Thank you for being a valued part of the CNET community. As of December 1, 2020, the forums are in read-only format. In early 2021, CNET Forums will no longer be available. We are grateful for the participation and advice you have provided to one another over the years.

Thanks,

CNET Support

General discussion

Hard Drive Camcorders with 7.5 hours record time

Oct 25, 2005 3:41PM PDT

I visited Circuit City tonight and saw 3 JVC camcorders with internal hard drives. 2 with 30 gig and 7.5 hours of record time and 1 with 20 gb with 5 hours record time. Price ranged from $854 to $759. I've been trying to decide between tape and DVD, but this is new to me. Has anyone tried these or heard any pos or neg reviews?

Discussion is locked

- Collapse -
My guess is that mini-DV is still superior. I'm basing that
Oct 25, 2005 6:27PM PDT

on two thoughts. First, mini-DV uses roughly 13.5 gigs to store 60 minutes of video. That's a LOT more than these JVCs are storing. Second, the mini-DV tape serves as a form of long term backup for the video. You won't have that with these cameras. You'll have to download quickly to make room for additional recording.

- Collapse -
Disagreement from a JVC Everio GZ-MC50 owner
Oct 26, 2005 2:14AM PDT

First of all, to rate quality of video based on file size is as ridiculous as comparing processors strictly based on clock speed. That doesn't tell the whole story!

The JVC hard drive camcorders record video on the hard drive in MPEG-2 compression (the same compression used in DVDs). It should come as no surprise then that DVD camcorders also use MPEG-2 compression. This is a higher compression than DV, so of course the files will be smaller. The key difference between MPEG-2 and DV is that DV is much easier to edit, since it is a "loose" compression format, and thus much easier on your computer's processor. MPEG-2 compresses video down to ~ 1 MB/s while DV is ~ 3 MB/s, and as such DV is easier to decompress and edit on the fly.

Second, why would you want to have long term backup of your video on miniDV tape (which can only be played in your camcorder), when you can backup on DVD?

It's true that you have to upload your video from the JVC Everio camcorders to your computer in order to keep the hard drive empty for new video that you want to shoot. The 30 GB versions hold 7.5 hours of DVD quality footage though! How often do you shoot 7.5 hours of continuous footage?!? Most likely, you will have access to your computer long before you run out of room.

Whenever I have roughly an hour of video on my JVC camcorder, I upload it to my computer and burn it to DVD. Since the camcorder stores the video in MPEG-2 format, there is no encoding required during the DVD burning, and so the whole process takes me 10 minutes. There's your long term backup storage. Then when you have time, you can go back and upload the video from the DVD and edit it in Sony Vegas (or your application of choice) and then burn it to DVD again as a polished work.

- Collapse -
Disagreement to JVC Everio owner
Oct 26, 2005 2:56AM PDT

You don't seem to understand the "real" benefit of a mini-DV tape as both a record format and a storage format. First, MPEG2 format is already highly compressed. Most video editing software will uncompress this MPEG back into DV for editing, thereby bumping the quality down a huge notch. If your editing software allows input of, and editing in MPEG format, you are editing in a highly compressed format (lesser quality). But, if you can't see the loss of quality, then this method is fine. Second, storing a project on a DV tape allows storage in full-quality DV format, not the highly compressed format that you get when storing on a DVD. Again, to re-work this DVD material requires one to do as stated above. Thus, you work with lower quality material. If working with low quality MPEG footage is sufficient, then you will be happy with downloading from your camcorder via USB, which does not download full-quality DV footage. Basically the simple rule: Junk in, junk out.

- Collapse -
The "real" benefit...
Oct 27, 2005 4:40AM PDT

I think that it is great that you put "real in quotes, since it really does depend on the user. Judging by the initial enquiry, we are not talking about power users. We're talking about average consumer users (who usually don't re-edit their video, and likely do not edit all of their video). For me, the quality that I get with 1.33 megapixel video compressed to MPEG-2 is in perfect harmony with being able to immediately burn it to DVD for viewing and sharing. I have to admit that my editing needs are simple (cutting and pasting, trimming, color balance and contrast, transitions, audio dubbing - nothing real fancy). The quality of the footage I get from my camcorder is not as good as that of a 1.33 megapixel miniDV camcorder (when viewed in native DV format), but don't forget that the goal is to eventually move that DV footage to DVD (and thus MPEG-2). Once this happens, the quality of footage is nearly indistinguishable (with miniDV having a slight advantage because of VBR encoding vs the CBR encoding done realtime in the JVC camcorder). Thus, since my editing needs are simple, and I don't need to de-encode and then re-encode, MPEG-2 recording suits my needs just perfectly.

If you re-read my post that you replied to, I think you will realize that my critique was aimed at basing a quality comparison strictly on file size. You CANNOT say that because DV stores the video in a file three times the size of MPEG-2, that the video quality is better. If I give you a 100k pixel sensor, and you record from it into DV format, while I record from a 1M pixel sensor into MPEG-2 format, I will have better video quality than you. Junk in, junk out as you say. So you have to take into consideration the optics of the camera, the resolution of the sensor, and the limitations of the recording format in order to make an informed decision as to whether an MPEG-2 camera or a DV camera is better. To satisfy you, I fully acknowledge that given identical optics and sensors, the video will look better in DV format than in MPEG-2. But as I mentioned above, once the DV is encoded to DVD, it too is in MPEG-2 and has suffered similar losses in quality in getting there.

At the end of the day, the user has to determine (based on their own needs) which is better for them. For me, the convenience of recording to MPEG-2 outweighs the limitations on editing.

- Collapse -
If you assume simplicity, you would get a camera that
Oct 27, 2005 6:12AM PDT

records on DVD rather than the JVC unit. Let's say you record 7 hours of mpeg-2 video. You've now got to know many things. How to upload it to the computer. How to break it down so that 7 hours will fit on DVD. How to burn the DVD using the mpeg-2 format as your source. Except for the upload to the computer, these issues are as complex as, or more complex, than the issues involved in using mini-DV. This is not a camera for beginners.

- Collapse -
I don't think you're reading what I'm typing...
Oct 27, 2005 8:05AM PDT

Maybe you should quote what is in my message before you reply to it, because I'm not sure that you are reading very thouroughly. I'm trying to be as straight to the point as I can be! I never said that using the JVC hard-drive camcorder was simpler than using a miniDV camcorder (check my posts if you like). What I said was "... my editing needs are simple (cutting and pasting, trimming, color balance and contrast, transitions, audio dubbing - nothing real fancy)".

I never said that my aim was simplicity. I said that using the hard drive camcorder was convenient for me. Of course that depends on the individual, but I believe I was clear on that point too: "At the end of the day, the user has to determine (based on their own needs) which is better for them. For me, the convenience of recording to MPEG-2 outweighs the limitations on editing." In fact, I never accused miniDV of being complex. I merely implied that I found it an inconvenient medium and format for my purposes.

- Collapse -
You are arguing with physics. The amount of data coming off
Oct 27, 2005 6:04AM PDT

the camera's sensor is a known. The more of that data you can capture, the better off you will be. That's not a matter of opinion, and it's not the same as differences in CPU speed.

For 7.5 hours of video, a mini-DV will capture and store about 98 gigabytes. It will, of course, need more than one tape to do this. The JVC drive will store 30 gigabytes. That means that the mpeg-2 compression is throwing away more than two thirds of the data that the camera is supplying. If all you want is a DVD from the camera with no editing, that may be fine. However, you will be paying more and getting less (assuming that the JVC camera is more expensive than a comparable mini-DV camera). You will also have no backup of that fragile DVD, unless you make a second copy, and you will find it difficult if you wish to go back later to extract a clip. You are also at the mercy of the JVC compression algorithms although those might be standard code.

If you want to edit any video you shoot during the life of the camera, you will be working with a severe handicap because you've only got one third of the original information that came from the camera.

The tapes are a far more reliable form of backup than a DVD. DVDs can be destroyed almost instantly, and their shelf life is much more uncertain. The tapes are also much cheaper than any other form of backup.

You can pop in a new mini-DV anytime you need to and move on, while the hard drive of the JVC unit will need to be tethered to a computer. I, for one, don't need that kind of hassle when I'm trying to focus on getting good video footage. If that hard drive does fill up, you are SOL. It is also likely that the power needed to run that drive will drain your battery more quickly.

Finally, a hard drive in a portable device is far more prone to a crash which causes the loss of all data on the drive than is a tape drive.

Hard drives can be a good idea. However, they should be an addition to a tape based camera, not the sole form of storage. They should also store the full set of DV data coming from the sensor, not a compressed form. Cameras like the Canon XL2 support the approach to hard drives that I just described.

- Collapse -
I'm not arguing with physics.
Oct 27, 2005 9:16AM PDT

In fact, physics is my profession. If anything, this discussion lies in the realm of mathematics (i.e. mathematical transforms... after all, that is the basis of compression algorithms). I think you will want to be clear on that first before proceeding with this discussion.

Assuming that all other factors are equal, you are correct that the DV format preserves more of the original video signal from the image sensor than the MPEG-2 format. However, everything else about your posts suggests that you do not have a good understanding of compression, and that you are not reading carefully before replying.

Let's address some of those misconceptions.

Both DV and MPEG-2 are lossy compressions. This means that some information is lost when the data is compressed to each of these formats. Also, MPEG-2 is more lossy than DV. So far, I believe we are in agreement.

"For 7.5 hours of video, a mini-DV will capture and store about 98 gigabytes. It will, of course, need more than one tape to do this. The JVC drive will store 30 gigabytes. That means that the mpeg-2 compression is throwing away more than two thirds of the data that the camera is supplying."

This is where you go wrong. Compression is not merely about throwing data away! That is a gross and erroneous simplification. Compression is about expressing data in a more succinct form. This can be done without discarding any information (lossless compression), but will not result in as small a file as a lossy compression.

The ultimate goal of lossy compression is to succinctly express the data AND discard extraneous information. A compromise is typically struck between how much information is discarded and how small the file needs to be. Thus, an MPEG-2 file being more than three times smaller than a DV file DOES NOT mean it contains three times less information. If at this point you still believe that to be true, then you are truly misunderstanding the principles behind compression algorithms.

A good example of the concepts involved with compression exists in the world of mp3s. Compare a CD track to an mp3 track. An mp3 is merely a compressed representation of the digital data stored on the CD. The data on a CD has a bitrate of 1378 Kbit/s or 1411 Kbit/s. For the sake of simplicity, let's say 1400 Kbit/s. A high quality MP3 can be achieved at 320 Kbit/s. Does this mean that the MP3 has lost more than four times of the data contained in the original CD track? NO. The MP3 represents the data by transforming it from the time domain to the frequency domain, and dropping frequencies that have little or no impact on the human listening experience. The lower the bitrate you encode an MP3 at, the more significant the frequencies that are dropped. I suggest reading up on how mp3 compression and Fourier Transform algorithms work.

"If you want to edit any video you shoot during the life of the camera, you will be working with a severe handicap because you've only got one third of the original information that came from the camera."

I think I've already established that the above comment is WRONG (specifically the part about "one third of the original information"). It is actually very easy to extract clips from DVDs (there are numerous applications that are capable of it), and decoding to DV from MPEG-2is not nearly as processor intensive as encoding to MPEG-2 from DV. You suffer some minor quality loss because of the encode to DV (since it too is a lossy format), but I have found that there are some excellent algorithms for this that do not noticeably impact the image quality.

"You will also have no backup of that fragile DVD, unless you make a second copy.... The tapes are a far more reliable form of backup than a DVD. DVDs can be destroyed almost instantly, and their shelf life is much more uncertain."

You must be employed by a tape manufacturing company. I'm not sure what DVDs you use, but mine aren't that fragile at all. In fact, I've never had a DVD player eat a DVD. But I've definitely had a camcorder eat a tape on numerous occasions. If you are careless, then obviously either one can be destroyed relatively easily. I would like to criticize the makers of tapes and DVDs alike for designing a product that melts in fire!

"The tapes are also much cheaper than any other form of backup."

Where do you buy your DVDs? A quick glance at prices on the internet tells me that miniDV tapes go for ~ $5 a piece. I can get blank DVDs for $0.30 a piece. How do you figure that tapes are much cheaper than any other form of backup?? BTW, I can also write to DVD faster than you can write to tape.

"You can pop in a new mini-DV anytime you need to and move on, while the hard drive of the JVC unit will need to be tethered to a computer. I, for one, don't need that kind of hassle when I'm trying to focus on getting good video footage. If that hard drive does fill up, you are SOL. It is also likely that the power needed to run that drive will drain your battery more quickly."

Yes, I like the fact that I can go 7.5 hours without having to switch tapes. That is fantastic. And I have a laptop, so I'm not tethered to my computer, it's tethered to me. What happens if you forget to bring enough tapes? Then you're SOL and I've still got my 7.5 hours of recording time. I've got a two hour battery and a one hour battery, and they last as long as they are rated.

"Finally, a hard drive in a portable device is far more prone to a crash which causes the loss of all data on the drive than is a tape drive."

That's why the drives have a G-force sensor in them, so they shut off if the camera is dropped. Don't forget, tapes can be eaten (especially if you don't clean your camera heads regularly - something you don't have to do with hard drive based players), so they aren't without risk of "crashes".

"Hard drives can be a good idea. However, they should be an addition to a tape based camera, not the sole form of storage. They should also store the full set of DV data coming from the sensor, not a compressed form. Cameras like the Canon XL2 support the approach to hard drives that I just described."

OK, be realistic here. We're talking about consumer level camcorders, not prosumer or professional! Canon XL2 ~$5000 vs JVC Everio GZ-MC50 ~$1000. A bit of a price/class discrepancy, don't you think?

- Collapse -
The term 'lossy' means that information is lost. That is,
Oct 27, 2005 10:15AM PDT

the original signal cannot be reconstructed. The term 'lossless compression' means that compression has been done, but that the original can be reconstructed. Since you admit that mpeg-2 is a lossy compression, your rather long explanation loses steam at that point. Mpeg-2 is far more lossy than DV, and, as such, is a vastly inferior source of video information. To argue otherwise is just silly. It is akin to arguing that jpeg is comparable to tif or raw formats. No video professional will choose mpeg-2 over DV as a video source. If mpeg-2 is equivalent to DV, why would the camera companies be recording DV on their tape? They could record mpeg-2 and significantly lengthen the recordings that a tape will accomodate. They use DV because they do not want to degrade the video data coming from the camera.

Attempting to use mp3 as an example simply exposes the fallacy. I don't think any serious professional would argue that mp3 is a good source of audio. mp3 compression is done by retaining the sounds that are the loudest, and that tend to mask more subtle sounds. It is not a good audio format. It's main virtue is that it allows far more material to be stored on devices with limited capacity.

You seal your naivety by arguing that DVD storage is as good as tape. It seems that you know less about DVD longevity than you do about video and audio compression. Arguing with such nonsense is an exercise in futility.

- Collapse -
You've missed the entire point...
Oct 27, 2005 11:29AM PDT

You refer to professionals choosing video formats, but you have missed the point that this is regarding CONSUMER cameras. I keep enphasizing that, but you still manage to gloss over the point. Anyone considering buying a JVC hard drive camcorder is NOT planning on using it for professional videography!

"If mpeg-2 is equivalent to DV, why would the camera companies be recording DV on their tape?"

You really need to read more carefully. I never said that MPEG-2 is equivalent to DV. In fact, I said that MPEG-2 is more lossy than DV. Read back in my posts. However, since you are on a soapbox here and consider MPEG-2 to be FAR inferior to DV, why don't you check out the HDV standard? Hmmmmm.... I believe that is based on MPEG-2 compression! Seems the camcorder companies and industry experts have formed a consortium that supports the use of MPEG-2 in high definition video capture. And there are already cameras coming to market using this format.

MP3 compression is NOT done by retaining the sounds that are loudest! MP3 compression is achieved by transforming audio from the time domain to the frequency domain. Fourier Transforms are one way of accomplishing this transformation. I never claimed that MP3 audio was a "good audio format", I only pointed out the "fallacy" in your logic that a file compressed three times as small contains three times less information. This shows your ignorance (in addition to the fact that you cannot discern between physics and mathematics).

You regurgitate information that I already stated on lossy vs lossless compression, attempting to sound knowledgeable, when in fact you exposed your own ignorance on the subject by stating that "For 7.5 hours of video, a mini-DV will capture and store about 98 gigabytes.... The JVC drive will store 30 gigabytes. That means that the mpeg-2 compression is throwing away more than two thirds of the data that the camera is supplying." Anyone who knows anything about compression knows that this is false. Bigtime. The two formats compress in very different ways, and the loss of information cannot be summarized strictly by file size.

You can't cover up your ignorance with meaningless rambling. I understand that you have a desire to sound intelligent and in the know, but you are doing a disservice to anyone looking for information on the subject by posting this drivel. Debate on a point to point basis with valid fact-finding, or don't do it at all.

Up until now, I have merely attempted to be informative. I can see that you would rather engage in a flame war, and as such, pursuing this conversation further is useless.

- Collapse -
Perhaps then, you can educate me/us. Just exactly how much
Oct 27, 2005 3:23PM PDT

data, as a percentage, is lost by mpeg-2 compression versus DV. Please either document your answer, or cite sources.

You are merely repeating what I said at the outset. If all you want is DVD as output, perhaps mpeg-2 storage is OK. However, if you ever hope to edit your material, you are best off using mini-DV. If you look at my original post, I think that is what youn will find.

While I have been familiar with Fourier analysis for over 40 years, I prefer to put things into English so that they can be understood. The audio pros that teach me tell me that mp3 basically operates by capturing the loudest sounds. Please provide a link to your source that says this is not the case. Mere assertions are easily made. It's time to back them up.

- Collapse -
PS: You may also want to comment on the problems associated
Oct 27, 2005 3:26PM PDT

with using a lossy source for editing, and then reencoding it in a lossy format. Some may understand what this means by thinking about what happens to jpeg sources that are resaved as jpegs.

- Collapse -
No disagreement here...
Oct 28, 2005 2:38AM PDT

Decoding a source (video or otherwise) and then encoding it again (presumably after editing) does result in an extra loss of quality. This occurs with DV and MPEG-2 and any other lossy compression. The worst losses occur when you decode from one format and then encode to a different compression format. Because the two compression schemes are different, the algorithms will have thrown out different types of information each time, thus increasing your losses! That's why I prefer to do just simple editing (editing that does not require conversion) on my MPEG-2 files. This works for me because my needs are simple. Someone with much more extensive editing needs (or wants) should stick with DV, especially since it is such a ubiquitous format for editing.

- Collapse -
ALL mpeg-2 editing requires conversion before ANY editing
Oct 28, 2005 9:08AM PDT

can be done. You CANNOT directly edit an mpeg-2 file. If you don't understand that, then you don't understand what mpeg-2 is. I am fresh from a seminar on video editing and encoding where that message was reinforced again by those who REALLY, unquestionably understand the subject.

Also, please tell us the percentage of loss in a DV file versus an mpeg-2 file.

- Collapse -
You're capable of looking this up too
Oct 31, 2005 4:45AM PST

"Also, please tell us the percentage of loss in a DV file versus an mpeg-2 file."

You can start doing a search of your own, or perhaps talk to your "industry expert friends", and determine this information. I only have so much time in a day to waste looking for statistics to satisfy your never ending quest for argument.

"ALL mpeg-2 editing requires conversion before ANY editing can be done. You CANNOT directly edit an mpeg-2 file. If you don't understand that, then you don't understand what mpeg-2 is. I am fresh from a seminar on video editing and encoding where that message was reinforced again by those who REALLY, unquestionably understand the subject."

You don't understand the nature of the editing that I am doing if you think that ALL editing of MPEG-2 requires conversion. Simple cutting and pasting can be done frame accurate, and requires no conversion. Editing the audio stream requires no conversion of the MPEG-2 video (you do have to convert the audio, but this only requires demuxing of the audio, and then converting the audio for editing. So don't start preaching to me that I don't understand the subject. I do the editing. If it required conversion, I would know, since it would take my computer a significant amount of time to do the converting.

- Collapse -
I'm sorry, but you are still showing that you don't get it.
Oct 31, 2005 7:23AM PST

I asked you for the percentages because you argued that mpeg-2 does not lack two thirds of the information that DV has. It is irrefutable that a a 98 gig DV file holds the same length of video as a 30 gig mpeg-2. You argued that the mpeg-2 does not contain two thirds less information than DV because it is compressed, and the apparent loss of data can be at least partially reconstructed. That assumes that you know what the percentages are. Since you do not, your argument that the apparent two thirds loss of data is not real cannot be sustained. You simply do not know how much information is lost in an mpeg-2 file versus a DV file.

Consider further that the DV file is also compressed. Therefore, when it is uncompressed, it will yield far more than the original 98 gigs. Mpeg-2 compression throws away a lot more data than DV. This is data that cannot be reconstructed because, as I pointed out, the compression is lossy.

It, therefore, seems to me, that it is fair to say that mpeg-2 is missing a lot more information than DV, and I see no reason to assume that the difference is not reflected by the relative file sizes. Those are all we have, and those stongly suggest that DV has two thirds more data than mpeg-2. You can continue to argue that I do not understand mpeg-2 compression, but, in the absence of data to back up that assertion, I don't see how you can demonstrate the truth of your claim.

One thing that is abundantly clear, is that you do not understand the compression within mpeg-2 files. If you did, you would not continue making the statements that you do. If you want to understand this, you should probably do some research on the types of frames within an mpeg-2 file. Once you do that, you will begin to understand why even a simple cut and paste cannot be done on a 'frame accurate' basis. Information within an mpeg-2 file does not fully describe every frame. Therefore, the file must be converted to a form like AVI before a cut or paste can be done. That is why your continued assertion that you can do this simply broadcasts a lack of understanding.

I'm sure you know that 'you can lead a horse to water, but....'. I will simply say again, that All editing of mpeg-2 files requires conversion. However, I will concede that if you start with two separate mpeg-2 clips, you can indeed concatenate them without resorting to conversion. You simply cannot cut one clip into multiple clips without conversion. You may find software that appears to do this, but the required conversion will be done internally by the program. You won't necessarily see it, but that doesn't mean it's not done. It's also possible that it's done very quickly. I never said the entire mpeg-2 file has to be converted. I said conversion must be done before certain operations can be performed.

Editing the audio stream is entirely possible. The audio is not a part of the mpeg-2 compression process, and is easily separated out into a separate file. However, I am not at all sure that the edited audio can be reinserted into the mpeg-2 file without substantial additional processing.

- Collapse -
I will try...
Oct 28, 2005 2:42AM PDT

"Perhaps then, you can educate me/us. Just exactly how much data, as a percentage, is lost by mpeg-2 compression versus DV. Please either document your answer, or cite sources."

I don't know the percentages off the top of my head. I'm not even sure if this information is readily available, but it must be documented somewhere. If I come across it, I will post it here. For now though, keep in mind that contrary to what you stated in your "You are arguing with physics" post, the size of the file alone does not indicate how much information has been kept or lost (see my exceedingly simple analogy below).

"You are merely repeating what I said at the outset. If all you want is DVD as output, perhaps mpeg-2 storage is OK. However, if you ever hope to edit your material, you are best off using mini-DV. If you look at my original post, I think that is what youn will find."

If you read my reply to your original post, you will find that I wasn't trying to argue that MPEG-2 was better than DV. I made two assertions in that reply. The first was that your understanding of compression was incorrect. If you want to compare MPEG-2 and DV compression, you first need to understand compression. The second assertion was that I disagreed with your view that miniDV is a superior form of long term backup. That's it. I never disagreed that miniDV is best if you are planning to do editing. In other posts, I merely asserted that my needs are such that I only require simple editing (scene trimming, simple transitions, cutting and pasting, and audio dubbing) which can be done with MPEG-2.

"While I have been familiar with Fourier analysis for over 40 years, I prefer to put things into English so that they can be understood. The audio pros that teach me tell me that mp3 basically operates by capturing the loudest sounds. Please provide a link to your source that says this is not the case. Mere assertions are easily made. It's time to back them up."

Everything I have said is all easily verifiable by doing quick internet searches on these topics. As always, you have to be careful with information found on the internet (ie. read with a grain of salt, and pay attention to your sources), but there is lots of good, accessible information on these subjects.

If you want to know about MP3s, try

http://en.wikipedia.org/wiki/Mp3

Specifically, it says in the overview:

"The MP3 format uses, at its heart, a hybrid transform to transform a time domain signal into a frequency domain signal".

This is the essence of your compression. Because of the sinusoidal nature of most musical sounds, music can be represented more succinctly in the frequency domain. If all sounds were simple monotones (only representing a signle frequency), this would provide a perfect solution. Unfortunately, some sounds (in particular, impulses) contain many frequencies. A perfect impulse actually carries an infinite number of frequencies. In music, this manifests itself in sudden and intense sounds (cymbal crashes for example).

To digitally represent all of the frequencies contained in these intense sounds would require an immensely large file, and would defeat the purpose of compressing it in the first place. So, psychoacoustic (the study of the human perception of sound) analysis is performed to analyze which frequencies are the most important to human perception in that particular sound, and the rest are discarded (this is where the lossy nature of MP3s comes from).

Part of the psychoacoustic analysis involves discarding lower volume noises that we won't be able to hear over the louder volume noises. I am not accusing your audio pro friends of being wrong about that fact, but I think you are misunderstanding them if you believe that this is the biggest source of the compression achieved with MP3.

The simplest (plain English) example I can give on how a transformation can simplify data is this: I will give you two statements, one uncompressed and one compressed.

Statement 1:
"I have five apples. Apple One is a Granny Smith. Apple Two is a Macintosh. Apple Three is a Macintosh. Apple Four is a Macintosh. Apple Five is a Macintosh."

Statement 2:
"I have five apples. Apple One is a Granny Smith. The rest are Macintoshes."

As you can see, the second statement is more succinct than the first. In this particular case, this is lossless, but that's not the point of the illustration (and it is just an analogy, don't read into this too literally). The point is that I can express the information in a more compact form just by changing how I represent that information. In many compression algorithms, the biggest savings comes from this. In fact, in lossless compression algorithms (which I've seen achieve compression ratios of 3:1) this is where all of the savings comes from.

- Collapse -
'I don't know...it must be documented somewhere' That is the
Oct 28, 2005 9:19AM PDT

most useful part of your post. I ask for detailed, documented specifics, and you respond with simple examples. Stories and hand waving if you will.

'discarding lower volume noises that we won't be able to hear over the louder volume noises'

I think that's pretty close to what I said.

I'm sorry, but I don't have the patience to deal with someone who continues to assert their point without offering the documentation and evidence to back it up. This is particularly true when your earlier post indicates that you don't understand mpeg-2, and you come very close to saying what I said about mp3.

- Collapse -
I'm not sure what you're after here...
Oct 31, 2005 5:48AM PST

"'I don't know...it must be documented somewhere' That is the most useful part of your post. I ask for detailed, documented specifics, and you respond with simple examples. Stories and hand waving if you will."

I responded with simple examples, because you said that you try to understand things in plain English. Your comment that since DV contains three times more information than MPEG-2 because DV files are approximately three times bigger also suggests that you require plain English explanations. If you don't understand why that statement that you made is fundamentally flawed, then you are not equipped to read technical descriptions of how these algorithms work. As such, my responses were completely appropriate. As far as the detailed, documented specifics, I believe the cliche is "the pot calling the kettle black". In fact, in response to your request for information, I provided you with a link that had a detailed and accurate description. Convenient how you glossed that over. It should be noted that you have not once cited any source of information or given any kind of documentation, but have instead relied on encylcopedia yourselfica and hidden behind "industry expert" friends with the "they say" argument, which holds no water.

"'discarding lower volume noises that we won't be able to hear over the louder volume noises'

I think that's pretty close to what I said."

You quote with the utmost journalistic integrity. Convenient how you left out the part where I said that is NOT the primary source of information compression in the algorithm. You gloss over significant details in an attempt to try to hang on to "i'm right" instead of actually reading what is there and processing it in an intelligent manner. I am happy to discuss and debate with you on academic merit, but not if it is going to be a pointless, circular argument of semantics and rhetoric.

"I'm sorry, but I don't have the patience to deal with someone who continues to assert their point without offering the documentation and evidence to back it up. This is particularly true when your earlier post indicates that you don't understand mpeg-2, and you come very close to saying what I said about mp3."

Regarding your comments about MP3, I said a whole lot more than what you said about MP3, and yet you still missed the point. I do, however, agree with the other comment above. So much so, that I won't even paraphrase it. I'm sorry, but I don't have the patience to deal with someone who continues to assert their point without offering the documentation and evidence to back it up. If you care to change your approach to this discussion and start make informed statements, factfind to source out your information, make a genuine effort to understand the points being made, and respond to posts on a point-by-point basis, I will be inclined to respond to any further posts you make. Otherwise, I lose nothing by discontinuing this conversation.

- Collapse -
how is the qualityof your camera?
Nov 13, 2005 1:17AM PST

how is the qualityof your camera?
how is Sony Vegas

- Collapse -
Quality of sound recording GZ-MC500
May 9, 2006 8:23PM PDT

I found your various reviews of the video quality of this machine very useful.

However, I wonder if someone could give me the benefit of their experience of the sound recordings. I want to use this camcorder to record role plays in a training room. Is the recording quality good enough to deal with subjects that are 9 feet/3 metres away? I see that this machine does not have an audio in......

- Collapse -
What you need to consider...
Oct 26, 2005 2:54AM PDT

So, there are three main choices available to you as far as camcorders go (discounting analog technologies, since they are antiquated): miniDV, DVD, or hard-drive/flash. There are pros and cons to each, but the relative impact of these pros and cons depends on the use you intend to get out of the camera.

MiniDV camcorders currently represent the largest segment of the camcorder world. In this regard, you will have a greater selection of products to choose from. DV is an easy video format to edit and most, if not all, video editors out there are capable of editing DV. Because DV is not heavily compressed, the video quality is very true to the image captured by the camera's sensor. Generally speaking, miniDV camcorders will yield the highest video quality. However, you are stuck with recording on tape, which is a pain in the butt. The tapes are only playable in your camcorder, and so don't lend themselves to easy viewing. If you want to archive your tapes to DVD, it will take many hours per tape to compress them to MPEG-2 format and then burn to DVD.

Bottom line: MiniDV camcorders have excellent video quality, and are a good buy if you plan on editing all of your video before burning to DVD.

DVD camcorders are still relatively new to market. As such, there are only a handful of brands to select from when purchasing a DVD camcorder. The video quality of the DVD based players is generally not as good as the top of the line miniDV camcorders, but is comparable to middle of the line miniDV camcorders (so you do pay a premium for the DVD recording). They also require expensive media (mini DVD-Rs, etc), and each DVD-R can only hold 20 minutes of DVD quality video. If you tend to do a lot of recording, this may prove to be awkward. Imagine having to change mini DVDs three times during the course of your child's birthday party! However, once you finalize the disc in the camera, the video is ready to be played in almost any DVD player. The video is stored on the mini DVDs in MPEG-2 format, which is highly compressed and thus hard to edit. There are only a handful of editors out there that are capable of using MPEG-2 as a video source.

Bottom line: DVD camcorders have good video quality, and are convenient for videographers who only record sporatically and do not wish to edit much of their video.

Hard-drive/flash based players represent the smallest and newest segment of the consumer camcorder product lineup. As such, there is very little selection at the moment. I'll focus on the hard-drive camcorders, since I own a JVC Everio GZ-MC50. These record in MPEG-2 format, similar to the DVD camcorders. Thus, the video is also harder to edit than DV video, and the selection of video editors capable of the task is less than that for DV video. The quality of the video is also slightly lower than that of miniDV, since the camera is recording in MPEG-2 realtime. Instead of encoding in a 2-pass method, such as used in DVD authoring software. The hard-drives hold a lot of video though, so you don't have worry about changing media midway through recording. You can also archive to DVD very quickly, since the video is already in MPEG-2 format.

Bottom line: Hard-drive camcorders have good video quality, and are a great buy if you do lots of recording, want to archive straight to DVD, and are not obsessed with editing all of the footage that you shoot.

NB: The resolution of the sensor really has an impact on the quality of the video with MPEG-2 encoding cameras, though, so if you are going to choose a DVD or hard-drive based camera, choose the higher resolution models (ie. GZ-MC50 instead of GZ-MC30 and GZ-MC20).

I found the capacity of the JVC GZ-MC50 camera, the convenience of quick archiving, and the ability to edit the video if and when I choose to do so, all compelling reasons for me to buy a hard-drive based camera. I've had the camera for a couple of months now, and I am very happy with it.

- Collapse -
I made the original post and I appreciate
Oct 27, 2005 12:44PM PDT

all of the information provide. The battle has been entertaining! I have learned a lot and I am leaning strongly torward the Hard drive system. I do plan of doing simple editing and the capacity and cost are huge factors in my choice. The price of the 30 gig capacity drive may be a few hundred more than a comparable mini-dvd camera, but I saw how much those mini dvd's cost. It would take no time to spend a few hundred on those. Especially for a parent record their child's every move. The rewritable dvds tend to lose quality after repeated plays I've heard, and I'm guessing the hard drive camera doesn't have that problem.

- Collapse -
My decision
Nov 1, 2005 6:45PM PST

1, I'll buy JVC MG70
2, DV maybe very better than MPEG-2, but I like MPEG-2 because it's easy to backup and I don't need to edit or I have no time to edit it. And its quality is ok to me.

I think there is only a little professional customer who is not like MPEG2.

Now the MG70 is expensive, I'm waiting its discount.

- Collapse -
What you need to consider...
Oct 28, 2005 2:53AM PDT

You did an execlent job on this post!!!!
The only thing I would add is the problems with DVD cameras. If you fill the DVD you may NOT be able to finalise it and make a coster. If you jar or shake the DVD camera while it is recording it MAY runin the recording and make a coster. John

- Collapse -
And further consider this...
Oct 28, 2005 3:08AM PDT

You can throw physics out the window in the argument to uphold MPEG recording vs. DV. Fist, all camcorder formats do compress somewhat, but MPEG hard-drive and DVD recording formats compress way more than DV. The result? Hugely degraded video quality. Kiddpeat is correct in his statement that in the process of uncompressing these formats for any kind of editing, there will be further degrading of the video that was just recorded. Further, if anyone thinks MP3 audio sounds just as good as .aiff or full-bandwith audio formats, they must be deaf, because MP3 is severely degraded. Same issue with MPEG recording. So, is it worth having a lower-quality video recording for sake of a bit of convenience? Only the end user can answer that.

- Collapse -
Why do people keep referring to physics?
Oct 28, 2005 4:33AM PDT

This is not a case study in physics. If anything, the subject at hand is mathematics.

It is true, MPEG-2 is more compressed than DV. It is also true that the video quality of MPEG-2 is less than that of DV (given camcorders that are equal in all other respects). However, I beg to differ on the "hugely" part of the "hugely degraded video quality" statement. The fact that Hollywood uses MPEG-2 to distribute movies (not DV) is a testament to two things. One, DV takes up too much room for a final distribution. And two, MPEG-2 displays very good picture quality given a good source. Note that I am not saying "perfect picture quality", nor am I saying "excellent picture quality", nor am I saying that MPEG-2 has better picture quality than DV. I am simply saying that the fact that MPEG-2 is the defacto standard of Hollywood (an industry that revolves around video), it cannot be as horrible as you say. Also, as I pointed out earlier in this discussion, the video industry has chosen to use MPEG-2 for HDV (and this is also being supported by Final Cut Pro and other professional editing apps). This further suggests that MPEG-2 cannot be that "horrible" a compression format, since professionals will be the ones using these cameras. Eventually consumers will too, but not at current prices.

Also, no one in this discussion has said anything about MP3 audio sounding as good as .aiff or full-bandwidth audio formats. We could get into the age old CD vs LP argument if you really want, but that was never the intent of the discussion. I can't emphasize enough that you need to read was it being written carefully, so as not to infer something that is unintended by the writer.

- Collapse -
Hollywood uses mpeg-2 because that's what they need to do
Oct 28, 2005 9:25AM PDT

to fit their material on a DVD. It is not a testament to the quality of mpeg-2. It is a testament to the inability to fit more data on a disk with current technology.

- Collapse -
Again, look up the HDV specification
Oct 31, 2005 4:38AM PST

Who do you think is behind the HDV specification, amateurs? They chose MPEG-2 compression for the HDV specification. You keep dancing around that one. I have noticed that you don't respond to any of my posts regarding that. Why? I do not argue that MPEG-2 is superior to DV given that all other factors are equal, but the trade offs must be compelling enough to motivate industry experts (unless you assert that the HDV consortium is populated with amateurs and dimwits) to choose it over some mutated form of DV. Don't let the name HDV fool you, it is based on MPEG-2. Look it up, and respond to this for once!

Regarding your assertion that Hollywood uses DVDs because that's what they have to do, I disagree. The technology sector develops technology based on demand. If the demand had existed for more space, they would have developed a medium that provided that space. The fact of the matter is that Hollywood distributed DVDs exceeded the resolution demands of SD television, even with MPEG-2 compression. That is why they chose the technology. Now that HD televisions are becoming more prevalent, they are investing the development of larger capacity DVDs (Blu-ray and HDVD) in order to deliver content at a higher resolution.

- Collapse -
mpeg-2 is used by HDV for many reasons. One is
Oct 31, 2005 7:40AM PST

compatibility with existing cameras. They didn't have to develop a whole new camera to add HDV. They fitted it on top of the existing cameras. How big is the mpeg-2 file coming from a Sony FZ camera? When you find the answer to that, it may ring a few bells. It's all about capabilities, costs, and a raft of other considerations.

Another reason, of course, is, as was the case with the DVD, they are doing what they have to do to fit the material onto the media. Will they stay with mpeg-2 when our equipment has far larger storage capacities? It's hard to say, but, if they do, they will probably be wishing they didn't have to.

How much HDV have you recorded and edited? What did you use to do it? Actually, I don't remember 'dancing around' the HDV question at all. Perhaps you can link to the post where you mentioned HDV and I 'danced around it'.