Documentation / Gemini 330 series /
Metadata

Metadata

1. Brief Introduction

Metadata refers to data that provides information about other data. It acts like a descriptive label that helps to identify, manage, and use the actual data more effectively. Metadata can include a variety of details depending on the context:

  • Descriptive Metadata: This includes information like titles, authors, and keywords which help in discovering and identifying data. For example, the metadata of a book might include its title, author, publisher, and ISBN.
  • Structural Metadata: This indicates how a dataset is organized or how complex objects are put together. For instance, in a database, structural metadata would describe the tables, columns, relationships, and other structures used to organize data.
  • Administrative Metadata: This provides information to help manage a resource, like when and how it was created, file type, and access permissions. It might also include technical data necessary for managing digital resources such as file types or compression methods.
  • Reference Metadata: It provides information about the contents and quality of statistical data. This type is common in data-centric fields like statistics and data analysis, providing details on data sources, accuracy, and timeliness.

 

2. metadata of MIPI

In the context of MIPI, metadata can involve various types of information depending on the application. For example, in camera interfaces like MIPI CSI-2, metadata may include details about camera module parameters, resolution settings, frame rates, color spaces, white balance settings, sharpness, and chrominance. These details are crucial for properly configuring and utilizing the camera module.

Additionally, metadata might also pertain to control information related to data transmission, synchronization, error detection, and correction. This metadata is essential for ensuring the integrity and accuracy of data, especially in environments characterized by high-speed and low-power transmission.

On a broader scale, MIPI metadata may also involve system-level information, such as the connections between devices, data transmission rates, and power consumption budgets. This information aids in system-level design and optimization to ensure optimal performance and power efficiency of the entire system.

The specific definitions and implementations of metadata in the MIPI standards can vary based on different applications and requirements, and the information included in the metadata may differ among various device manufacturers.

 

3.Gemini 330 series metadata definition

Orbbec 3D cameras typically include components such as 2 IR modules, LDM, laser ranging module, and a color camera. Both the IR module and the color camera transmit data to the mainboard using the MIPI protocol, thus carrying metadata. Users can utilize the Orbbec SDK to parse this metadata and view it directly within the Orbbec Viewer to see the current data stream’s metadata information.

Taking the Gemini 335 as an example, the supported metadata includes the following content:

Table 3-1 Depth/IR metadata

Metadata Definition Range
timestamp exposure end timestamp /
sensor timestamp Exposure center timestamp-1/2 exposure time /
frame number current frame number /
auto exposure content of AE state [0,1]

0 for off, 1 for on

exposure content of exposure time 1~19900
gain content of exposure digital gain 16~248
ae roi left ROI AE start pixel X-axis 0~1278
ae roi top ROI AE start pixel Y-axis 0~798
ae roi right ROI AE end pixel X-axis 1~1279
ae roi bottom ROI AE end pixel Y-axis 1~799
exposure priority content of AE exposure priority state [0,1]
hdr sequence name User-defined content User-defined content
hdr sequence size HDR frame total number [0,2]

0 for off, 2 for on

hdr sequence index HDR frame sequence [0,1]

0 for first frame, 1 for second frame

laser power laser optical power [0,60,120,240,300,360]
laser power mode content of laser switch on or off [0,1]

0 for off, 1 for on

emitter mode Reserved [0,1,2,3]

0 – all emitters disabled.

1 – laser enabled.

2 – auto laser enabled (opt).

3 – LED enabled (opt).*

Gpio Input Data Reserved Reserved

 

Table 4-2 RGB metadata definition

Metadata Definition Range
timestamp 335: exposure start timestamp

335L: exposure start timestamp / exposure end timestamp

/
sensor timestamp 335: Exposure center timestamp

335L: Exposure center timestamp-1/2 exposure time

/
frame number current frame number /
auto exposure content of AE state [0,1]
exposure content of exposure time(us) [1,10000]
gain content of exposure digital gain [0,128]
auto white balance content of AWB state 0或1
white balance current AWB color temperature [2800,6500]
brightness current brightness [-64,64]
contrast contrast [0,100]
saturation saturation [0,100]
sharpness sharpness [0,100]
backlight compensation state of backlight compensation enable [0,1]

0 for off, 1 for on

hue hue [-180,180]
Gamma Gamma [100,500]
power line frequency anti-flicker state [50,60,disable,auto]
low light compensation state of low light compensation enable [0,1]

0 for off, 1 for on

manual white balance current AWB color temperature set manually [2800,6500]
actual frame rate frame rate set [5,10,15,30,60]
ae roi left ROI AE start pixel X-axis 335  [0,1918]

335L  [0,1278]

ae roi top ROI AE start pixel Y-axis 335 [0,1078]

335L [0,798]

ae roi right ROI AE end pixel X-axis 335 [1,1919]

335L [1,1279]

ae roi bottom

 

ROI AE end pixel Y-axis 335 [1,1079]

335L [1,799]

When using Orbbec 3D cameras on user platforms, metadata can be utilized to assess frame information, enabling advanced functions such as data correction, frame loss verification, and HDR (High Dynamic Range) fusion. This allows for enhanced accuracy and functionality in applications where precise imaging and data integrity are critical.

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