file size of 60 min HDV and MPEG" HD

[Rajuk]

HIya

can anybody tell me how much hard drive space 60mins of HDV takes?

IS iit the same as DV ? is in roughly 25gb for every 60min? Or is double etc?


ALso if i have a MPEG HD file with 1080 lines how much would one hour be in Gb?

Actually what i reall want to know how many minutes can i fit onto a standard dual dvd ?

I was unsure as with normal DVD the time can vary depending on the encoding rate etc

thanks

[mooblie]

HDV takes about 13GB/hr, as does DV. (Not sure where you got the 25GB from?)

You can't really put encoded HD on a standard DVD.

(Well you CAN, and I think it's about 15 minutes on a 4.7GB DVD, but it's not a standard, and not many - or any? - players will play it.)

Rajuk, HDV is a different ball game from DV - you need to be talking about HD-DVD or Blu-Ray discs, neither of which has reached the mainstream yet. Burners, blanks, authoring software, etc. are all in the very early phases of their life at present, being expensive, in short supply, buggy, or all three. To say nothing of set-top HD players of course.

Probably most advanced in their product life cycle are paradoxically the two opposite ends of the chain - camcorders and HD-ready screens. The bits of the chain in between (not forgetting your NLE, of course) are coming up behind.

And the duration you can fit on a HD-DVD or BluRay BD will depend on the encoding rate, like DV. But it's not MPEG-2, it's likely to be H.264.

(All open to shooting down in flames, from one more versed in this than I.)

[Ron Spicer]

That's roughly what the manual for DVD StudioPro 4 says Mooblie !

[Rajuk]

hiya many thanks

i must have got mixed up

I m thinking of buying the hc3 sony hd cam instead of the sr1e as it has no editing support.

i was just thinking of storage and the possibilty of storing material on to disc once converted--but thanks for the advice

[Alan Roberts]

HDV and DV are both 25Mb/s (actually there's a variant of HDV that's a bit less, but let's ignore that for now). That's the transport stream that's recorded on tape and comes down the firewire cable. That's 13GB/hour.

But, HDV is MPEG2, and so most of the editors for it offer to transcode it into an intra-frame format that is inevitably more GB/hour. Canopus' version is about 60GB/hour.

Incidentally, beware of abbreviations, HDCAM is the professional intra-frame format at 144Mb/s, and the HC3 is an HDV camcorder, not the same by at least about 2 orders of magnitude in price.

[George Rankine]

Alan, I'm a bit confused now (not difficult..) Do I understand that the firewire signal is uncompressed (if that is the data that is on the tape) and if so, then how does the HDMI sognal differ?- I appreciate the copy protection aspect, but is that all?
George

[Alan Roberts]

Firewire is essentially a transfer format for video, as far as we're concerned. To be more accurate, firewire is the trade name for thge standard IEEE1394 data protocol which was introduced as a small-office networking system, and that's how we used it for moving data around. Anyway.....

The firewire DV signal is in the same form as the data on the tape. It's compressed 5:1 down to 25Mb/s (intra-frame only, so each frame stands entirely alone) for recording, and travels over firewire in that compressed form. It is decompressed only for viewing or processing during editing.

The firewire HDV signal is in the same form as the data on the tape. It's compressed about 25:1 down to 25Mb/s (MPEG2, 12-frame GoP for 1080/50Hz or 720/50 systems, 15-frame GoP for 1080/60Hz or 720/60 systems, 6-frame GoP for 720/25 or /30 systems) for recording, and travels over firewire in that compressed form. It is deompressed for viewing and any processing other than cut editing, and even then may have to be decompressed if the GoP structure becomes unstable.

HDMI is completely different. It's the second generation of data connection for delivery pictures to displays. The first was DVI, which is essentially a digital version of VGA. Compression is really not a part of this connection at all, as far as I'm aware. DVI justy shifts the video as digital signals, but HDMI has another layer of protocol on top which supports encrypts the signals to prevent copying.

Does that help?

[mdiver]

hiya many thanks
i was just thinking of storage and the possibilty of storing material on to disc once converted--but thanks for the advice

So are you basicaly talking about "backup" of the data for later use?

I don't think DVD's store enough to make them useful. Hard drives are very cheap for data storage now days, price per Gb. Or just leave the video on mini-DV.

[George Rankine]

Thanks, as usual Alan very comprehensive.So do I understand correctly that we will in future still use the firewire for editing etc or do you think eventually we will move to HDMI sockets in computers as the new cameras come out with HDMI sockets eg the new sony v1?

George

[steve]

George,

The role for the new HDMI 'capture' cards/adaptors is really limited to just live capture to disc. They will allow the uncompressed signals to be recorded before they are squeezed into a 25Mb/s stream. At several hundred megabits per second, its only currently practical on large fast hard drives. i.e. a 2.5 inch laptop drive would fill up in a few minutes even if it could handle the data rate!
Once the video goes onto tape there is no point using anything other than firewire to transfer to the editing platform as Alan has commented, the compression is the same.
So I imagine that firewire will be the preferred method over HDMI, (and HDSDI on some of the new Canon HDV models) for most people for some time.

Steve

[Alan Roberts]

Spot on, George. Firewire is a great way to move data about, and is very well established, so will survive; but the connectors are small, fiddly and vulnerable, and cannot handle uncompressed HDTV in real-time. HDMI is the standard for getting pictures (and sound) to the display, so it'll happen in computers and tv sets; it's already the standard input for HDTV into HD displays and is tidy and robust.

[George Rankine]

Thanks Steve and Alan for clearing that up, my apologies for not replying sooner but was en route Heathrow/Edinburgh.

George

[George Rankine]

Have been having a further thought on the above points overnight and I have another problem. If as Steve says, the HDMI output is prior to creating the 25Mb stream (which presumably has to happen prior to recording on tape,) then surely this will only function if the output is taken straight to eg hard drive (and therefore stored that way), and not on to tape, and therefore will only just be of use for feeding a tv if the output from the hard drive is taken directly? Therefore it (the HDMI output) will not function if eg one replays a tape in the camera as the data has alredy been converted to25 Mb? Or is it back converted, abd if so will it be any better than The component o/p I alredy use to monitor the output on my plasma? mmmm.

George

[George Rankine]

PS if I don't answer any replies, apologies in advance as I'm off to darkest Spain for 11 days..

[steve]

George,

The proprietary cards being offered e.g. the Blackmagic Intensity, that take an HDMI stream, convert it to something that can be stored at that datarate. I assume that the storage would have to be a fairly fast raid array, as the datarate is in excess of 500Mb/s uncompressed. Blackmagic say that the Intensity can also offer other codecs with lighter compression, specifically, DV100 is mentioned (DVC100?) as well as a JPEG based scheme of their own. (Surely JPEG will defeat many of the advantages of using HDMI?)
They also talk about 1920 sample resolution as opposed to 1440 of HDV. The problem is that commercial HDV cameras are engineered from the lens to the compressor to optimise a 1440 sample signal. Using an HC3E as a source, as suggested on their site, will surely show all the limitations of the lens, the CMOS array, the Beyer filter etc. - only the MPEG compression will be bypassed.
The Intensity card does have an HDMI output for feeding NLE output to a TV/Monitor, but all of this is only practical with mains powered PCs and raid arrays, hardly compatible with an HC3E.
I find that the component output is not very good on any of the Sony HDV cameras, - the gamma seems poor and the edges ring much more than viewing a firewire or HDMI signal of the same footage.

Steve

[George Rankine]

Steve, but that's my point- an HDTV doesn't have a firewire link and we've only just got cameras with HDMI out- so how do you connect them to a monitor other than with component?

Sorry see above, may not be able to answer for a week!!

Thanks, George

[steve]

George,

At the moment the only choice for those cameras without is by Component, or use a PC and route the VGA (or DVI) through.

Steve