Videotelephony

Computer hardware

World Wide Web

Video capture

Real-time computing

Videoconferencing

Voice over IP

Quality of experience

Server

Operating system

Quality of service

The Internet

Telecommunications

Economics

Computer science

Protocol (science)

Video processing

Codec

Computer network

Alternative medicine

Mobile telephony

Operations management

Video quality

Mobile radio

Medicine

Metric (unit)

Telephony

Internet video

Software deployment

Session Initiation Protocol

Application layer

Pathology

Multimedia

Despite the pervasive use of real-time video telephony services, the users' quality of experience (QoE) remains unsatisfactory, especially over the mobile Internet. Previous work studied the problem via controlled experiments, while a systematic and in-depth investigation in the wild is still missing. To bridge the gap, we conduct a large-scale measurement campaign on \appname, an operational mobile video telephony service. Our measurement logs fine-grained performance metrics over 1 million video call sessions. Our analysis shows that the application-layer video codec and transport-layer protocols remain highly uncoordinated, which represents one major reason for the low QoE. We thus propose \name, a machine learning based framework to resolve the issue. Instead of blindly following the transport layer's estimation of network capacity, \name reviews historical logs of both layers, and extracts high-level features of codec/network dynamics, based on which it determines the highest bitrates for forthcoming video frames without incurring congestion. To attain the ability, we train \name with the aforementioned massive data traces using a custom-designed imitation learning algorithm, which enables \name to learn from past experience. We have implemented and incorporated \name into \appname. Our experiments show that \name outperforms state-of-the-art solutions, improving video quality while reducing stalling time by multi-folds under various practical scenarios.

Learning to Coordinate Video Codec with Transport Protocol for Mobile Video Telephony