Dynamic Trickplay Source File Generation for Network DVR
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Solution Overview
Problem
Conventional dynamic trick play generation is inefficient due to reliance on a subset of I-frames, leading to poor disk I/O performance and inflexibility in handling multiple media streams, especially in RAID volumes and network DVR scenarios with real-time playback requirements.
Innovation Solution
Generating a trick play source file containing only I-frames and excluding audio and other non-essential data, which is pre-generated before viewer requests, allowing for dynamic creation of view files at various playback rates, reducing storage and CPU overhead, and optimizing disk I/O by writing a single trick play source file instead of multiple files.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional dynamic trick play generation references only a subset of I-frames from source MPEG content, then the system can generate trick play view files, but disk I/O efficiency deteriorates significantly especially on RAID volumes
Solution Approach 1:
The system performs preliminary filtering of the source MPEG bitstream during the trick play generation process, identifying and extracting only the necessary I-frames before writing them to the trick play view file. This preliminary action prevents reading unnecessary data from disk in the first place, thereby improving disk I/O efficiency while maintaining the ability to generate trick play files at various playback rates.
2Ease of manufacture
If simple cut-and-past operations on I-frames are performed to create trick play view streams, then the process is simple, but the resulting bitstreams become non-contiguous and non-compliant with MPEG standards
Solution Approach 1:
The system introduces an intermediary filtering and reassembly process between the source MPEG content and the trick play view file output. This intermediary stage performs intelligent packet filtering to extract only necessary I-frame packets, reassembles them in the correct sequence, and ensures proper MPEG bitstream compliance while maintaining relative simplicity in the overall generation process.
3Reliability
If real-time filtering is performed to exclude unwanted media streams, then compliant MPEG bitstreams can be produced, but significant overhead is added to the real-time processor
Solution Approach 1:
The system performs the filtering of unwanted media streams and reassembly of I-frame packets as a preliminary offline operation during trick play file generation, rather than as a real-time operation during playback. This shifts the processing overhead from the real-time playback path to the offline file generation path, eliminating real-time processor overhead while ensuring MPEG bitstream compliance.
4Adaptability or versatility
If all allowable trick play speeds are pre-generated as part of content ingest, then flexibility is reduced but storage space requirements increase for all trick play files
Solution Approach 1:
The system implements dynamic trick play file generation where trick play view files are created on-demand based on user playback rate requests rather than pre-generating all possible trick play speeds. The generation process dynamically selects and extracts only the I-frames necessary for the requested playback rate, providing full adaptability for any trick play speed while minimizing storage requirements by generating only what is needed.
Data Source
AI summary
At least one trickplay source file is generated from original media content. Trickplay view files for rendering particular trickplay view rates are then generated from the trickplay source file.