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HD Downconversion
Thanks in part to Blackmagic, with whose hardware we produced our last few years’ work, we just got our first 35mm commercial.
It is to be broadcast in SD and so we are planning on the following moves:
Investing in a Dual 2.7 G5 with all the trimmings.
Investing in a Decklink HD card.This will slide in nicely to the space our older Dual G4 sat, just next to the Apple RAID.
A question about workflow:
I’m planning on shooting at 25fps (we’re in PAL land) either open gate and wastefully cropping to 16/9 or 3 perf and slightly less wastefully cropping to 16/9 then asking for a telecine to digital HD media.
So the first question is:
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4 Replies
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I don’t know why but that post got titled strangely when I submitted it.
The original title was ’35mm And HD Workflows’ which sounds much more exciting.
And .. we can’t edit our posts?
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Hi,
There are about 1000 things to wach out for….
1. To wich format to telecine, If you need full raster HD or some hevy dudy color grading then HDCAM SR and some disk recorder are the only way to go – here is why:
HDCAM SR is full raster meaning 1920×1080 and has color depth of 10bit (HDCAM is 1440×1080 and 8 bit)
HDCAM SR has much better compression (even 4:4:4 RGB option and 4:2:2) HDCAM has only 3:1:1 and more artifacts on blacksThere are also some bad disk recorders that introduce some artifacts from internal compression – so make sure it DOES NOT compress picture, or test the compressed picture in some CC aplication and maks sure you have good information in the dark area of the picture and white clip shouldn’t be to sharp
NB there is no 1080 25p standard in HD there is only 50i (put this is not a problem becuse bot fields are from the same frame so you will end up with the full frame anyhow)
2. Codec – it depends how much space you have and how fast array you got – you said you will preform the final CC yourself so ONLY 10bit codecs (and up) will do
4:4:4 RGB codec is superior but it requires 1/3 more bandwith and you have to render evrything outside FCP because fcp can RENDER RGB only in 8 bit – if you choose 10bit uncompressed (be it apple or BMD) then you will not have the problem – but it is much harder to pull decent keys and CC is bit more triky as wellI think you should get the HW you plan and maybe get a demo from telecine house (just few minutes of any footage in the specs you plan to do the job) and TEST TEST TEST TEST TEST – don’t risk to look like a fool in front of your client
(I know I started the same road about a year ago and there are many caveats on road, so planning and testing – just planning is no good)-Kaspar
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Hi Nic,
That’s great news about your 35mm commercial – congratulations!
[Nic Alderton] “What’s my best choice of codec?”
In Final Cut Pro HD 5.0, we have adopted the Apple codecs for all 4:2:2 work in SD & HD. Apple have added HD color space to their 4:2:2 codec so there is no longer a need for the Blackmagic codecs in 4:2:2. We do however still include the Blackmagic 10-bit RGB codec for 4:4:4 work which you might need with a telecine or a Sony HDCAM SR deck. This is because Apple do not yet have their own RGB codec for HD.
So if you’re going to work in 4:2:2 SD or HD, then you can use the Apple uncompressed 4:2:2 codec. If you are going to work in 4:4:4 HD, then you can use the Blackmagic 10-bit RGB codec.
[Nic Alderton] “1080p25 would be my first choice”
Kaspar’s comments are well worth digesting. Please also review the technical note entitled
Does DeckLink HD support HDTV1080p/25 in Final Cut Pro?[Nic Alderton] “Wil the Decklink HD card will allow us to monitor in realtime on our SD studio monitor?”
Yes, all of the DeckLink HD series cards will enable you to work in either SD or HD. In addition, all of the DeckLink HD series cards have down conversion capabilities which are documented in the technical note
Software and hardware down conversion with DeckLink cards.
In fact even your existing DeckLink Pro has down conversion capabilities when playing back HD video on your dual G5/2.7 GHz.When you first install a DeckLink HD series card, the extended desktop will default to a HD mode which of course won’t display on your SD monitor. We’ve documented the steps for changing the extended desktop to standard definition (720 x 576, 25 Hz for PAL) in a technical note entitled Can a SD monitor be used with DeckLink HD and Mac OS X?.
If you are going to be capturing or playing back uncompressed HD material, then you are going to need a HD-capable disk array. A fully populated Apple Xserve RAID (14 disks and at least 512 MB of RAM on each RAID controller) will usually support HDTV Uncompressed 10-bit 4:2:2 but a faster disk system would be required for 4:4:4, eg eight U320 SCSI disks RAID’ed together.
If you are testing disk storage, fill it up to about 80% of capacity and then run your tests as this will slow down the performance significantly and should give you a real-world idea of whether the disk array is fast enough for your needs.
Kaspar’s comments about planning and testing are very good comments. If you find that you do not have enough disk capacity for capturing HD video, you could consider capturing to a Blackmagic HDTV 1080i/50 DVCPRO HD timeline. The compressed DVCPRO HD codec provides very impressive quality and DeckLink cards support down conversion from both 8 and 10 bit HD timelines as well as from DVCPRO HD 🙂
Regards,
Luke Maslen
Blackmagic Design -
Thanks Kaspar and Luke
Lots of good info and plenty to think about there.
We can actually play back 1080i50 footage on the humble dual 1.42 G4 with our current RAID, so with the faster machine we should be fine.
My first thought was to avoid having the telecine run to tape and instead ask for the footage to be saved directly to a portable hard drive, with a tape as a safety. We would have to confirm with the telecine house that they could provide the codecs we require.
We won’t be keying anything, so we could reasonably stick with 4:2:2 1080i50 which would finally be downconverted to an SD master. In the future, if we move up to 4:4:4 we’ll have to get the top of the range BM card and a new RAID anyway.
A couple of extra thoughts:
Our X-Raid will be fully populated and already has 2×512 caches, however it was striped under Disk Utility in 10.3. I seem to recall reading somewhere that stripes performed under 10.3 will perform 10% slower under 10.4 and that a restripe is in order. Any confirmation on this?
What is the current situation with Apple’s undocumented gamma corrections when coming to and from their uncompressed codecs?
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