Every bit of video you ever shot with your MVX35i camera has been compressed. DV is a compressed format. The compression is 5:1. Even when you render out to DV AVI that is still a compressed format.

Think of how mp3s changed the world of music. mpeg-1 was not good enough compression to do it. mpeg-2 was not good enough compression to do it. Mpeg-3 was good enough to deliver quality sound at bitrates under 200K. Well mp3s is fairly old technology. As computers get faster, higher compression schemes become available because modern cpus are able to decode them on the fly. mp4 is better compression than mp3 and that's been around a few years. HDV is mpeg-2 based, they just use an incredibly high bitrate. AVCHD is the latest compression scheme to come out. It's about a year and a half old. It was developed specifically with HD in mind. AVCHD would have been completely unworkable say 5 years ago. It does a ton of math to do the compression and requires a lot of CPU horsepower to do the math to decode the compression. If the CPU can't keep up with the decoding, the file can't play continuously.

So yes, there are issues with compression with AVCHD, but they are not yesterday's issues with compression.

How does HDD rate to TAPE when recording footage, compression, bitrate, etc..

Bit

Why do peopel state that MPEG2 is a bad compression for editing and prefer tape.

So, I am still confused - if picture quality is paramount, why then do people prefer tapes when they are compressed at MPEG2 quality?

Bit

How does HDD rate to TAPE when recording footage, compression, bitrate, etc..

This has been asked and answered: there is no difference: The codec determines the compression; the recording media (tape, memory stick, HDD) just simply stores the bits and later plays them back. The only thing the media affects is the speed with which the resulting data can be copied, with memory stick and HDD having the advantage that the data can be copied to another location (such as the editing drive on your computer) at a speed faster than real time. It also can have additional important characteristics, such as random access, so you can get to a particular scene instantly, something tape doesn't do at all.

That's not the right question to ask. HDD and Tape are simply media. You can record HDV to a hard drive or to tape. You're asking about comparisons between codecs/video formats. Tape and hard drive, means you have a different editing workflow, but the format is more a determining factor.


Given your needs in your other post, go with HDV tape based cameras, either the Canon HV20 or the Sony HDR-HC7. Those are the most bang for the buck. Search this board and you'll see a lot of info. The general consent is the Canon is a slighter better picture and the Sony is better built.

Same as with flash memory, the storage medium doesn't determine the bitrate of the movie as such. Everything I wrote about flash is true for HDD at this point in time. In theory faster media will allow higher bitrates but at this time space is more of a problem than bandwidth.

Why do peopel state that MPEG2 is a bad compression for editing and prefer tape.

Tape is MPEG-2 for HDV. It might also be AVC, the storage medium doesn't as such determine what codec is used or what bitrate is used (sorta, tape limits bitrate somewhat but not enough to matter at this point in time for consumer stuff).

Forget about PQ, the PQ will be similar on all the HDV/AVCHD camcorders. Don't worry about it. It doesn't matter. Two things are going to be relevant for you:

1/ Editability - HDV is currently easier to edit than AVC. This is related to compression etc, but there is no reason to know the technical details.
2/ Space - can you shoot all the footage you need on the medium you chose.

It's that simple. If you can survive with the limitations of consumer HDD or Flash camcorders as outlined above, go for it. If you can't, go with tape. If you have a less than super-fast PC, I would probably also go with HDV since it will be easier for you to edit.

Perhaps there is another point which everyone has been too polite to mention: on various websites a lot of technically ignorant opinions are strongly expressed about the deficiencies of HDV, codecs, and recording media (and cameras). This isn't limited to non-professionals, and too many people make statements purporting to be facts but actually are opinions and often of the "somebody in a bar told me" variety. So the difficulty is in being able to sort the wheat from the chaff. On this site, generally, you can rely on the advice given.
To summarise the various inputs above:

1) HDV provides high quality images, irrespective of recording medium;
2) the recording medium doesn't affect editing (ignoring certain conveniences);
3) computing power and NLE does affect ease of editing
4) tape is cheaper than flash cards and more readily available;
5) cameras recording only to flash memory may require additional logistical support that may be inconvenient;
6) switchable 50 Hz / 60 Hz capabilities may be important (often not available at the consumer end).

Apologies for other points not remembered!

good points serena....

however, as a freelancer who shoots for a variety of clients, incl. our own abc, there's no way i can, or would shoot tapeless. what am i going to do, send expensive cards to my clients in the hope they'll send them back?

from my pov, tape will be around for a long time yet - not only for the above reason, but most of the doco's i work on are shot over very long periods, 2+ years, and to have hd storage sitting around that long is both costly, and can be dangerous in as much as i've had hd's seize up on me after months of storage....

okay, not as fast as cards, but certainly a whole damn site more reliable....

leslie

Why do people state that MPEG2 is a bad compression for editing and prefer tape.

This was the received wisdom when MPEG-2 meant DVD quality, When HDV came out and changed how MPEG-2 was used, some folks never caught on to that. The difference is the bitrate.

I think the folks who disparage mpeg-2 are confusing the mpeg-2 that is used to render to DVD and how mpeg-2 is used in HDV. The difference is the DVD spec has a max bitrate for video of around 8Mpbs and HDV has a bitrate of 25Mbps. All those extra bits really help. There is much less picture degradation in editing HDV.

Agree that the logistics of flash card recording are in early days and I think that workflows are still quite individual. Certainly I wouldn't hand over an SxS card, so the question of "what do I give the client" is important. Generally my work doesn't involve shoot only, so my practice is to download immediately to laptop external HDD (those little WD things of 80 to 120 GB), and from there to data DVD for storage. Haven't gone BluRay, yet. I think optical storage is better than tape, but that's only opinion and now, of course, I don't originate on tape!

I can testify that DVCam tapes here have lasted at least seven years, and we definitely have to go back to that far for things at times. (DVCam writes the same data over more tape, like writing with a fat pencil, and this helps make the formata little more robust.)

I was one of the ones making a comment about compression schemes based on mpeg2 (like HDV and XDCam). Basically I was repeating what I have been told by the people making the Galapagos doc. While I think I described them as my friends, they also happen to sign my paycheck. The person who actually does the shooting and editing holds some opinions that are are rooted in many years of experience, but they are admittedly skewed to received wisdom.

The knocks on long GOP and other MPEG-like schemes are that (supposedly) they degrade when there's a lot of motion in the shot, and that the bitrate is just too anemic for HD. These have been the two reasons why HDV and DVCam have not even been open for discussion here.
And this is why they chose DVCProHD at 100 Mbps (on tape).

Do I totally believe this? Not entirely. I don't think that the bitrate is quite the issue it's cracked up to be, and I don't really know about the motion artifacts. However, this also gets wrapped up in how you work. If you are rendering upwards to less compressed formats as you work then I think the issue is not nearly as bad, in the same way that you can originate in DV but you shouldn't finish in DV.

The idea that Panasonic is trying to get away from paying licensing royalties to Sony for tape transport technology was just recently dropped on me. Don't know if it's true but interesting in light of their posh to solid state.

Rob Mack

I must admit I'd rather record on film. When considering moving to video I was rather aghast at the idea of long GOPs and 25x compression and certainly expecting all manner of artifacts. So I understand why people think it won't work. It's interesting to read these discussions on CML and the counters Adam Wilt puts forward. Generally these are in the nature of "I've tested this thoroughly and you're wrong". Would I go back to film? Of course, given the budget. But the EX1 is producing HD images (1920 x 1080P, 35 Mb/s) that have the major characteristics I associate with film and very definitely much cheaper, more flexible, and very nice to use.
Galapagos? You go with the stuff you know will meet the need. Not stuff that might do it, or even might do it better, but which doesn't have your confidence.


EDIT: I think the answer for EX users who have to give the client the day's shooting is the USB flash memory; 8 Gb are cheap and you add that to the cost of the job. Or my preferred WD USB 80Gb drives which are small, slim, and are bought here for under $100; in the US you probably get them given with your change.

Oh yes, if you go somewhere to shoot for a month where you can't get replacements, you go for tried and true gear. We've actually been a bit dismayed at Panasonic's retreat from tape.

Rob Mack

1) Me, to SxS
2) Absolutely
3) Loss???? Digital is better than analog stretchy degrading tape.
4) No. From HDV to HD (mpeg4).

I've lost more stuff from tape than HDD or flash. Some people like to buy cheap MiniDV tapes and I've had several of them get shredded, nasty feeling when the VCR makes the wrong kind of noises.
What's odd is everyone freaks over the reliablility of video on flash or HDD and yet how many are still recording audio to tape. My DAT drive is only used for archival retrieval, I only record something to DAT or R2R to check that the units are still working.
Reality is apart from maybe DB, tape transports can screw up very easily, especially in hostile environments.

Bob.

Thanks to all those who replied - you guys are swell and really value your inputs!

Key points - Bitrate and different levels of understandings of MPEG2.

Farss, do u use flash or HDD and what model vid cam?


Bit

Terje,

I reply to your earlier post 4/10/2008 12:14:45 AM :

Wouldnt it be great to have 2 x 120GB HDD (1 spare) - on a trip.

This woudl certianly minimise carrying stuff around - woudl it not?

Bit

Flash, SxS, EX1.

Perhaps one different wya of looking at this is as the difference between a data-centric and video-centric workflow.

Videotape doesn't have a whole lot of error correction built in. It can be difficult to clone, so dubs loose quality. DV can be cloned 100%, HDV can also, with the right VCRs. Other formats are not so easy to impossible to clone.

Datatapes and other data storage media can have a very large amount of error correction and is very easy to clone. The copies are bit accurate and can be verified as such.

No matter what you acquire with be it DV tape or 35mm film the human factor cannot be ignored. Camera neg has been 'lost', tapes overwritten and/or lost. We pretty regularly get kit back with tapes left in it. What I do like about tapeless acquisition is it's datacentric and therefore easy to backup. My shoot today will be backed up in three places tonight. By the morning it could be backed up on another continent if it was worth the cost of the bandwidth.

I personally think tape will be with us for a very, very long time. But it'll be storing video as data. Now to save up the dollars for a LTO4 tape drive :)

Bob.

Does anyone know if the Sony SR12 can shoot HDV as well as ADVCD?

Thnaks Farss,

Your thougths on using flash or HDD on the camcorders (such as Sony SR12)?

Bit

The stuff in thi slink is what confuses me...and your psots up here - seem a bit confilcting... :-(

http://au.answers.yahoo.com/answers2/frontend.php/question?qid=20080220225914AAhkHzR

"Comparing a miniDV tape camcorder that recorders to DV or HDV against a hard drive based camcorder that compresses into MPEG2 or AVCHD is not really a fair fight. DV and HDV wins. The video quality, ease of use, shelf life, working with editors and archival are why they use them. Compression = lost data = reduced video quality. DV and HDV compress a lot less than the other storage methods which translates into DV and HDV providing best quality."

Thoughts?


Bit