GOP Structure I-Frame Positioning for Digital TV Entry
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Solution Overview
Problem
In digital television systems, the unpredictable positioning of I-frames in the GOP structure leads to delays in program entry or changes, resulting in artifacts and noisy pictures due to insufficient image information, especially when switching between programs.
Innovation Solution
The method involves determining the transmission time of each second data frame based on parameters like transmission start and duration, converting P- or B-frames to I-frames at the start of data frames, and reducing data volume by adjusting the quantization of image elements or extending the GOP duration, ensuring that I-frames are transmitted at the start of data frames, thus minimizing delays and maintaining picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If P-frames and B-frames are used in the GOP structure to reduce data volume, then transmission efficiency is improved, but delays occur during program changes or entry because I-frames are not positioned at the start of data frames
Solution Approach 1:
The patent applies preliminary action by proactively positioning I-frames at the start of data frames before transmission occurs. The source encoder is configured to ensure that I-frames are placed at the beginning of their respective data frames, so that when a program change or entry occurs, the decoder immediately receives complete image data without having to wait for subsequent I-frames. This advance preparation eliminates delays while maintaining the efficiency benefits of P- and B-frames for regular transmission.
Solution Approach 2:
The patent segments the data frame structure to separate the positioning requirement for I-frames from the compression strategy for P- and B-frames. By dividing the GOP structure into distinct segments where I-frames are anchored at data frame starts while P- and B-frames follow in compressed form, the system achieves both rapid program entry (through segmented I-frame positioning) and transmission efficiency (through compressed P- and B-frames).
2Reliability
If I-frames are transmitted at the start of data frames to minimize program entry delays, then picture quality is improved, but data volume increases
Solution Approach 1:
The patent applies local quality by applying different frame types to different temporal locations within the transmission stream. Specifically, I-frames are used at the start of data frames where high picture quality is critical for program entry, while P-frames and B-frames are used for subsequent frames where compression efficiency is more important. This localized application of full I-frame quality only where necessary minimizes overall data volume while ensuring picture quality reliability when needed.
Solution Approach 2:
The patent changes the parameter of frame type selection based on temporal position in the transmission stream. By dynamically selecting I-frames at data frame starts and P- or B-frames elsewhere, the system adjusts the quality-compression parameter according to transmission context, achieving acceptable picture quality with reduced total data volume compared to using only I-frames throughout.
3Stability of the object's composition
If the GOP structure is adjusted to align with fixed-length ATSC-M/H data frames, then transmission synchronization is improved, but the number of packets becomes non-integer and unpredictable
Solution Approach 1:
The patent applies self-service by enabling the source encoder to autonomously determine the positioning of I-frames within the fixed-length ATSC-M/H data frame structure. The source encoder monitors its own output and automatically adjusts GOP structure parameters to ensure I-frames align with data frame starts, eliminating the need for external synchronization control and simplifying the overall system architecture while maintaining stable transmission synchronization.
Solution Approach 2:
The patent introduces dynamics by allowing the GOP structure parameters (such as the number of P- and B-frames between I-frames) to be adjusted dynamically based on the fixed data frame length requirement. This dynamic adaptation enables the system to maintain a consistent number of packets per data frame while still achieving proper I-frame positioning, thereby simplifying packet structure rather than complicating it.
Data Source
AI summary
A transport data stream is generated by generating a data stream of successive second data frames with a GOP structure for each program containing image data of an image of an image sequence recorded digitally and belonging to the respective program by a source encoder. The transmission start, transmission period and transmission time are determined. At the start of first data frames, second data frames realized as P-frames or B-frames to be transmitted are replaced by second data frames realized as I-frames in each of the data streams belonging to a program and each first data frame of the transport data stream is packed with second data frames of data streams belonging in each case to one program whose transmission time fits the transmission start and the transmission period of the respective first data frame by means of a multiplexer.