Problem capturing HDV footage

[Marcus Martell]

Hi guys i'm using a HDV hvrm15 to capture my footage, but often happens to me to have issues when i capture HD.When i capture SD everything is fine,but when i log to capture HD tapes it writes me"Device not Available".Even if i go to:Recconect current device nothing changes.Sometimes it works good,most of tomes don't!The hvr-m15 is connected to my external firewire HDisc.
Do you have any ideas?

[Steve Renouf]

Hi Marcus,

I'm not familiar with this machine but, when you say it is connected to the ext FW drive, I assume you mean via the PC!?! And that the software on the PC is capturing FROM the VTR TO the ext drive.

What software are you using to capture?

I take it the VTR is connected to the PC via FW and the PC is connected to the ext HDD via FW...

[Marcus Martell]

On my laptop there's just 1 firewire port.So i connect my lap to the external HD then the HD to the VTR.I think the problem is with hdv(not always but often),on the other side with sD footage everything works like a charm.

thx 4 everything Steve and Happy Easter

[Steve Renouf]

I think you may need to invest in an additional express card for your laptop so that you can FW IN from the VTR and FW OUT to the HDD. With the extra data throughput requirements of HD, I suspect you may be swamping the I/O with too much data trying to ust the same conduit for IN and OUT simultaneously. It might (just about) work for SD but with HD there is just too much data trying to do both directions down one line.

Daisy-chaining devices doesn't work too well in these situations.

[Steve Renouf]

Another thought - you could maybe try:

VTR -> (FW IN) -> Laptop -> (USB OUT) -> Ext HDD

although USB isn't really optimised for streaming video, it should work if the bitrate isn't too high.

[John Miller]

Camcorders (DV and HDV) are notorious for their refusal to behave correctly on FireWire buses. I was forever having issues until I switched to using USB2.0 drives and leaving my FireWire for the camcorders. All of my external drives that have FireWire also have USB2.0 (but not necessarily the other way around). Also, the FireWire bus can only operate at a fixed speed so if your camcorder uses 100Mps then your hard drive(s) will have to switch to the same speed.

[Edward Troxel]

HDV is the same bitrate as DV. So if DV works in that configuration, I would think HDV would as well.

I've captured tons of DV footage via:

Computer <-> firewire <-> hard drive <-> firewire <-> deck

[Seth Bloombaum]

I can confirm what Steve & John suggested:
The data formats a camcorder/deck uses in firewire transfer are different than the hard drive. Sometimes, having the devices on the same bus works, sometimes it doesn't, it remains a mystery why Edward's and others' configs seem to work all the time.

As suggested, in the case of a laptop you may go to USB for the drive, or, add a PC-card or ExpressCard firewire card. This cleans up the problem consistently.

[Marcus Martell]

My config is the same that ED has.
Sometimes it works, but when it happens that i have to unplug my pc from the hard disc and the deck this issue happens!At least are 2 years i'm not using USB ports to edit the captured clips to avoid the bottleneck.
So ypur suggestions will make me change my mind?

[Steve Renouf]

Originally Posted by Marcus Martell

My config is the same that ED has.
Sometimes it works, but when it happens that i have to unplug my pc from the hard disc and the deck this issue happens!At least are 2 years i'm not using USB ports to edit the captured clips to avoid the bottleneck.
So ypur suggestions will make me change my mind?

USB's theorical maximum data throughtput speed is 480 Mb/s and IEE1394's is 400Mb/s so it's not really a bottle-neck in that sense. However, when dealing with video capture/playback it's the "sustainable continuous streaming data rate" that is the important factor - and IEE1934 wins that battle hands down. Part of the reason for this is that USB relies to a great extent on the CPU power of the host system, whereas Firewire doesn't need a host - it's all done by the interface hardware and was specifically designed for audio/video for that reason - whereas USB is intended for normal data where fluctuation in data rate doesn't matter.

Usually, in this context, the limiting factor is the "sustainable continuous streaming data rate" of the drive itself - which is considerably slower than the actual interface - typically around 35Mb/s (the important measure for our purposes being the "sustainable continuous streaming data rate"). Sometimes, the drive will have a much faster "maximum burst data rate" but that's no good for video capture etc, which requires a continuous stream at a continuous data rate. That's the reason most "Pros" will use RAID arrays (where 2 or more drives are parallelled together in a RAID0 array to increase the handleable data rate - especially when capturing to an intermediate format.

Anyway, getting back to the plot, there is a lot more going on with HDV than DV, due to the high compression of the mpg long GOP format of HDV compared to Standard DV - so when using an intermediate codec (such as cineform) there is a lot of extra work being done to decompress the data and a much higher rate data stream.

However, if you're capturing in native HDV (mpg2-TS) the data rate for capture (as Edward pointed out) isn't the issue. I suspect the issue lies more in the hardware implementation of the actual devices you're using (in daisy-chained mode). It's fine for daisychaining several devices where a continuous stream isn't critical but I would personally get a seperate IEE1934 card and connect one of the devices to that rather than trying to pull data from the VTR to the laptop interface then back to the VTR interface through the same "pipe" then onto the HDD.

[Seth Bloombaum]

Originally Posted by Steve Renouf

...Usually, in this context, the limiting factor is the "sustainable continuous streaming data rate" of the drive itself - which is considerably slower than the actual interface - typically around 35Mb/s (the important measure for our purposes being the "sustainable continuous streaming data rate"). Sometimes, the drive will have a much faster "maximum burst data rate" but that's no good for video capture etc, which requires a continuous stream at a continuous data rate. That's the reason most "Pros" will use RAID arrays (where 2 or more drives are parallelled together in a RAID0 array to increase the handleable data rate - especially when capturing to an intermediate format...

Steve is quite right. To add a little - Both DV and HDV capture call for sustained transfer rates of 25Mbps. In practice, many editors (including me) have invested in external USB drives with their own power supplies, easily capturing with no dropped frames, and sustaining "best/full" previews of a single stream at full framerate.

In practice, there's been no perceivable preview difference in editing a single stream between my external USB drives and my internal Raid-0. The raid is a good one, not the OS drive, it is hardware controlled from an embedded controller on the the motherboard, SATA.

[Jason Robinson]

Originally Posted by Marcus Martell

Hi guys i'm using a HDV hvrm15 to capture my footage, but often happens to me to have issues when i capture HD.When i capture SD everything is fine,but when i log to capture HD tapes it writes me"Device not Available".Even if i go to:Recconect current device nothing changes.Sometimes it works good,most of tomes don't!The hvr-m15 is connected to my external firewire HDisc.
Do you have any ideas?

I have bypassed this issue by simply never logging footage to an external HD. I always record to the internal HD and then move it to an external HD when logging is done (or when I run out of space).

[Marcus Martell]

Unf my hard disc is just 120 gb....I own a laptop so i have space restrictions....

[Marcus Martell]

What about if i buy a pcmcia card with 2 or more firewire ports?
My pconly has 1 so i was thinking about it?
Suggestions?

thx

[John Miller]

I have three different PCMCIA FireWire cards for use with my laptops. One is an Adaptec with three 6-pin ports. The other two are Pyro and use a dongle to give one 6-pin and one 4-pin port. The advantage of the Pyro ones is that they are completely flat and so you can put two in at a time (unless you have just a single PCMCIA slot which is becoming more common unfortunately). I can connect up to five at a time (3 via the Adaptec + 2 via one of the Pyros) + another with the built-in FireWire. Not that I need six very often on a laptop!

As far as drives and cams go, adding a PCMCIA card will allow you to run your FireWire hard drives on one interface and your cam(s) on the other. Since most built-in FireWire interfaces on laptops are 4-pin (like the cams) and the PCMCIA ones are powered 6-pin (like the hard drives), it would probably be easiest to plug the drives into the PCMCIA card.