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Strata: Layered Coding for Scalable Visual Communication
Strata: Layered Coding for Scalable Visual Communication
You may have seen these…
You may have seen these…
Smartphone cameras as “receivers”
Smartphone cameras as “receivers”
… everywhere
… everywhere
Existing codes: All or nothing
Existing codes: All or nothing
Multi-resolution information display
Multi-resolution information display
Diverse camera hardware
Diverse camera hardware
Capture distance vs resolution
Capture distance vs resolution
Our goal
Our goal
In the rest of the talk…
In the rest of the talk…
Undersampled channel
Undersampled channel
Spatial undersampling
Spatial undersampling
Spatial undersampling
Spatial undersampling
Color mixing experiment
Color mixing experiment
Color mixing results
Color mixing results
Color mixing results
Color mixing results
Color mixing results
Color mixing results
Color mixing results
Color mixing results
Strata Design
Strata Design
Toy example
Toy example
A simple SNR (like) model
A simple SNR (like) model
A simple SNR (like) model
A simple SNR (like) model
Basic design
Basic design
Harnessing additional bits
Harnessing additional bits
Example 2-layer code
Example 2-layer code
Recursively adding layers
Recursively adding layers
Harnessing more bits
Harnessing more bits
Harnessing more bits
Harnessing more bits
Choice of parameters
Choice of parameters
Decoding
Decoding
Decoding
Decoding
Decoding
Decoding
Strata performance
Strata performance
Example Strata image
Example Strata image
Decoder implementation
Decoder implementation
Performance metric
Performance metric
Performance (spatial)
Performance (spatial)
Performance (spatial)
Performance (spatial)
Strata vs Single-layer code
Strata vs Single-layer code
Strata vs Single-layer code
Strata vs Single-layer code
Strata vs Single-layer code
Strata vs Single-layer code
Other comparison results
Other comparison results
Related work
Related work
Conclusion
Conclusion
Thank you
Thank you

Презентация: «Strata: Layered Coding for Scalable Visual Communication». Автор: Wenjun Hu. Файл: «Strata: Layered Coding for Scalable Visual Communication.ppt». Размер zip-архива: 4840 КБ.

Strata: Layered Coding for Scalable Visual Communication

содержание презентации «Strata: Layered Coding for Scalable Visual Communication.ppt»
СлайдТекст
1 Strata: Layered Coding for Scalable Visual Communication

Strata: Layered Coding for Scalable Visual Communication

Wenjun Hu Jingshu Mao Zihui Huang Yiqing Xue Junfeng She Kaigui Bian Guobin (Jacky) Shen

2 You may have seen these…

You may have seen these…

3 Smartphone cameras as “receivers”

Smartphone cameras as “receivers”

4 … everywhere

… everywhere

5 Existing codes: All or nothing

Existing codes: All or nothing

Camera view

Minimum resolution needed

6 Multi-resolution information display

Multi-resolution information display

7 Diverse camera hardware

Diverse camera hardware

Lumia 1020 ~38MP, 30fps

Nexus 5 8MP, 30fps

iPhone 4 5MP, 30fps

iPhone 5s 8MP, 120fps

8 Capture distance vs resolution

Capture distance vs resolution

9 Our goal

Our goal

Multi-resolution encoding and decoding Analogous to HM and SVC for scalable channel/source coding Decoding performance scales with receiver capability and channel condition

10 In the rest of the talk…

In the rest of the talk…

Undersampled channel Strata design Strata performance Focus on spatial, analogous for temporal See paper for temporal mixing, code design, and performance results

11 Undersampled channel

Undersampled channel

12 Spatial undersampling

Spatial undersampling

Original image

Captured at 28m , enlarged

13 Spatial undersampling

Spatial undersampling

In theory, linear mixing of pixel colors In practice, messier… (Auto-)Focus, exposure, contrast Noise at block edges …

14 Color mixing experiment

Color mixing experiment

Patterns of alternating squares

15 Color mixing results

Color mixing results

16 Color mixing results

Color mixing results

For the same distance, close to linear color mixing

17 Color mixing results

Color mixing results

Darker when further away White is better preserved

18 Color mixing results

Color mixing results

Less grayscale difference if minimal contrast

19 Strata Design

Strata Design

20 Toy example

Toy example

2 layers Black overall Also small blocks Small white blocks are interference

21 A simple SNR (like) model

A simple SNR (like) model

Signal = # of small blocks of the intended color Noise = # of small blocks of other colors Both noise and interference This actually reflects color mixing weights for monochrome codes

22 A simple SNR (like) model

A simple SNR (like) model

If SNR > 1, the overall block carries at least 1 bit of information Its color can be determined Key: Control noise/interference “Reserve” the color of some blocks

23 Basic design

Basic design

2-layer structure, with reserved block

Reserved block

Base layer block

Enhancement layer block

Ensures black majority Contiguous to mitigate issues in color mixing

24 Harnessing additional bits

Harnessing additional bits

Bits from reserved block shape

2 bits from 4 different positions

25 Example 2-layer code

Example 2-layer code

Base layer block

Enhancement layer block

26 Recursively adding layers

Recursively adding layers

Divide each enhancement block further Follow the same rule otherwise

Reserved block

(In)Dependency between layers: structural, but not the information encoded

Base layer (2nd layer) block

Enhancement layer (3rd layer) block

27 Harnessing more bits

Harnessing more bits

Adding smaller (third-layer) blocks in the reserved block

28 Harnessing more bits

Harnessing more bits

Doubles the third-layer capacity Can further add fourth-layer blocks

29 Choice of parameters

Choice of parameters

Reserved block size Efficiency vs accuracy tradeoff Need ? when not knowing input statistics “Branching factor” Control of granularity 16 offers a good tradeoff Details in the paper

30 Decoding

Decoding

31 Decoding

Decoding

Divide into blocks Start with Layer 1 Determine per-block colors 11 blacks, 5 whites Majority gives overall block color (black)

32 Decoding

Decoding

Continue with finer blocks Stop if can’t divide further

33 Strata performance

Strata performance

34 Example Strata image

Example Strata image

20cm x 20cm on screen, no error correction

35 Decoder implementation

Decoder implementation

Online Android app & Offline version

Multi-level decoded info

Strata test display

36 Performance metric

Performance metric

Goal recap: The amount of information decoded scales with capture resolution/rate Metric: decodable bit/layer count

37 Performance (spatial)

Performance (spatial)

38 Performance (spatial)

Performance (spatial)

39 Strata vs Single-layer code

Strata vs Single-layer code

40 Strata vs Single-layer code

Strata vs Single-layer code

41 Strata vs Single-layer code

Strata vs Single-layer code

Strata balances capacity and supported distance

42 Other comparison results

Other comparison results

Strata vs frequency domain encoding Strata vs multi-level grayscales Strata vs group of codes Details in the paper

43 Related work

Related work

Temporal barcode design (inter-frame) Unsynchronized 4D Barcodes Spatial barcode design (per-frame layout) PixNet, COBRA Visual tags Hierarchical coding on LED arrays Other work on visible light communications E.g., Visual MIMO

44 Conclusion

Conclusion

Diverse screen/surface-camera channels Hardware diversity Capture conditions vary Strata: Layered coding for scalability The amount of information decoded scales with diverse channel conditions

45 Thank you

Thank you

Questions?

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