Is 35Mbs the Long GOP limit?
 

Does anyone know why Sony settled for 35Mbs as the data rate and whether if we buy into the EX series whether we could expect increased data rates (and therefore quality) in the future (eg by dialling it in)?

And why did they choose 4:2:0 - to protect more costly models? But I think the Panasonic HVX200 has 4:2:2 and its a budget HD model?

Is this why Scarlet will be revolutionary because it breaks the way Sony differentiates between quality and cost?

I just find all this quite baffling. Thanks

First let me say I am no expert here, but I think you are really missing a lot of the point of the camera.

No, 35Mb is not the limit for long GOP. But it is "good enough" for what this camera is supposed to do. In the same vein as saying that 120 mph is not the upper limit of speed for an SUV, but for it's intended purpose, that's more than enough.

The HVX200 does offer 4:2:2 color sampling, but it's doing that sampling on a much smaller picture. It does not read 1920x1080 like the EX1. It is reading 960x540. In terms of why 4:2:0, that's what the Mpeg2 profile the camera records in, dictates. In order to be compatible, they had to work inside the standard.

Scarlet will be revolutionary for a number of reasons. It will overscan the 1080 image we are used to. It will record with more color space. It will do a lot. And it will do it at an amazing price point. What Scarlet will not have is a native recording scheme that is compatible with what we all shoot now. It's like us all having CD players, and a new unit comes along that has DVDs. We can all make the jump, but it's not compatible with what we're doing now. Honestly, I think that's ok, but it's going to be a big change for some folks. Very few people will be able to edit 3k video on their current DV/HDV editing computers.

But you do realize that the EX1 has SDI output, right? Something very few other cameras in our price range can claim. This bypasses the 35Mbps 4:2:0 long GOP sampling and offers 1.5Gbps 4:2:2 "uncompressed" sampling just like the $150k cameras. Yes, the lens is nowhere near as good, and there are other differences as well, but the EX1 is fully capable of offering video quality other cameras in this price range couldn't dream of.

I think (although I don't know for sure) that 35Mb was chosen initially because it was a data rate that could easily be written to the discs used in the F350/F355 camera line.

I suspect it is 4:2:0 as that's how MPEG2 is normally encoded. While 4:2:2 MPEG2 is now possible it is not "normal".

Sure the HVX200 is 4:2:2 but the whole image is sub-sampled first. The numbers do not tell the full story. Perhaps it is 4:2:0 to protect high end products, but then HDCAM is 4:1:1 which has no more colour information than 4:2:0. In progressive 4:2:0 tends to look better than 4:1:1.

While Reds products are capable of producing stunning pictures and may well be cheaper per pixel than mainstream manufacturers there is more to it than that. For example where do you go to get a Red One repaired if it breaks and your not in the US? I have always found Sony's products to be well made, even at the cheaper end of their ranges.

The best bit is that we now have so much choice.

My guess regarding 35Mbps would be that it allows essentially same compression ratio as the xdcam HD 50Mbps spec, only with half as many chroma samples. Then again I think the 35Mbps XDCAM codec came along first, so im probably wrong. Not sure how exact those numbers are, and they are VBR from what i understand, so we are only talking about average compression ratios. As for whether they will allow increased data rates through firmware updates or new models... hard to really say. its not impossible. at least they give you the option of recording over HD-SDI however you want if you dont like the XDCAM EX compression scheme.

35Mbps certainly isnt any kind of limit on long GOP in general, if thats what you were asking. Look at convergent's XDR, they are encoding 100Mbps long GOP 4:2:2 video using sony's codec.

it is likely that 4:2:0 processing/encoding both protects the higher end product market and costs less for them to include in the camera. as for the HVX, all i can say is that color resolution when described in the color sampling notation (4:2:2) only means anything relative to luma resolution. I could take a video with my phone and scale it down and encode it as 4:4:4, doesnt mean it will look better, have better color, less artifacting, and pull keys better than something encoded as 4:2:0. in the case of the hvx perhaps it would be a better comparison if i said i could take a video with my phone, scale it UP, and encode it as 4:2:2, doesnt mean it will pull a key better than some video encoded as 4:2:0...

Scarlet is more revolutionary because it gives us RAW video workflow, 3k (probably ~2k practically), and 2/3" HD, none of which are really yet available otherwise under $10k with a lens. and $3k is well under $10k.

wow two people responded while i was writing my response, sorry if my post was redundant at all.

Perrone, appreciate response. I did say I was baffled. :-) So, the fact that you can do DVCPRO at 100Mbs on the HVX200 really isnt something i can compare the 35Mbs on the EX1 - they are just separate measurements with no relationship?

I dont understand the "good enough" - after all, they would simply have an even more incredible camera if the data rate was 70Mbs (and associated increase in pic quality) wouldnt they? I understand Alistairs point on the limitation of SxS cards - that implies that unless you get faster cards you cant increase the data rate I think.


If we ignore for a moment camera handling, support, familarity, accessories and whatever else people use to make decisions to buy a camera and focus on just 1 thing - picture quality - if I want to output to (a) DVD (b) Blue-ray outputs - why on earth would one purchase a HVX200 or 201? Are there situations where the 4:2:2 colr space gives me some sort of advantage, eg, an indie movie as opposed to ENG?

Got it. They are re-writing the rules. I assume we will be able to use scarlet though at 1920x1080 with Red compression? I dont need 3K, just "as near to" uncompressed HD and 4:2:2 (I think)

Sorry, didnt know that. But why the massive jump to producing massive uncompressed data files? Why cant we dial-in the compression we want coming out of the EX? It doesnt sound like my current quad-core would cope with 1.5gbps either?

sxs cards can certainly handle more than 35Mbps. Slow motion footage is written to the card at quite a bit more than 35Mbps. 35Mbps sounds like it might be a limitation of the original optical media used for XDCAM. that number is pretty close to the higher end of the specs for blu-ray delivery in mpeg2 i believe, so that might be an indication that the discs or encoding/decoding equipment may have been limited to about 35Mbps at the time... just a guess

Let's take these one at a time...

DVCProHD is 1280x1080. Not 1920x1080 like on the EX1, and not 1440x1080 on HDV. THat is how they fit it inside the 100Mbps. If they were doing 1920 instead of 1280, they'd need 160mbps. But remember, the HVX can't see 1280 either. So they use their technology to make the pixel sensors put together a 1920x1080 signal, then scale that down to fit inside a 100mbps stream of DVCProHD.

Reference here: http://www.mediacollege.com/video/fo.../dvcprohd.html


The SxS is certainly fast enough to record 100mbps or even 160mbps. That is not a limitation. If the EX1 could record at 70mbps, you'd have your choice of a 8GB card for $899 that could record 12 minutes of video, or a 16GB card for $1599 that could record 24 minutes. In the EX1 price range, it's pretty hard to sell a camera that took $3200 worth of memory and still couldn't record an hour of video. At the levels where people are paying $100k for a camera, this might be more feasible. Ever take a look at the recording times for the HVX on P2 with DVCProHD? Sixteen minutes on a 16GB card. Unless you're shooting scenes for films, or on a broadcast budget where you can afford $10k in cards, that's pretty limiting.


Because when the HVX was released, there was NOTHING even close on the market within $20k of it. It was revolutionary. Especially with the ability to under and overcrank at 720p. The nearest cameras that could do that were the Varicams at about $80k.


Yes, you can use Scarlet at 1920. In fact, I'd be that you won't get much more resolution than that period. Maybe 2048x1024. If you want uncompressed 1080 with 4:2:2, you've got it with the EX1. It's built in.


The "massive jump" is an industry standard. Sony essentially produced a camera that offers two standards. One that can be used to record excellent quality video images at HDV or slightly better than HDV standards. The other that gives performance on par with their $100k cameras. And they give you both in a sub $10k camera. In terms if "dialing in" compression, I am not aware of any video camera (or film camera), at any price that allows you to do that. You can change the frame rates, you can change the gamma. But changing the compression ratios on the fly... never seen it.

HD-SDI video is no joke to fool with in post. That's for sure. But neither is RED's 4k. There are ways around this. Like working with proxy files. When films are cut on computer, generally they are edited with proxy files that are much smaller. Cutting on 720p proxies is MUCH easier. So you do that, then apply all changes to the original media, and let it render. That's actually how I've been dealing with 1080p files on my older workstation. At least until I started using Cineform.

If you are willing to go with an outboard recorder, the Convergent Design's new products will allow you to record 4:2:2 Mpeg at 50 Mb/sec, 100 Mb/sec and 160 Mb/sec (this one is all I frames, the others are long GOP) from the EX1 (or other cameras) HD-SDI out.

http://www.dvinfo.net/conf/forumdisplay.php?f=166

The devices use the same codec chips as in the Sony cameras, only pushing the chips to their full potential, and give a glimpse into the possible recording option of future Sony cameras in the Prosumer line... but allowing you to access that potential today.

Regards,

Jim Arthurs

I think Sony did this EXACTLY right.

Give you HDV off the Firewire port, give you XDCam to onboard recording, and give you HD-SDI out for high end off-board recording. Something for every market. Very flexible. If Sony had gone to the 100mbps or 160mpbs for their onboard codec, the recording times would have been horrifically short and VERY expensive. Like the original 2GB P2 cards, or the original Compact Flash cards in the RED. Very few people are going to be happy spending $800 to get 4 minutes!

Just a note that the second paragraph in my quote in the above reply are your thoughts, not mine. No problem, I think you just didn't seperate my statements into two parts when you quoted me...

Regards,

Jim Arthurs

Sorry Jim, I missed it.

I know you know this, Alister, but I wanted to make sure folks were clear. HDCAM is like 3:1:1 sampling ratio.

-gb-