Deferred License Retrieval for Streaming Media Playback

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Solution Overview

Problem

Digital media content distribution systems experience delays in playback initiation due to the time required for content players to request and receive protected digital media content and associated licenses, leading to a perceived delay before playback can begin.

Innovation Solution

Implementing fast start streams that are unprotected and encoded at a lower bit rate, allowing playback to start before the license and protected version of the content is received, with the streaming server generating these streams either precomputed or on-the-fly to minimize startup time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the content player waits to receive the license and protected digital media content before starting playback, then the digital rights management protection is maintained, but the perceived delay before playback begins increases

Engineering Contradiction:

Improvedigital rights management protectionVSAvoidperceived delay before playback

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary actions by downloading and buffering unprotected fast-start streams before the license is acquired. The content player prepares playback components (video frames, audio samples) in advance using unprotected data, so that when the license arrives, playback can begin immediately without waiting for protected content download.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The media content is segmented into two distinct streams: unprotected fast-start streams for immediate playback, and protected streams for full-quality playback. This segmentation allows the system to separate the function of quick startup from the function of protected content delivery, resolving the contradiction between speed and security.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the content player downloads protected digital media content at full bit rate, then the playback quality is maintained, but the download time and perceived delay increase

Engineering Contradiction:

Improveplayback qualityVSAvoiddownload time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

Different quality levels are applied to different portions of the content delivery process. Fast-start streams use lower bit rates and simpler encoding for quick delivery, while protected streams use full bit rates for high-quality playback. This local quality differentiation allows the system to optimize for speed when needed and for quality when needed.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system changes encoding parameters (bit rate, compression level, GOP structure) between fast-start streams and protected streams. Fast-start streams use aggressive compression and lower bit rates to enable rapid download, while protected streams use optimal encoding parameters for high quality. This parameter change resolves the contradiction between download speed and playback quality.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the content player requires a full GOP to be received before decoding video data, then the video synchronization is maintained, but the startup delay increases

Engineering Contradiction:

Improvevideo synchronizationVSAvoidstartup delay

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The system performs preliminary decoding of video data from fast-start streams before the license is acquired. By pre-decoding video frames and preparing them for display, the system eliminates the need to wait for a complete GOP from protected streams, reducing startup delay while maintaining synchronization through timestamp management.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of waiting for complete GOP structures from protected streams before playback, the system inverts the approach by using incomplete, partially decoded fast-start streams for initial playback. This inversion allows playback to start before all necessary data structures are available, resolving the contradiction between synchronization requirements and startup speed.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP2724282B1Fast start of streaming digital media playback with deferred license retrieval

Publication Date: 2020.03.18 NETFLIX INC

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AI summary

One embodiment of the present invention sets forth a technique for deferring license retrieval when streaming digital media content. The perceived delay between the time a user selects the protected digital media content to when playback of the protected digital media content begins is reduced because retrieval and playback of an unprotected version of a portion of the digital media content starts before the license and protected version of the digital media content is received. The unprotected version includes fast start streams of audio and video data that may encoded at a lower bit rate than the protected version in order to quickly transfer the fast start streams from the content server to the playback device.