playing a digital tape, the signal on the tape is simply a sequence of coded binary digits. Since there are only two states to identify between (as opposed to a continuous range with an analogue system), the raw signal on the tape is very much simpler (just a simple high or low signal, instead of an infinately variable one), and thus more robust. Even if the tape is wearing, as long as the decoder can still tell the difference between the two states, the data will still be retrieved and decoded correctly and therefore won't affect what you see on the screen at all.

And even if a bit should be transposed (i.e. a 1 is misread as a 0 and vice versa), there will almost certainly be an error detection and correction system built in.

You're going to need a very, very (very, very) worn tape before it affects the quality of the output.

To make this easier to grasp, I've knocked up a few diagrams in paint (and this is the basis of why digital signals are more robust than analogue ones). It's a bit more in depth than this, but this is basically what's happening:

*

Diagram A is a representation of what one of your existing analogue tapes would look like if you looked at in on a CRO (a very crude one I know). That is the signal - the video and audio is directly contained with in it. To get good quality playback, that signal must always look exactly like that each time you play it. If you played that tape a few hundred times and it wore, losses in the playback system would result in the signal coming off the tape to look different - to have been distorted. That directly translates into a drop in quality.

Diagram B is a representation of a typical digital signal. With digital, everything is encoded as 0's and 1's, and thus the signal has only two states. The signal is merely used to store dated which then has to be decoded. If all of the high states are taken as 1's and all of the low states as a 0, that is how you can encode the digital signal.

Now, suppose you play that tape a few thousand times and the signal gets distorted. Diagram C shows what it might look like. As you can see, it is very badly distorted. That however won't affect the output. Even though it may be recorded with two states, when playing back it's just looking for everything above a certain level to be read as a 1, and everything below a certain level to be read as a 0. If you take the line as the high/low split point, if you look at the signal you can see that the high and low values are still correct. In other words, the signal might be badly distorted but the decoder can still recognise a 0 and a 1, and thus it makes now difference at all to the quality of the output. The signal would have to be so badly distorted that it would have to cross the line before the data is being read back incorrectly. Thus, digital is generally a lot more robust.
A former member
cwathen posted:
Quote:
From a technical point of view, how come these digital tapes don't suffer interference? Surely, if recorded on tape, there will always be this risk?

There may well be signal loss in the playback system, and dropouts as the tape wears, but that won't affect what you see:

When playing an analogue tape, you are playing the signal back straight off the tape; that signal is therefore very complex and so and thus if you experience frequency drop off that will have a direct effect on the quality of the picture and sound. When playing a digital tape, the signal on the tape is simply a sequence of coded binary digits. Since there are only two states to identify between (as opposed to a continuous range with an analogue system), the raw signal on the tape is very much simpler (just a simple high or low signal, instead of an infinately variable one), and thus more robust. Even if the tape is wearing, as long as the decoder can still tell the difference between the two states, the data will still be retrieved and decoded correctly and therefore won't affect what you see on the screen at all.

And even if a bit should be transposed (i.e. a 1 is misread as a 0 and vice versa), there will almost certainly be an error detection and correction system built in.

You're going to need a very, very (very, very) worn tape before it affects the quality of the output.

To make this easier to grasp, I've knocked up a few diagrams in paint (and this is the basis of why digital signals are more robust than analogue ones). It's a bit more in depth than this, but this is basically what's happening:

*

Diagram A is a representation of what one of your existing analogue tapes would look like if you looked at in on a CRO (a very crude one I know). That is the signal - the video and audio is directly contained with in it. To get good quality playback, that signal must always look exactly like that each time you play it. If you played that tape a few hundred times and it wore, losses in the playback system would result in the signal coming off the tape to look different - to have been distorted. That directly translates into a drop in quality.

Diagram B is a representation of a typical digital signal. With digital, everything is encoded as 0's and 1's, and thus the signal has only two states. The signal is merely used to store dated which then has to be decoded. If all of the high states are taken as 1's and all of the low states as a 0, that is how you can encode the digital signal.

Now, suppose you play that tape a few thousand times and the signal gets distorted. Diagram C shows what it might look like. As you can see, it is very badly distorted. That however won't affect the output. Even though it may be recorded with two states, when playing back it's just looking for everything above a certain level to be read as a 1, and everything below a certain level to be read as a 0. If you take the line as the high/low split point, if you look at the signal you can see that the high and low values are still correct. In other words, the signal might be badly distorted but the decoder can still recognise a 0 and a 1, and thus it makes now difference at all to the quality of the output. The signal would have to be so badly distorted that it would have to cross the line before the data is being read back incorrectly. Thus, digital is generally a lot more robust.


Thank you - This has made everything much easier to understand. Very Happy

I've been doing a little more research and have come across an interesting article about a video camera's 'lux' rating. I have been lead to believe that 0 lux (ability to film without any light at all) is a good feature, but this article claims that having a 0 lux capability may affect the quality of images when filming in high-light conditions.

Can anybody with a 0 lux camera offer an insight into this?
A former member
Weather Man posted:
I know this sounds stupid, but is there a VC that has a CSO thing on it? Agin, a [ I]video camera[/I] . And it has to be available in the ROI?


Do you mean a chroma key function?
cwathen3,383 posts since 27 Dec 2001
Quote:
Not 100% on a chroma key is. PM me and explain!

Well you asked for it lol Wink

Chromakey is another term for CSO.

CSO stands for C olour S eparation O verlay - it's the technology which allows a solid colour to be electronically replaced with another image. Look no further than News 24 to see it in operation right now (9/10 weather forecasts are also done with a CSO).
peterrocket1,375 posts since 5 Sep 2001
You can get simple chromakey stuff on the likes of home basic video mixers and effects units - these are for about 400 or so, but any of the ones i've used, they're terrible and the quality is just fuzzy all around the image.
james20012,588 posts since 4 Sep 2001
I'm also looking to get a new camcorder after Xmas. Not that there's really anything wrong with my current one (it's a cheap JVC VHS-C model) but after using my cousin's Hi-8 over the summer, I want oent hat has some of the functionality that her camcorder has (including 16:9- the model I'm looking at does actally have extra picture on the sides on 16:9 mode, rather than most (including my cousin's) which just cut off the top & bottom of the 4:3 picture, meaning it is blurred & pixellated). Though I am looking at Digital 8 as well as Hi-8, I'm not aure as one of the things I'm looking for is the ability to paly back my aunt's old 8mm tapes (she used to follow us around with it everywhere, yet we never saw the tapes. She has a box full of them, but her camcorder broke in 1997 and she never bought a new one, so we can't play them) but I'm not sure if all Digital 8 models can do this- I know some can, and I know Hi-8 ones can as well.