imagemechanic
imagemechanic

Here's a rough guide to those megabits per second.

Typical amounts of data that you might create, record, store, move around and transmit.

All numbers are Mb/s. All numbers are near enough for sport, as they say. Many codecs have alternative compression modes, storage devices are available in faster and slower/ cheaper versions. It's just to give you an idea.....

 

 

Terminology

 

Mb         mega bit =  1 million bits

MB         mega byte = 8 million bits

It would be really helpful if people stuck to bits when describing data rates, and Bytes when describing storage capacity, but they don’t, so be careful.

We also use ‘G’ for giga bit when describing data rates.

3G is approximately 3 gigabits per second etc.

 

 

Camera Codec

Old School:

Digital Betacam                               90

DVCam & HDV                                25

HDCAM                                         135

XDCAM                                      35-50

 

XAVC:

XAVC-L HD          25P                     50

XAVC-L 4K           25P                   100

XAVC-I  HD          25P                   100

XAVC-I 4K           25P            250/400

XAVC-I 4K           50P                    500

XAVC-I HD          180P                  600

 

RAW 4K 25P

RED Epic-W 8:1                            320

Sony XOCN LT                              406

Sony XOCN                                  688

Sony RAW                                  1000

Varicam LT V-RAW                      2200

Alexa Mini RAW 3.4K                   2300

 

Other useful references:

GoPro HD 25P                                 30

GoPro 4K 25P                                  60

Amira ProRes HD 4444                   312

 

 

 

 

What you start with:

An HD studio or OB production at 25i     1500

UHD studio or OB production               12000

RAW 25P output from a typical 4K camera                                                           4000

 

And what you end up with:

Transmission to your screen via IP, Satellite or Freeview:

HD                                                     4 to 8

UHD                                               10 to 25



 

Interfaces

Just because you have a fast connection doesn’t mean your source can deliver or your destination can write at that speed:

USB 2.0                                           480

USB 3.0                            (6G)      5000

SATA 3.0                           (6G)      6000

USB 3.1                          (10G)     10000

Thunderbolt 2                  (10G)     10000

Thunderbolt 3                  (40G)     40000

SDSDI                                               270

HDSDI    25P or 25i           (1.5G)    1500

HDSDI    50P                      (3G)      3000

UHD       25P or 25i             (6G)      6000

UHD       50P                     (12G)    12000

 

 

Media Write Speeds

Figures are typical maximum for a good quality device. You need plenty of headroom though, for when your media gets a bit tired.

HDD                        100

SSD                        400

SDXC U3                2000

C-FAST 2                3000      

XQD                       3200

SxS                        3200

AXS                        4800


 

Record Time

What you really need to know of course, is how long can I record for a given capacity card or drive.

Divide your Mbps by two.

That’s the number of GB you will need for an hour.

e.g. recording at 100 Mbps

Divide by two; that’s 50GB an hour.

Your 64GB card will last about an hour and a quarter. It's easy when you know your Mbps !

 

Mbps/2 = GB/ hr

 

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© Neil Thompson