Capturing uncompressed HD

[Trevor Allin]

Hi

I purchased the GY-HD101 a few weeks ago (love it!). I am mostly doing chroma-key work and would therefore appreciate the benefoits of working with an uncompressed signal. Can anyone recommend the least expensive way to capture uncompressed HD from the 101 either to my G5 Mac or 2.8ghz laptop?

Thanks.

Trevor

[Tim Dashwood]

I just successfully did it last week with a Decklink HD system on a Dual 2.5 G5 equipped with a Decklink Multibridge (for analog to SDI conversion)

It worked great, but you have to remember that you can only get true uncompressed when shooting "live," not playing back from tape (since the signal has already been through the MPEG2 encoder.)

The other thing is that when in 720P30 mode, the analog component outputs send out 720P60. This is great for shooting true HD slow-mo.
When the camera is in 720P24 mode, the output is 720P48. I captured this stream with the 720P60 decklink preset and it had a pulldown of 4:1.
I assume 720P25 can be captured in a 720P50 stream? I didn't test 25P.

[Trevor Allin]

Hi

Thanks for the reply. A couple of further questions then..

(1) What was involved in the deck link set up and any idea of rough kind of price?

(2) How are you capturing live onto your Mac? I can capture live on my windows laptop using Serious Magic's DV Tack. But I don't htink I have anything to capture live on my Mac. I use Final Cut Pro 5.

Thanks

Trevor

[Ken Hodson]

So it captures the 24p fine then? What about the SD modes? Can it capture 480p60?

[Tim Dashwood]

Originally Posted by Trevor Allin

(1) What was involved in the deck link set up and any idea of rough kind of price?

I was specifically using Decklink HD PRO 4:4:4 ($1495 U.S)
http://www.decklink.com/products/hd/

and the Multibridge HD ($1995 U.S.) to convert the HD anolog out to SDI.
http://www.decklink.com/products/multibridgeconverter/

digitizing to an Xserve RAID ($8000 U.S.)
http://www.apple.com/ca/xserve/raid/

Keep in mind this system is in a post-house, so not the kind of thing you would be able to cart out to location to record uncompressed HD. The only really useful application would be clean green-screen shooting in a studio.

Originally Posted by Trevor Allin

(2) How are you capturing live onto your Mac? I can capture live on my windows laptop using Serious Magic's DV Tack. But I don't htink I have anything to capture live on my Mac. I use Final Cut Pro 5.

I was also just using FCP 5. Just turn off deck control and then "capture now" using a Decklink 720P60 preset.
You could also capture live HDV in 720P30 mode with FCP5. I've done that before, but anything going down the firewire is in no way 'uncompressed.' Same goes for DV Rack. You can transcode into an uncompressed codec, but the image has already gone through one stage of MPEG2 4:2:0 compression.

[Ken Hodson]

Would you need the Decklink HD PRO 4:4:4 or would the less expensive Decklink HD PRO 4:2:2 be ideal? Is the analog component out of the cam 4:4:4 or is it 4:2:2?

[Tim Dashwood]

Originally Posted by Ken Hodson

Would you need the Decklink HD PRO 4:4:4 or would the less expensive Decklink HD PRO 4:2:2 be ideal? Is the analog component out of the cam 4:4:4 or is it 4:2:2?

Good question. Is the analog output of the HD100 created from a 4:2:2 or 4:4:4 source? I don't know for sure, but common sense says to me that it is actually only 4:2:0 - since the colour space is probably a property of the CCDs (at the time they are scanned) and image processor and not the MPEG2 encoder. Maybe someone "in the know" can confirm this for us.

Either way, the 4:4:4 is definitely overkill for most HD formats. Typically I am digitizing HDCAM originated material or 35mm to HDCAM film transfers, and standard HDCAM is only 3:1:1.
I've never actually used the 12-bit 4:4:4 because it requires dual-stream SDI, and I've never worked with any sort of deck in that format. Also, it eats up hard drive space like crazy. I suppose 4:4:4 12-bit would be used with something like a Thompson Viper.

So I guess the short answer is that 4:2:2 would be fine. Blackmagic makes three flavours of Decklink HD in 4:2:2 starting at $595.
You might even be able to find a much cheaper analog component to SDI converter.

[Trevor Allin]

Thanks Tim, thats really helpful.

Would does SDI mean? And I am doing green screen work with the HD101 so any idea whether it would be worth getting the 4:4:4 version of deck link or would it be overkill?

Trevor

[Marc Colemont]

SDI - Serial Digital Interface.
In a few words it is the digital version of the Composite signal (format is different YCrCb though) which can be transmitted on the same common Coax cables used for Video.
Since it is digital, you have no quality loss of the signal on long cables and 50/60 Hz video hum is gone between devices which are connected on different power sockets.
The video format is the SD signal 720x480 NTSC / 720x576 PAL 270Kbits/sec.
The HD signals are possible with the HD-SDI signals upto 1,48 Gbits per second.
Capture cards which have SDI/HD-SDI input don't use analog components to capture the video which gives better quality through less conversions to digitize the video signals.

The YPrPb signal coming out of the HD100 (sometimes wrongly refered as YUV) is the analog version of the YCrCb.
So if you have a capture card who has digital inputs (HD-SDI or SDI) you need concersion boxes. It's best to keep the analog signals as short as possible and do the conversion close to the camera and use the SDI/HD-SDI with longer cables to connect to your other equipment

[John Mitchell]

Originally Posted by Tim Dashwood

Blackmagic makes three flavours of Decklink HD in 4:2:2 starting at $595.
You might even be able to find a much cheaper analog component to SDI converter.

You could also try the Kona card - they make a version which includes analogue inputs - a Mac guy could tell you if these things are any good but they would do away with the need for an HD-SDI converter:

http://www.aja.com/products_kona.html#lh

and because it includes DVCProHD hardware support it would require much less processing power, and disk space.

They also make a mini SDI converter if you want to go with the Decklink card:

http://www.aja.com/hd10a.htm

and finally they make a Windows version that at this stage only supports uncompressed codecs:

http://www.aja.com/products_xena.html

The other place to look is Miranda but I have always found them to be more expensive.

[Trevor Allin]

Thank you gentlemen, vey helpful.

Trevor

[Serge Victorovich]

Originally Posted by John Mitchell

and finally they make a Windows version that at this stage only supports uncompressed codecs:

http://www.aja.com/products_xena.html

The other place to look is Miranda but I have always found them to be more expensive.

With XenaHD you can capture also to CFHD.
http://www.cineform.com/products/ProspectHD.htm

[Alex Bowles]

So let me get this straight - the signal coming out of the component jacks is uncompressed 8-bit NTSC (or PAL, of you've got the 101) with 4:2:0 color sampling, right?

More importantly, has anyone tried Tim's hypothetical green-screen studio setup? I'm wondering if the 4:2:0 (specifically, the '0') would cause grief when attempting to pull the keys shot on said stage.

I'm hearing that post houses are doing fine chroma key work with properly lit greenscreens shot at 4:2:2 (e.g. 4:4:4 may only be necessary for the most demanding situations) but I'm wondering if the otherwise immaculate signal provided by Tim's workflow (only one A/D conversion) would be fatally undermined by too little chroma sampling at the outset.

[Stephen L. Noe]

Originally Posted by Alex Bowles

So let me get this straight - the signal coming out of the component jacks is uncompressed 8-bit NTSC (or PAL, of you've got the 101) with 4:2:0 color sampling, right?.

No, that is not straight (the 420). That is a theory and not confirmed. I have chromakeyed with HD-100 content using Primatte, Boris and Liquid YUV (uncompressed) with very nice results. Do you have some camera footage to try chromakey? What keying software do you use?

[David Newman]

No, the component signal is a full 1280x720 4:2:2 sampled at 10-bit, plenty of chroma resolution to pull a great key. See indiefilmlive.blogspot.com for discussion regarding an effect heavy feature that is using the HD100.

Note: 100 and 101 have both 50 and 60p modes, there is no PAL or NTSC here.