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AVCHD Format Discussion
Inexpensive High Definition H.264 encoding to DVD, Hard Disc or SD Card.


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Old January 3rd, 2007, 10:52 PM   #1
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Bypass AVCHD with HDMI

BlackmagicDesign has a PCI card (intensity) that has an input HDMI port, and a output HDMI port. If I am understanding their info correctly, you are able to import lossless HD into your computer via the HDMI out port on your HD cam, for example I have the HDR-SR1 with a HDMI port. BlackmagicDesign claims there is no compression due to the fact that the HDMI signal is before the compression chip in the HD cam. From what I have read, AVCHD is a highly compressed file, therefore it is very CPU intensive to decompress as compared the the HDMI signal which is not compressed and requires very little of the CPU.

I realize that downloading in this manner (1:1) is like going backwards but at least it is not compressed, and we can begin working with our HD video now instead of waiting for AVCHD support in software. I could be totally wrong in my understanding on this, so please dont hesitat to correct anything I have stated above.

Does this appear to be a good card to buy? I would love to here everyones view on this.

Below is a link to the blackmagicDesign site.

http://www.blackmagic-design.com/products/intensity/
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Old January 4th, 2007, 04:24 AM   #2
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The only downside is you'll have to lug a PC (or mac) if you plan to do field work.
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Old January 4th, 2007, 06:24 AM   #3
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If you shoot video to the camcorder's hard drive, the video is in highly compressed AVCHD format. You can then play that back over HDMI and capture it with that Black Magic card, but its quality is only as good as the original compression and decompression chips/firmware in the camcorder. Sure, it gets you around having to decompress the video using the computer but it also substantially increases the storage space required for the video. Now, I suppose you can just capture from the HDMI port without recording to the camcorder's hard drive (or simultaneously while recording), but, as Jack points out, now you have to lug a computer around to capture the video.
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Old January 4th, 2007, 08:51 AM   #4
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There have been topics about this for awhile now. What I dont understand, is how come companies like Firestore arent making portable devices like this. I mean a portable disk connected to the HDMI port that allows the capture of Uncompressed HD??!? Yea, Id buy that.

-burk
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Old January 4th, 2007, 10:05 AM   #5
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For the simple reason that it is physically impossible. On the one hand since it would require a sustained write speed of about 200 MB/s, which can only be achieved with a large raid array, on the other because the HDMI output is only the compressed MPEG2 4:2:0 signal @ 25 Mbps, as confirmed by Sony.

HDMI is just a transport mechanism, like fire wire. It allows for digital transfer of data from a source to a destination, nothing more.

The fact that HDMI allows faster data transfer rates does not mean they have been implemented in the camera. Fire wire connections allow either 400 or 800 MBps transfer rates, but fire wire disks do not allow that data rate, due to physical limitations. Same applies to the HDMI implementation of Sony.
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Old January 4th, 2007, 11:02 AM   #6
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So its not impossible, it's impratical at the moment right. If what you say is true, that means that if somebody were to design a fast enough raid array that were small enough to fit in a case that was the size of a Tablet PC, then you could cover the size issue. I mean, I could find a way to mount something like that to a tripod or something. With the advances these storage companies have made, I find it hard to believe that this is impossible. It might be expensive, but not impossible.

As far as the HDMI output only being compressed MPEG2 4:2:0 signal @ 25 Mbps, how are other people able to pull uncompressed HD with intensity and other cards?
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Old January 4th, 2007, 12:16 PM   #7
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Quote:
Originally Posted by Jason Burkhimer
As far as the HDMI output only being compressed MPEG2 4:2:0 signal @ 25 Mbps, how are other people able to pull uncompressed HD with intensity and other cards?
Using HD-SDI.
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Old January 4th, 2007, 12:50 PM   #8
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I gotcha. I thought that thru HDMI to HD-SDI converters, people were capturing uncompressed HD footage from the HDMI port. Thats what i gathered from Dave Nelson's comments in this thread anyway:

http://www.dvinfo.net/conf/showthrea...i+uncompressed


Hopefully some kind of setup like I was mentioning isnt too far in the future though!

-burk
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Old January 10th, 2007, 09:39 AM   #9
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Quote:
Originally Posted by Harm Millaard
For the simple reason that it is physically impossible. On the one hand since it would require a sustained write speed of about 200 MB/s, which can only be achieved with a large raid array, on the other because the HDMI output is only the compressed MPEG2 4:2:0 signal @ 25 Mbps, as confirmed by Sony.

HDMI is just a transport mechanism, like fire wire. It allows for digital transfer of data from a source to a destination, nothing more.

The fact that HDMI allows faster data transfer rates does not mean they have been implemented in the camera. Fire wire connections allow either 400 or 800 MBps transfer rates, but fire wire disks do not allow that data rate, due to physical limitations. Same applies to the HDMI implementation of Sony.
I'd like someone other than me to chime in here. Chris, Spot...

HDMI is not a just a computer data transport. It is an a protocol for an uncompressed digital video signal. I have no idea what Sony does in this class of camera (and would like to find out). However in the V1/FX7, HDMI bypasses HDV compression. It uprezes a 1440x1080 4:2:2 signal to 1920x1080 and sends it out uncompressed.

To capture it on a Firestore type device would require either incredible bandwidth (currently requiring an array), or a very powerful processor to compress it in another format. I believe the BlackMagic Intensity card has software to do that. Again...input is needed from someone more knowledgeable than me.

David

Update:

From BlackMagic-Design:

Quote:
Online JPEG for Adobe Premiere Pro™

On Windows, Blackmagic's full resolution (1920x1080) professional quality compressed HD codec can capture JPEG AVI files in real time using Premiere Pro. Unlike HDV and DVCPRO HD which uses reduced resolution 1440x1080 video, Blackmagic's Online JPEG maintains the full resolution 1920x1080 resolution of HD video without the huge file size of uncompressed HD video. Blackmagic's Online JPEG is so efficient that full motion 1080i HD video can be recorded at only 12 MB per second vs. a massive 119 MB per second for uncompressed HD video.

Blackmagic's compressed files are so compact, that 1080 HD video can be captured to a single internal hard disk or easily transported on a portable Firewire drive! Online JPEG is compatible with Adobe Premiere Pro and After Effects and can even be used by editors without Blackmagic capture cards making it one of the most versatile compressed codecs available.
Update 2:

Apparently you can get HDMI cables in really long lengths. Hundreds of feet. However, the appear to have amplifiers or repeaters and are several hundred dollars. That would allow you to walk around a house or office a record to a PC in a single location. To use a laptop, you would need a docking station that including a PCI slot r or a PCI extender chassis for a laptop, which is can be expensive.

Last edited by David Ziegelheim; January 10th, 2007 at 10:19 AM.
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Old January 18th, 2007, 09:45 PM   #10
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Harm Millaard, where is this information - I'd like to be able to read more about this - Sony's implementation.

Quote:
Originally Posted by Harm Millaard
...on the other because the HDMI output is only the compressed MPEG2 4:2:0 signal @ 25 Mbps, as confirmed by Sony.
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Old January 21st, 2007, 11:09 AM   #11
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HDMI is about 100MB/s at 8bit 1920*1080, and less at 1440. At 2:1 lossless it is half, at 4:1 (very few codecs) lossless half again. With cineform they achieve something like 6:1 to ten to one visually lossless (serious money). Very fast hard drives can do 50Mbytes/s for the last few years, so might be faster now. Last I checked I think their were laptop drives that would do 25 or 36Mb/s, but that would have been a year ago.

So, it is possible, but some compression would be advised, even 4:1 to 6:1 lossy. Uncompressed however is an bigger problem.
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