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

[David Heath]

Originally Posted by Cliff Totten

I think we often tend to think of XAVC as a "special" CODEC. It's really not. It's a "special container" format that employs MPEG's generic h.264 CODEC library.

Cliff, this has already been covered. There is no such thing as a single "generic h.264 CODEC library" - it's something that's constantly evolving. But in a way that ensures backwards compatibility. So that the latest DECODER will be able to decode H264 from an early encoder - but an early decoder may not be able to decode H264 from a modern coder.

And because XAVC is a new(ish) implementation of H264, expect it to able to employ the latest "tricks" - but on the flip side don't expect older decoders to be happy with it. That means much more than just a container difference.

And all this is quite apart from all coders of nominally the same codec performing equally. An implementation (such as XAVC) may imply all the "tricks" that MAY be used - it doesn't mean that all coders necessarily will use them all.

[Cliff Totten]

Yup, you are right. There are different decoders out there from all the years of H.264's existence.

For instance, if you have a 7 year old, fully H.264 AVC compliant decoder that can handle up to level 4.2 and you try to feed it H.264, UHD level 5.2 it probably wont be able to handle it.

Why? Although, this 7 year old dcecoder could easily have all the tools and calculations needed for decoding the newer file, it likely would crash on the bit rate, frame rate and/or frame size increases. That is the part that will freak out the decoder. It's not the "high profile" tools or CABAC or loop deblocking or any of the other 100 compression options.

A 7 year old "hardware" decoder is guaranteed to crash. A 7 year old "software" decoder probably too but who know's maybe not, if it's running with a modern CPU and is not inspecting that metadata too hard.

It's hard to believe but even the highest level 5.2 (XAVC) limitation is already 4+ years old!!

Remember, the MPEG Part 10 (AVC) tool sets and compression library is 10 years old now. The "compression" itself is the same,...what has changed over all the years is the "level" restrictions. The same 10 year old compression tools are allowed to operate in bigger and bigger parameters with every level increase. (yeah,..3d packing was added, color space changes...stuff like that has been increased over the years)

Remember, Sony cannot add a new awesome calculation of their own for entropy encoding to XAVC. Add one single thing that is "outside" the decoder library and a "new" codec is born. (it will no longer be H.264 AVC)

H.264 AVC is "evolving" as you say...because of level limitation increases. What is not "evolving" is the compression tool sets and decoding library. That was "locked-in" when h.264 AVC was ratified.

The H.264 compression tool sets and calculations have evolved in the form of the next new codec. H.265 HEVC. This new codec takes h.264 AVC and DOES add new calculations and tools into it. But this is why we must call it a new CODEC and not just H.264 "turbo" or H.264 "plus" or h.264 level 6....it breaks H.264's tool book!

[Jack Zhang]

Just bumping this thread up to say someone in our community is now using 60mbps 4K30p in ENG news gathering, full of police strobe lights and numerous things that will cause the codec to literally break up. Keep an eye on Paul Anderegg's ENG work to see how well 60mbps holds up for news.

Also, it's been a few months, where was the promised scientific test? The best test would be crashing waves, as even on the Panasonic TM700 back in the day, I could see the codec break up on the details of the waves.

[Cliff Totten]

I got an offer for my AX100 and sold it before I could do the side by side high motion codec test. :-(

Oh well. Maybe somebody has an AX100 that they could do this with? After months of working with bot the AX100 and the X70, (I use the x70 allot today in 4k) I can say that both 100Mbp/s and 60Mbp/s look pretty similar under light to medium complexity scenes. Only the heaviest random movement like a flock of birds taking flight or intense ocean waves will brake the 60Mbp/s codec. You CAN break 60 but it really needs allot of crazy motion to do it.

I really wish that Sony would add the 100Mbp/s option. It sucks when Sony's consumer division adds 100Mbp/s all over the place in their cheaper models and Sony Pro is being stingy with it on this XDCAM model.

[Paul Anderegg]

Jack, here are a few test clips from a fire I shot this morning.

YouTube (Short URL)

[Peter Wright]

Wow Paul, that's some impressive footage there, well done - how high did you put the gain?

[Paul Anderegg]

As high as necessary, probably no higher than 27 for the grainiest. In an action environment, the stupid 3 button one dial exposure controls are a huge disadvantage. I had to click in full auto a few times just to get the shots. I still think my X180 looks better in 720p60 than the X70 does in 4K. The X70 colors are just all wrong most of the time. Accurate colors can make standard def look amazing.

Since my 4K conversion, red LED fire truck lights are now ellow instead of orange...........ugh, 4:2:0.

Paul

[Craig Seeman]

Noting that the just announced Sony FS5 which lists for about $6000 with lens at B&H shoots 4k 8 bit 4:2:0 at 100mbps.