Transcoded Intra-Coded Images for Trick Play
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Solution Overview
Problem
Existing digital video recorders face challenges in implementing fast forward and fast reverse playback for compressed video streams, particularly with H.264 format, due to high computational complexity and the need for expensive video processors, while prior solutions like low resolution recording require excessive storage.
Innovation Solution
Transcoding non-intra coded images into intra-coded images during normal playback, storing these transcoded images, and using a sliding image sequence window to manage storage, allowing for efficient decoding during trick mode playback with lower complexity video processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If inter-coded pictures (P and B pictures) are used for compression, then storage space and bandwidth are reduced, but decoding complexity increases significantly for trick mode playback
Solution Approach 1:
The system performs preliminary transcoding of selected P and B pictures into I pictures during normal playback. These transcoded I pictures are stored in advance in a buffer, so when trick mode playback is requested, the decoder only needs to decode I pictures which have simpler decoding requirements, thus reducing the decoding complexity during trick mode operations.
2Ease of operation
If more video images are decoded for fast forward/reverse playback, then trick mode playback becomes possible, but processing speed requirements increase
Solution Approach 1:
The system pre-decodes and stores selected pictures as I pictures during normal playback operations. This preliminary action ensures that when fast forward or fast reverse is requested, the pre-decoded I pictures are already available in the buffer, eliminating the need for high-speed real-time decoding during trick mode playback.
Solution Approach 2:
The system selectively transcodes only certain P and B pictures (those likely to be needed for trick mode playback) into I pictures, rather than converting all pictures. This local quality approach optimizes the balance between having enough pre-decoded frames for smooth trick mode playback and minimizing the additional processing burden during normal playback.
3Quantity of substance
If H.264 compression format is used, then compression efficiency is improved, but decoding complexity for trick play increases compared to MPEG-2
Solution Approach 1:
The system performs preliminary transcoding of H.264 compressed video, converting selected P and B slices into I slices during normal playback. This advance preparation reduces the computational burden during trick mode playback, making H.264 trick play feasible without requiring excessively complex real-time decoding capabilities.
Data Source
AI summary
A method and apparatus are provided for facilitating processing of images contained in an encoded video stream wherein a plurality of non-intra coded images are transcoded into intra-coded images (I-images). The transcoded I-images are then used to facilitate trick mode playback, such as reverse playback, fast reverse playback or fast forward playback. In addition, an image sequence window is defined and transcoded I-images which fall outside of the image sequence window are deleted from a memory.