Recording in a less compressed/uncompressed format.
Posted 22 September 2008 - 04:09 PM
I've been pretty keen on the idea of recording material uncompressed or onto higher bandwidth tapes, but how big an advantage to this is there?
How much more flexibility in grading will I get? Will I see any difference before grading?
Possibly the most important aspect to me is latitude, will there be any real advantages when adjusting highlights/shadows with raw footage?
I haven't got any examples nor the computer to run the examples unfortunatelly, but if anyones got input on this I'd like to hear it.
Posted 22 September 2008 - 05:42 PM
However, in comparison with practical compressed formats you're actually likely to encounter in the wild, such as HDCAM and DVCPRO-HD, the differences are rather clear, and you'd generally only have to crank up the brightness of a monitor to see mosquito noise in the already noisy shadows.
It helps latitude not so much by giving you more latitude per se; the limit on video camera latitude is actually more noise in the blacks than it is highlight range, being as highlight range is determined only by where you choose to shoot mid-grey. It helps latitude because you can then use very aggressive gamma ramps - depending on the camera - which allow you to expose for highlights a lot more. You can do that on a compressed format, but a lot of your highlight range will be in such a small brightness range and end up so degraded by the compression that by the time you drag it all back down to a sane grade, it'll look like junk.
Posted 23 September 2008 - 05:28 AM
when it comes to bluescreen work do you think I'm better off shooting 1080i or 720p, in terms of keying? down rezzing to standard def after.
Edited by Daniel Ashley-Smith, 23 September 2008 - 05:29 AM.
Posted 23 September 2008 - 08:39 AM
Posted 23 September 2008 - 09:51 AM
Latitude is probably affected more by the camera than by the recording format generally. Most cameras are designed to output to a format that makes pretty good use of what they're getting off of the sensor. For instance, you can plug an SR deck (10bit) into an F900(HDCam, 8bit), but you're not actually capturing a greater bit depth; you're just mapping 8bit into a 10bit color space as far as I know. Compression is generally spatial; it looks to not record pixel data based on the surrounding pixels, but it's not going to go around changing brightness values.
What camera(s) are you thinking about using? A friend of mine recently shot a short with a Varicam and recorded it with a disc array- not totally uncompressed but I think ProRes, which is still a lot better than DVCProHD. He had a pretty good experience with it from what I heard.
Posted 23 September 2008 - 05:19 PM
This is more a computer question than anything, but as for building a server that can process hd-sdi, I've worked out the data rate to be about 1.054 gbits per second including 20% room. What's really confusing me is western digital hard drives, it says on their web site that even their 7,200rpm hard drives have a transfer rate of 3gbits per second.
But in every server I've seen built to take high quality video there has been a raid 0 array, but these hard drives appear to have a transfer rate which can handle hd-sdi.
Either I'm looking at the wrong thing here or new sata II hard drives can handle hd-sdi viewing in realtime.
what am I missing here?
Posted 23 September 2008 - 06:35 PM
Edited by Scott Fritzshall, 23 September 2008 - 06:36 PM.
Posted 24 September 2008 - 08:52 AM
Does anyone know of any performance data giving actual read/write speeds of hard drives? I've had a search but nothings come up.
It would be nice to not use 6 hard drives and get some 10,000 rpm drives instead but as they give no clue of the speed I don't know how many would be fast enough.
Posted 24 September 2008 - 12:04 PM
RAID-0 does tend to increase speed linearly, that is, two disks are twice as fast as one, but other RAID arrangements can have wildly varying speed between controllers.
Posted 24 September 2008 - 03:34 PM
I regularly get 70MB/sec out of decent modern SATA drives
is this from a 7200?
Posted 24 September 2008 - 05:17 PM
What makes the biggest difference in my experience is perpendicular recording, which is designed to increase density but as a side effect increases speed simply by causing the same speed of rotation to move more data beneath the head per unit time.
Posted 24 September 2008 - 05:36 PM
I'm looking forward to those solid state drives coming down in price, writing at 85meg per second and reading at about 130, SATA II with RAID support, four of them should go in a fairly cheap raid 5 motherboard and cover hd-sdi.
But really I'm only looking into being able to process hd-sdi, I'm not splashing out on a blackmagic card when I know it's just not worth it at the moment.
I just wish my college would realise that they're only getting about 10% of the three HDX900's potential by recording onto tape right now.
Edited by Daniel Ashley-Smith, 24 September 2008 - 05:41 PM.
Posted 24 September 2008 - 05:44 PM
writing at 85meg per second and reading at about 130
- not to mention the stupidly quick seek times, less than 0.35ms.