Blog
The latest news from Google AI
Improving Holistic Scene Understanding with Panoptic-DeepLab
Tuesday, July 21, 2020
Posted by Bowen Cheng, Student Researcher and Liang-Chieh Chen, Research Scientist, Google Research
Real-world computer vision applications, such as self-driving cars and robotics, rely on two core tasks —
instance segmentation
and
semantic segmentation
. Instance segmentation identifies the class and extent of individual “things” in an image (i.e., countable objects such as people, animals, cars, etc.) and assigns unique identifiers to each (e.g., car_1 and car_2). This is complemented by
semantic segmentation
, which labels all pixels in an image, including the “things” that are present as well as the surrounding “stuff” (e.g., amorphous regions of similar texture or material, such as grass, sky or road). This latter task, however, does not differentiate between pixels of the same class that belong to different
instances
of that class.
Panoptic segmentation
represents the unification of these two approaches with the goal of assigning a unique value to every pixel in an image that encodes both semantic label and instance ID. Most existing panoptic segmentation algorithms are based on
Mask R-CNN
, which treats semantic and instance segmentation separately. The instance segmentation step identifies objects in an image, but it often produces object instance masks that overlap one another. To settle the conflict between overlapping instance masks, one commonly employs an heuristic that resolves the discrepancy either based on the mask with a higher confidence score or by use of a pre-defined pairwise relationship between categories (e.g., a tie should always be worn on a person’s front). Additionally, the discrepancies between semantic and instance segmentation results are sorted out by favoring the instance predictions. While these methods generally produce good results, they also introduce heavy latency, which makes it challenging to apply them in real-time applications.
Driven by the need of a real-time panoptic segmentation model, we propose “
Panoptic-DeepLab: a simple, fast and strong system for panoptic segmentation
”, accepted to
CVPR 2020
. In this work, we extend the commonly used modern semantic segmentation model,
DeepLab
, to perform panoptic segmentation using only a small number of additional parameters with the addition of marginal computation overhead. The resulting model, Panoptic-DeepLab, produces semantic and instance segmentation in parallel and without overlap, avoiding the need for the manually designed heuristics adopted by other methods. Additionally, we develop a computationally efficient operation that merges the semantic and instance segmentation results, enabling near real-time end-to-end panoptic segmentation prediction. Unlike methods based on Mask R-CNN, Panoptic-DeepLab does not generate
bounding box predictions
and requires only three loss functions during training, significantly fewer than current state-of-the-art methods, such as
UPSNet
, which can have up to eight. Finally, Panoptic-DeepLab has demonstrated state-of-the-art performance on several academic datasets.
Panoptic segmentation results obtained by Panoptic-DeepLab.
Left:
Video frames used as input to the panoptic segmentation model.
Right:
Results overlaid on video frames. Each object instance has a unique label, e.g., car_1, car_2, etc.
Overview
Panoptic-DeepLab is simple both conceptually and architecturally. At a high-level, it predicts three outputs. The first is semantic segmentation, in which it assigns a semantic class (e.g., car or grass) to each pixel. However, it does not differentiate between multiple instances of the same class. So, for example, if one car is partly behind another, the pixels associated with both would have the same associated class and would be indistinguishable from one another. This can be addressed by the second two outputs from the model: a center-of-mass prediction for each instance and instance center regression, where the model learns to regress each instance pixel to its center of mass. This latter step ensures that the model associates pixels of a given class to the appropriate instance. The class-agnostic instance segmentation, obtained by grouping predicted foreground pixels to their closest predicted instance centers, is then fused with semantic segmentation by majority-vote rule to generate the final panoptic segmentation.
Overview of Panoptic-DeepLab. Semantic segmentation associates pixels in the image with general classes, while the class-agnostic instance segmentation step identifies the pixels associated with an individual object, regardless of the class. Taken together one gets the final panoptic segmentation image.
Neural Network Design
Panoptic-DeepLab consists of four components: (1) an encoder backbone pre-trained on
ImageNet
, shared by both the semantic segmentation and instance segmentation branches of the architecture; (2)
atrous spatial pyramid pooling
(ASPP) modules, similar to that used by
DeepLab
, which are deployed independently in each branch in order to perform segmentation at a range of spatial scales; (3) similarly decoupled
decoder modules
specific to each segmentation task; and (4) task-specific prediction heads.
The encoder backbone (1), which has been pre-trained on ImageNet, extracts feature maps that are shared by both the semantic segmentation and instance segmentation branches of the architecture. Typically, the feature map is generated by the backbone model using a standard convolution, which reduces the resolution of the output map to 1/32nd that of the input image and is too coarse for accurate image segmentation. In order to preserve the details of object boundaries, we instead employ
atrous convolution
, which better retains important features like edges, to generate a feature map with a resolution of 1/16th the original. This is then followed by two ASPP modules (2), one for each branch, which captures multi-scale information for segmentation.
The light-weight decoder modules (3) follow those used in the most recent DeepLab version (
DeepLabV3+
), but with two modifications. First, we reintroduce an additional low-level feature map (1/8th scale) to the decoder, which helps to preserve spatial information from the original image (e.g., object boundaries) that can be significantly degraded in the final feature map output by the backbone. Second, instead of using the typical 3 × 3 kernel, the decoder employs a 5 × 5 depthwise-separable convolution, which yields somewhat better performance at only a minimal cost in additional overhead.
The two prediction heads (4) are tailored to their task. The semantic segmentation head employs a weighted version of the standard bootstrapped cross entropy loss function, which weights each pixel differently and has proven to be more effective for segmentation of small-scale objects. The instance segmentation head is trained to predict the offsets between the center of mass of an object instance and the surrounding pixels, without knowledge of the object class, forming the class-agnostic instance masks.
Results
To demonstrate the effectiveness of Panoptic-DeepLab, we conduct experiments on three popular academic datasets,
Cityscapes
,
Mapillary Vistas
, and
COCO
datasets. With a simple architecture, Panoptic-DeepLab ranks first in
Cityscapes
for all three tasks (semantic, instance and panoptic segmentation) without any task-specific fine-tuning. Additionally, Panoptic-DeepLab won the
Best Result
,
Best Paper
, and
Most Innovative
awards on the
Mapillary Panoptic Segmentation track
at
ICCV 2019 Joint COCO and Mapillary Recognition Challenge Workshop
. It outperforms the winner of 2018 by a healthy margin of 1.5%. Finally, Panoptic-DeepLab sets new state-of-the-art bottom-up (i.e., box-free) panoptic segmentation results on the
COCO
dataset, and is also comparable to other methods based on Mask R-CNN.
Accuracy (PQ) vs. Speed (GPU inference time) across three datasets.
Conclusion
With a simple architecture and only three training loss functions, Panoptic-DeepLab achieves state-of-the-art performance while being faster than other methods based on
Mask R-CNN
. To summarize, we develop the first single-shot panoptic segmentation model that attains state-of-the-art performance on several public benchmarks, and delivers near real time end-to-end inference speed. We hope our simple and effective Panoptic-DeepLab could establish a solid baseline and further benefit the research community.
Acknowledgements
We would like to thank the support and valuable discussions with Maxwell D. Collins, Yukun Zhu, Ting Liu, Thomas S. Huang, Hartwig Adam, Florian Schroff as well as the Google Mobile Vision team.
Labels
accessibility
ACL
ACM
Acoustic Modeling
Adaptive Data Analysis
ads
adsense
adwords
Africa
AI
AI for Social Good
Algorithms
Android
Android Wear
API
App Engine
App Inventor
April Fools
Art
Audio
Augmented Reality
Australia
Automatic Speech Recognition
AutoML
Awards
BigQuery
Cantonese
Chemistry
China
Chrome
Cloud Computing
Collaboration
Compression
Computational Imaging
Computational Photography
Computer Science
Computer Vision
conference
conferences
Conservation
correlate
Course Builder
crowd-sourcing
CVPR
Data Center
Data Discovery
data science
datasets
Deep Learning
DeepDream
DeepMind
distributed systems
Diversity
Earth Engine
economics
Education
Electronic Commerce and Algorithms
electronics
EMEA
EMNLP
Encryption
entities
Entity Salience
Environment
Europe
Exacycle
Expander
Faculty Institute
Faculty Summit
Flu Trends
Fusion Tables
gamification
Gboard
Gmail
Google Accelerated Science
Google Books
Google Brain
Google Cloud Platform
Google Docs
Google Drive
Google Genomics
Google Maps
Google Photos
Google Play Apps
Google Science Fair
Google Sheets
Google Translate
Google Trips
Google Voice Search
Google+
Government
grants
Graph
Graph Mining
Hardware
HCI
Health
High Dynamic Range Imaging
ICCV
ICLR
ICML
ICSE
Image Annotation
Image Classification
Image Processing
Inbox
India
Information Retrieval
internationalization
Internet of Things
Interspeech
IPython
Journalism
jsm
jsm2011
K-12
Kaggle
KDD
Keyboard Input
Klingon
Korean
Labs
Linear Optimization
localization
Low-Light Photography
Machine Hearing
Machine Intelligence
Machine Learning
Machine Perception
Machine Translation
Magenta
MapReduce
market algorithms
Market Research
Mixed Reality
ML
ML Fairness
MOOC
Moore's Law
Multimodal Learning
NAACL
Natural Language Processing
Natural Language Understanding
Network Management
Networks
Neural Networks
NeurIPS
Nexus
Ngram
NIPS
NLP
On-device Learning
open source
operating systems
Optical Character Recognition
optimization
osdi
osdi10
patents
Peer Review
ph.d. fellowship
PhD Fellowship
PhotoScan
Physics
PiLab
Pixel
Policy
Professional Development
Proposals
Public Data Explorer
publication
Publications
Quantum AI
Quantum Computing
Recommender Systems
Reinforcement Learning
renewable energy
Research
Research Awards
resource optimization
Robotics
schema.org
Search
search ads
Security and Privacy
Self-Supervised Learning
Semantic Models
Semi-supervised Learning
SIGCOMM
SIGMOD
Site Reliability Engineering
Social Networks
Software
Sound Search
Speech
Speech Recognition
statistics
Structured Data
Style Transfer
Supervised Learning
Systems
TensorBoard
TensorFlow
TPU
Translate
trends
TTS
TV
UI
University Relations
UNIX
Unsupervised Learning
User Experience
video
Video Analysis
Virtual Reality
Vision Research
Visiting Faculty
Visualization
VLDB
Voice Search
Wiki
wikipedia
WWW
Year in Review
YouTube
Archive
2021
Apr
Mar
Feb
Jan
2020
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2019
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2018
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2017
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2016
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2015
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2014
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2013
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2012
Dec
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2011
Dec
Nov
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2010
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2009
Dec
Nov
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
2008
Dec
Nov
Oct
Sep
Jul
May
Apr
Mar
Feb
2007
Oct
Sep
Aug
Jul
Jun
Feb
2006
Dec
Nov
Sep
Aug
Jul
Jun
Apr
Mar
Feb
Feed
Follow @googleai
Give us feedback in our
Product Forums
.
