Question on USB2.0 vs Firewire 400/800mbps

[jcikal]

I have a sony camcorder which has support for firewire1394. Now, I know there's a 1394b which goes up to 800mbps vs the 1394 which is 400mbps. Question is if I purchase a 1394b card and connect it to my camcorder, will it give me the 800mbps of the card or will it give me 400mbps. Is the amount of mbps ruled by the device or by the capture card? Thanks for any info.

[RMaddog]

Transfer rates are ruled by the slowest device. That said if your device will support to new transfer rate then it shoul d give the 800 Mbps. However, since more than likely it does not it will only do the 400 Mbps

[redwudz]

Good question. AFAIK, both devices(Camera or HD and the 1394 card) would have to 1394b to achieve the 800Mbps transfer. 1394b is fairly new, and I only know of some external HD boxes that use it. I don't think there are any cameras yet.

BTW, transfer from your camera will probably never strain the 400Mbps rate of the 1394a standard. The transfer can only occur as fast as the tape can output the DV signal and that's a lot slower.

Also since you mention USB; On video cameras that is generally only used for still image transfer.

[jcikal]

Ok, here's an interesting question, if I purchase a camcorder that supports 1394b at 800Mbps, and then put my DV tape which I recorded in my older camcorder which supports 1394a at 400Mbs into the new camcorder, will the tape transfer at 800Mbps or will it revert to 400Mbsp? I don't know if that kind of information is coded into the tape or not, so that when you record it in a 400Mbps camcorder even if you put the tape in a 800Mbps camcorder, it will revert back to 400Mbps. I hope someone can understand my question. Again, any info. will be greatly appreciated.

[dipstick]

No matter what you have, the camcorder will only export in real-time. That means a transfer rate of only 25 MBs(mini-dv) or 50 MBs for DVC-Pro, well below the limit of even 1394a @ 400 MBs. The only benefit of 1394b that I can see, is if it's used for external HDD or Burner. For DV, it's over kill.

[redwudz]

Just speculation here, but there would have to some changes in the tape and the camcorders to send the data faster. Video tape is an analog media, even though it might contain digital information. It has to start at the beginning and go to the end at the speed of the tape transport. It would be nice to 'Fast forward' it to transfer, but I don't think the video head and transport could keep up.

Maybe if the tape were replaced with a solid state device, such as a very large memory module, the speed could be the maximum of the interface, including 1394b. The cost is prohibitive at present, but I'm sure some people are working on it.

A camcorder using a DVD or similar to record on is another way it can be done. I don't know what their transfer rate is, but it should be higher.

[jcikal]

No matter what you have, the camcorder will only export in real-time. That means a transfer rate of only 25 MBs(mini-dv) or 50 MBs for DVC-Pro, well below the limit of even 1394a @ 400 MBs

Does that mean that the maximum transfer speed of a Mini Dv camcorder (consumer or professional) is only a measly 25Mbs???

So even the cheapest of the cheapest 1394a @400Mbs cards is more than capable of giving me the perfect video quality from the Mini DV Camcorder? Am I right in assuming this? Thanks for any info.

[SLK001]

Real time is 25Mbps - that's how fast data is recorded (it can't send data that it hasn't yet recorded). Data transfers can be much faster - as fast as the tape can be streamed. Just remember that a DVD at max video rate is only 9.8Mbps, but that data is compressed.

[junkmalle]

Does that mean that the maximum transfer speed of a Mini Dv camcorder (consumer or professional) is only a measly 25Mbs???

Yes.

So even the cheapest of the cheapest 1394a @400Mbs cards is more than capable of giving me the perfect video quality from the Mini DV Camcorder? Am I right in assuming this?

Yes.

[Zen of Encoding]

Real time is 25Mbps - that's how fast data is recorded (it can't send data that it hasn't yet recorded). Data transfers can be much faster - as fast as the tape can be streamed. Just remember that a DVD at max video rate is only 9.8Mbps, but that data is compressed.

I'm starting to wonder if *anyone* involved in this thread has actually
performed the task of capturing video from a camcorder across a 1394a
firewire connection.

Full resolution 720x480 NTSC mini-DV video is transferred from a
camcorder to a computer hard drive, which creates .AVI files, at exactly
3.6 Mb per second.

If you don't believe me, try it. Capture 1 minute of video, then divide the
file size by 60.

If one wishes to afterward transcode the .AVI capture files into
MPEG2 files for DVD player use, one can select from a wide range of data
rates.

[junkmalle]

Full resolution 720x480 NTSC mini-DV video is transferred from a
camcorder to a computer hard drive, which creates .AVI files, at exactly
3.6 Mb per second.

No, it's 3.6 MB/s. Which is very roughly 25 Mb/s, the numbers others have referenced here.

For anyone who's confused, MB is Mega Bytes per second, Mb is Mega bits per second. There are 8 bits in a byte. So 1 MB = 8 Mb.

USB and Firewire usually state their speed in mega bits per second. Probably because the bigger numbers sound faster.

Hard drives usually specify transfer rates in megabytes per second. Mostly due to tradition.

[jcikal]

The confusion (if we can call it that) with Mbps and MBps is kind of like when ISPs advertise their DSL speeds. They list them as bits instead of bytes. Somehow advertising that your ISP provides 3 million bits sounds like you'll be going at warp speed, when in real life, you'll be going at roughly 300 bytes per second.

Continuing with the debate however, I guess if I go with a $20 or so 1394a card I should be able to capture exactly the resolution and speed that the camcorder recorded (Mini DV at 1080) right?

[junkmalle]

if I go with a $20 or so 1394a card I should be able to capture exactly the resolution and speed that the camcorder recorded (Mini DV at 1080) right?

1080? No. DV is 720x480 29.97 fps NTSC, or 720x576 25 fps PAL.

[jcikal]

Oops my bad. I meant 1080 pixels (that's how Sony states it so I got acustomed to stating that way). Sooo here's the same question (edited of course)

if I go with a $20 or so 1394a card I should be able to capture exactly the resolution and speed that the camcorder recorded (Mini DV resolution) right?

[dipstick]

Yes.

Any cheap 1394 card will be all you need. I bought my 1394 card 4 years ago for $25, it even came with Video Studio 6. It's still going strong with countless DV transfers from and to DV-Cam. As stated earlier, all Mini-DV is 25 Mbs. DVC-Pro is 50 Mbs. Hardly able to tax any 1394 with 400 Mbs transfer rate.

[Zen of Encoding]

DV is 720x480 59.94 fps NTSC

I'm sure that the above was just a typo, because NTSC video is actually
presented at a rate of 29.97 frames per second.

Or... are you now going to claim that your abbreviation was supposed to
stand for "fields per second", which would also be technically correct.
But, then how would you explain your using the same abbreviation for
the correct PAL frame rate, at 25 frames per second, not 25 fields per
second?

[MOVIEGEEK]

To clarify:
400Mbps=50MB/s
480Mbps=60MB/s
800Mbps=100MB/s

There are 8 bits to one byte.
As was mentioned earlier 1394b will be targeted for external HDD's.

[SLK001]

To clarify:
400Mbps=50MB/s
480Mbps=60MB/s
800Mbps=100MB/s

There are 8 bits to one byte.

Correct, but in serial transmissions, there are start bits and parity bits. So, a good rule-of-thumb is that a minimum of 10bits is sent for one byte.

However, I do NOT know what transmission protocal these units use.

[edDV]

To clarify:
400Mbps=50MB/s
480Mbps=60MB/s
800Mbps=100MB/s

There are 8 bits to one byte.

Correct, but in serial transmissions, there are start bits and parity bits. So, a good rule-of-thumb is that a minimum of 10bits is sent for one byte.

However, I do NOT know what transmission protocal these units use.

Not to confuse things more but DV is close to 36 Mb/s as sent over IEEE-1394. Of that 25Mb/s gets stored as video, audio and metadata add another ~5Mb/s for a total to disk of ~30Mb/s.

[junkmalle]

DV is 720x480 59.94 fps NTSC

I'm sure that the above was just a typo, because NTSC video is actually
presented at a rate of 29.97 frames per second.

Or... are you now going to claim that your abbreviation was supposed to
stand for "fields per second", which would also be technically correct.
But, then how would you explain your using the same abbreviation for
the correct PAL frame rate, at 25 frames per second, not 25 fields per
second?

Sorry, I originally was going to give fields per second but deciced to go with frames per second instead and forgot to change the value. Indeed NTSC is 29.97 frames per second. I corrected the original message.

[junkmalle]

Oops my bad. I meant 1080 pixels (that's how Sony states it so I got acustomed to stating that way). Sooo here's the same question (edited of course)

if I go with a $20 or so 1394a card I should be able to capture exactly the resolution and speed that the camcorder recorded (Mini DV resolution) right?

Are you talking about a HiDef DV camcorder like the Sony HDR-FX1? That may change the issue. I know it saves HiDef video in MPEG format on the same DV tapes. I suspect it doesn't require a higher transfer bandwidth but I don't know for sure.

[edDV]

Oops my bad. I meant 1080 pixels (that's how Sony states it so I got acustomed to stating that way). Sooo here's the same question (edited of course)

if I go with a $20 or so 1394a card I should be able to capture exactly the resolution and speed that the camcorder recorded (Mini DV resolution) right?

Are you talking about a HiDef DV camcorder like the Sony HDR-FX1? That may change the issue. I know it saves HiDef video in MPEG format on the same DV tapes. I suspect it doesn't require a higher transfer bandwidth but I don't know for sure.

From what I understand, HDV records a 720p MPeg TS stream at 19 Mbps and 1080i at 25Mbps but both within the DV specification so that it looks like DV to IEEE-1394,etc.

I may not have that right but the idea is to emulate DV.

[MpegEncoder]

Real time is 25Mbps - that's how fast data is recorded (it can't send data that it hasn't yet recorded). Data transfers can be much faster - as fast as the tape can be streamed. Just remember that a DVD at max video rate is only 9.8Mbps, but that data is compressed.

DV is also compressed, the ratio is 5:1

DVD is compressed more.

[edDV]

Real time is 25Mbps - that's how fast data is recorded (it can't send data that it hasn't yet recorded). Data transfers can be much faster - as fast as the tape can be streamed. Just remember that a DVD at max video rate is only 9.8Mbps, but that data is compressed.

DV is also compressed, the ratio is 5:1

DVD is compressed more.

DV stream data transfer from the camcorder is a fixed rate whether off tape, direct from the camera (live) or from analog pass-thru. With consumer level equipment, you can't speed it up.

If you record the stream into a DV-AVI file at the computer, then that file can be transferred under control of the OS at any normal PCI bus or network speeds including firewire to an external HDD or over a network. If the IEEE-1394 adapter is bound into the network, then the file can be transferred up to the full 400/800 Mb/s rates to another network node..

The camcorder is not networkable. It can only send or receive a DV stream.

[Zen of Encoding]

DV is also compressed, the ratio is 5:1

I've seen this 5 to 1 compression figure quoted before, interesting......

If I shot some video on a good 3-chip DV camcorder, perhaps a unit like
a Sony VX-2100, how could I export the video from the camera to capture
the completely uncompressed video you are referring to? The only other
option is the S-video connector.

Does this mean that the analog S-video connector has a higher data
band-width than the 1394a output of a DV camcorder, with regard to
video previously recorded to tape? Or.... is the video recorded to tape
at the 5:1 compression ratio. It would seem silly to have an
uncompressed video stream coming from the CCD chips without any
method of exporting it before it is compressed.

[junkmalle]

DV is also compressed, the ratio is 5:1

I've seen this 5 to 1 compression figure quoted before, interesting......

If I shot some video on a good 3-chip DV camcorder, perhaps a unit like
a Sony VX-2100, how could I export the video from the camera to capture
the completely uncompressed video you are referring to? The only other
option is the S-video connector.

Does this mean that the analog S-video connector has a higher data
band-width than the 1394a output of a DV camcorder, with regard to
video previously recorded to tape? Or.... is the video recorded to tape
at the 5:1 compression ratio. It would seem silly to have an
uncompressed video stream coming from the CCD chips without any
method of exporting it before it is compressed.

Here's how the 5:1 compression figure is calculated. DV uses 4:1:1 color subsampling in a YUV colorspace. This means 1.5 bytes is used for each pixel (on average). So with a 720x480 frame size, 30 frames per second you get 720 * 480 * 30 * 1.5 = 15,552,000 bytes per second. DV is about 3,600,000 bytes per second -- so you can see that's about a 5:1 compression. If your 3 CCD camcorder collects a full 3 bytes per pixel (RGB or YUV) then the compression is 10:1.

This compressed DV is what's saved on the tape. In theory it would be possible to send the full uncompressed data right from the CCD to the computer with a live picture. I'm not aware of any camcorders that have this ability.

[Cornucopia]

As stated earlier, all Mini-DV is 25 Mbs. DVC-Pro is 50 Mbs. Hardly able to tax any 1394 with 400 Mbs transfer rate.

Mini-DV, DV, DVC-Pro and DVCam are ALL 25Mbps.
DVC-Pro50 (which is 4:2:2, not 4:1:1) is 50Mbps, and probably doesn't use 1394 to transfer, but rather uses SDI (Serial Digital Interface?) protocol.
DVC-Pro100 is HiDef, 100Mbps, also using SDI.

Scott

[takeshi]

If I shot some video on a good 3-chip DV camcorder, perhaps a unit like
a Sony VX-2100, how could I export the video from the camera to capture
the completely uncompressed video you are referring to? The only other
option is the S-video connector.

You can't. It's written to tape in DV format which is compressed 5:1. I don't know if you can take uncompressed video through the svideo connector. It really depends on where the compression takes place along the path (probably well before video ever reached the svideo connector).

[edDV]

DV is also compressed, the ratio is 5:1

I've seen this 5 to 1 compression figure quoted before, interesting......

If I shot some video on a good 3-chip DV camcorder, perhaps a unit like
a Sony VX-2100, how could I export the video from the camera to capture
the completely uncompressed video you are referring to? The only other
option is the S-video connector.

Pro 3CCD cameras may provide full bandwidth RGB outputs. These are mainly used for advanced chroma key or color correction processes. Any output intended for human eyeballs will go through a 4:2:2 (pro Digital Betacam) or 4:1:1 (DV, DVCAM, DVCPro) YUV conversion.

S-Video is analog NTSC or PAL in Y/C form. The C contains U and V modulated around a color subcarrier. U and V are bandwidth limited to between 600Khz to 1MHz so are considerably more "compressed" than DV (1.7MHz) or Digital Betacam (3.7MHz).

Added Note: After detailed psychological testing, it has been concluded that the human eyeball can only resolve color at the equivalent of 500KHz to 1.2 MHz resolution depending on the color.

So most of us will be using a consumer version of the 25Mb/s DV format. For consumer and broadcast versions of DV, the 4:1:1 sampled camera output is further compressed about 5x by a mostly intraframe method so that quality frame editing will still be possible.

Adam Wilt's DV site goes into great detail on this
http://www.adamwilt.com/DV-FAQ-tech.html#DVformats

Here is a quick quote
"The sampled video is compressed using a Discrete Cosine Transform (DCT), the same sort of compression used in motion-JPEG. However, DV's DCT allows for more local optimization (of quantizing tables) within the frame than do JPEG compressors, allowing for higher quality at the nominal 5:1 compression factor than a JPEG frame would show."

There is also a "bandwidth distribution" feature in DV so that some frames can get more bandwidth than others due to a motion detection scheme.

Bottom line, DV is an editable, very high quality, lightly compressed professional quality format.

Does this mean that the analog S-video connector has a higher data
band-width than the 1394a output of a DV camcorder, with regard to
video previously recorded to tape? Or.... is the video recorded to tape
at the 5:1 compression ratio. It would seem silly to have an
uncompressed video stream coming from the CCD chips without any
method of exporting it before it is compressed.

It is possible to sample the S-Video output at very high data rates, but that doesn't mean you are getting higher video quality. Just the opposite because DV is a digital YUV component source that has not been encoded to NTSC/PAL. You will get lower quality Y as well as UV after decoding analog NTSC/PAL due to the Y-C crosstalk inherent in the NTSC/PAL encoding process. Even if Y is kept "pure" from UV contamination , you will still get losses after going through multiple 8 bit A/D, D/A conversions.