Sony X70 4K - Lowest bit rate in the industry!

[Cliff Totten]

So really, all of the 1080 features work as normal with the firmware and paid 4K upgrade.

Sony disabled some features to open up CPU headroom room for 4K tasks. I'm perfectly fine with this! If Sony gives the X70 at 4K, 100Mbp/s in the future, I'd GLADLY disable "Face Tracking", IP streaming, WiFi, Android control and a few other features I wont use. If I need that stuff, I'd drop back down to 1080.

Oh,..the 4k to 1080 live down convert on the SDI...if it will save CPU for 100Mbp/s?...disable the SDI completely and I'll be fine. It's only 3 gig anyway and cant do 4K.

What I really care about is having "good" 4k. as both, an AX100 and X70 ownner. There is a HUGE difference between 60Mbp/s and 100Mbp/s when color grading both bit rates.

The PXW-X70 needs 100Mbp/s badly. Sony can leave all the other fun fluffware features untouched in 1080 mode.

Buy the way, the AX100 today will not let you record internally at 4k and HDMI at the same time either. (you get one or the other, not both)

[Paul Hardy]

Ok guys - I'm trying to get a handle on genuinely how bad 60mbps actually is from those far more in the know than I.......

Am I correct in assuming that 4K 25p will in theory be a slightly higher bitrate per pixel than the AVCHD 1080/50p at 28mbps (28mbps divide by 2 to account for fps times by 4 = 56mbps)??

[Ricky Sharp]

Originally Posted by Paul Hardy

Ok guys - I'm trying to get a handle on genuinely how bad 60mbps actually is from those far more in the know than I.......

Am I correct in assuming that 4K 25p will in theory be a slightly higher bitrate per pixel than the AVCHD 1080/50p at 28mbps (28mbps divide by 2 to account for fps times by 4 = 56mbps)??

Kind of. The frames per second doesn't change the bit-rate though. But it will change the compression ratio. i.e. at 28 Mbps, 25p footage would be half as compressed as 50p footage.

Edit: Hmm.. I think I see where you were going with your calculation though. Assuming the 28 Mbps 50p footage looks decent, then 60 Mbps 4K 25p footage should not contain any more compression artifacts.

Rough calculations taking into account that both sets of footage would be 8-bit 4:2:0

Your AVCHD 1080/50p @ 28 Mbps would have a compression ratio of 42:1
The UHD/25p @ 60 Mbps should have a compression ratio of 39:1

For the compression ratio, I took the number of bits required to store one second worth of the footage in 8-bit 4:2:0. Then divided by the recording bit rate.

Is the AVCHD footage at 50p really just using 28 Mbps though? I had thought it would be more like 35.


For comparrison sake, 10-bit 4:2:2 XAVC footage seems to have these compression ratios (assuming my math is correct):

25p: 20:1
30p: 24:1
60p: 47:1

[Cliff Totten]

As an extremely rough "rule of thumb" with h.264:

If you have 1080 at 30p encoded at 24Mbps "AVCHD", you get a certain quality. If you multiply that times "4" for UHD resolution, you get "roughly" the same quality equivalent in UHD. (Yes, I know with Long GOP and block size, this is a bit debatable)

So....

100Mbp/s UHD is similar to 25Mbp/s in 1080p

60Mbp/s UHD is similar to 15Mbp/s in 1080p

"Similar to..." simply means the codec's ability to deal with motion and sharpness per pixel blocks. I'm fairly certain the block size and math stays the same with H.264 no mater it's resolution. In other words, h.264 doesn't really get significantly more "efficient" as the frame size gets larger or smaller, (1080 to UHD using the same baseline,Main or high profiles with CABAC enabled )

This is not just "math"...it's also very visually evident when you compare with your eyes...especially on zoom/crops. Color grading the two bit rates is also VERY different as well.

So yeah, UHD at 60Mbp/s is really only 15Mbp/s per 1080 quadrent...very low indeed and this is why No Panasonic, Canon, JVC or any other Sony camera uses 60Mbp/s today!!!! (and with very good reason)

At 60Mbp/s, the PXW-X70 is really sitting all by itself at the BOTTOM of the industry UHD bitrate list. It is using a bitrate that even the cheapest consumer camcorders stay far away from.

[Paul Anderegg]

Where can I buy this 4K upgrade? I clicked the Sony link in the firmware 2.0 download section and it took me to Service Plus homepage, can't find where to purchase the damn thing.

I am arranging a demo HM200 with JVC, so would like to put the 2 cameras up against each other possibly.

Paul

[David Dixon]

Paul, it's not released yet. This week's free firmware 2.0 will be required for the 4K update which is rumored for June 15. Undocumented fixes in 2.0 include that XAVC-L is finally natively compatible with FCPX, and it offers a fix for a rare problem of the camera locking up when shooting with 2 cards simultaneously.

[Paul Anderegg]

Oh, OK, my demo would be for June 30, so let's see how that works out.

Paul

[Zenes Petrusin]

Hello,

has some technical answers, i own service manuals of CX900, AX100 and X70. All this camcorders is basicaly indentical inside, but has some little difference. Main difference is CPU, CX900 and AX100 use same cpu called IC6000 MSZ4G4G02C , this is CPU, CAMERA DSP, AV SIGNAL PROCESS, LENS CONTROL, MODE CONTROL, HDMI PROCESS. X70 has this CPU called IC6000 MHZ4G8G11A, internal specification say of this cpu more performance, more features as in CX900, AX100. Sony says about bitrate "We are looking to support a higher bit-rate recording mode than 60 Mbps for 3840x2160 XAVC-L in the future."

I think all is marketing and want sell more ax100, then add more bitrate.

And this is more specification about cmos chip in CX900 AX100 X70, btw. this chip can do 4K video mode (4096H × 2160V, 60 frame/s)

http://www.sony.net/Products/SC-HP/n.../imx183_e.html

[Dave Blackhurst]

Since 100Mb/s is already "in" the AX100 (and looks excellent), as well as the "consumer" AX33 and X1000 Actioncam (looks OK, but limited by the tiny sensor, IMO), there really shouldn't be any reason the X70 doesn't get that rate when 4K is added, IMO.

Interesting speculation that Sony "could" squeeze even a bit more out of the processor/sensor combo... UHD, 60P at higher bitrates... hmmmm. Oh to have a "fly on the wall" at the Sony "mad scientist laboratory"!

[Cliff Totten]

Dave, +1

I might buy into the fact that the X70 needs a higher CPU than the AX100.

4K Codec aside, it's possible that the X70 truly IS doing more calculations per second than the AX100. I'm sure picture profiles, dual card writing with proxy, WiFi control with streaming encoding all eat more CPU cycles.

In fact, I have both models right here next to me and I have been doing back and forth testing this weekend. The X70 certainly eats Sony VF100 batteries SIGNIFICANTLY faster than the AX100. I have noticed this with three different Sony batteries. I'd guess that the X70 drains batteries 35% (or more) faster when shooting 1080 than the AX100 does in 4K. I was quite surprised by this.

Could this X70's higher processor have more cores or run at higher clock speeds?

I have said this before, if the X70 needs WiFi control, face tracking, proxy and dual card recording and IP streaming shut off to achieve reliable 100Mbp/s 4K?...I think it's absolutely worth it. How often does anybody control their X70 with the mobile app? How many people do IP streaming? How often do you use the cameras codec?...every day you shoot, right?

Without a solid recording codec, you have nothing in any camera.

[Paul Hardy]

So Sony have just released the RX10 mk2 & the RX100 mk4 Pocket camera - both with 100mbps 4k recording & we have to pay £499 for ****ing 60mbps. Seriously now considering selling my X70's & buying some JVC's

[Ron Evans]

The new NX100 uses the older NP760 batteries which are much larger and maybe is a better form factor for the X70. Again not sure the logic of Sony product management/marketing is at the moment. Seems to me a more feature rich version of the NX100 would be a better model than the X70 and therefore not need the X70 in the lineup at all.

Ron Evans

[Jody Eldred]

Originally Posted by Paul Hardy

Don't forget that although 60mbps is low - it doesn't quite equate to 15mbps at Full HD due to the compression algorithms (IIRC the maths from a sony seminar when HD first came out - it would actually be a little higher than 15mbps as an equivalent!)

Actually - No, who am I trying to kid??, it's uselessly low & It should be a minimum of 100mbps.

Grab the torches & pitchforks and we'll all meet up outside the Sony HQ!!

I know the math, but, respectfully, do you know the images? I am shooting 60 Mbps 4K with the X70 and it looks OUTSTANDING. I viewed a lot of my footage on a 4K monitor with a respected colleague and we did not observe said compression artifacting. (I own an F55 and have shot many 4K Raw and S-Log projects, so I have a very good basis for comparison.) The bottom line is not algorithms and equations, but how the images actually LOOK, and is your client and audience happy with them. All else is purely academic.

Here is some of that 4K footage (obviously compressed for YouTube):

Sony PXW-X70 4K field test: Jody Eldred DP/Editor - YouTube

https://www.youtube.com/watch?v=vx3t...ature=youtu.be

Meanwhile back at the ranch... the Sony X70 shoots 'em up in 4K - YouTube

[Jody Eldred]

Originally Posted by Cliff Totten

As an extremely rough "rule of thumb" with h.264:

If you have 1080 at 30p encoded at 24Mbps "AVCHD", you get a certain quality. If you multiply that times "4" for UHD resolution, you get "roughly" the same quality equivalent in UHD. (Yes, I know with Long GOP and block size, this is a bit debatable)

So....

100Mbp/s UHD is similar to 25Mbp/s in 1080p

60Mbp/s UHD is similar to 15Mbp/s in 1080p

"Similar to..." simply means the codec's ability to deal with motion and sharpness per pixel blocks. I'm fairly certain the block size and math stays the same with H.264 no mater it's resolution. In other words, h.264 doesn't really get significantly more "efficient" as the frame size gets larger or smaller, (1080 to UHD using the same baseline,Main or high profiles with CABAC enabled )

This is not just "math"...it's also very visually evident when you compare with your eyes...especially on zoom/crops. Color grading the two bit rates is also VERY different as well.

So yeah, UHD at 60Mbp/s is really only 15Mbp/s per 1080 quadrent...very low indeed and this is why No Panasonic, Canon, JVC or any other Sony camera uses 60Mbp/s today!!!! (and with very good reason)

At 60Mbp/s, the PXW-X70 is really sitting all by itself at the BOTTOM of the industry UHD bitrate list. It is using a bitrate that even the cheapest consumer camcorders stay far away from.

Math is one thing, but have you SEEN the 4K images? Don't you think that calling out Sony as having a worthless codec and a poor quality camera simply on calculations and not actual experience is perhaps a bit specious?

:-P

I am shooting 60 Mbps 4K with the X70 and it looks OUTSTANDING. I viewed a lot of my footage on a 4K monitor with a respected colleague here in Los Angeles and we did not observe said compression artifacting. (I own an F55 and have shot many 4K Raw and S-Log projects, so I have a very good basis for comparison.) The bottom line is not algorithms and equations, but how the images ultimately LOOK, and is your client and audience happy with them. All else is purely academic.

(I must remind everyone here: this is a $2,000 camera, plus the upgrade. If you want more firepower, it's available in the FS7, the F5, and the F55. But you're going to pay 4x, 8x, 15x as much, plus lenses. The X70 is absolutely amazing, especially for the price.)

Here is some of that 4K footage (obviously compressed for YouTube):

Sony PXW-X70 4K field test: Jody Eldred DP/Editor - YouTube

https://www.youtube.com/watch?v=vx3t...ature=youtu.be

Meanwhile back at the ranch... the Sony X70 shoots 'em up in 4K - YouTube

[David Heath]

Originally Posted by Ricky Sharp

Rough calculations taking into account that both sets of footage would be 8-bit 4:2:0

Your AVCHD 1080/50p @ 28 Mbps would have a compression ratio of 42:1
The UHD/25p @ 60 Mbps should have a compression ratio of 39:1

For the compression ratio, I took the number of bits required to store one second worth of the footage in 8-bit 4:2:0. Then divided by the recording bit rate.

Is the AVCHD footage at 50p really just using 28 Mbps though? I had thought it would be more like 35.

Sorry, but that argument is missing something vital - namely that going from 25p to 50p will almost certainly mean keeping the GOP-interval constant with respect to TIME - and hence the number of frames per GOP will change.

Numerical compression ratios don't tell the whole story in isolation - raise the number of frames in each GOP, and a higher (numerical) simple compression ratio will give equivalent quality per frame.

So it's likely that the time interval between I-frames will be 1/2 second in each case - which implies 12 frames per GOP for 25p, and 24 for 50p. Since the datarate in the difference frames is small compared to I-frames - and the number of I-frames/sec is 2 in each case - it follows the overall datarate won't need to increase very much between 25p and 50p for equivalent quality. Hence why "only" 28Mbs for 50p AVC-HD.

As for the ratios of HD:4K, then again (for equivalent quality) data rates don't scale up linearly with no of pixels. More pixels means more potential redundancy in the image for the compressor to exploit, so no, 4x as many pixels shouldn't mean 4x the datarate. (You can test the theory in Photoshop - start off with a high res image, then have a few downscaled versions, and compress them all to JPEG with the same quality setting in each case. I think you'll find that the compressed file sizes don't scale linearly with the image sizes.)