Null Packet Timing Adjustment for Digital TV Stream Multiplexing
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Solution Overview
Problem
In digital television broadcasting, the degradation of video and audio quality occurs due to inconsistent packet arrival times at the decoding unit, caused by the removal of regular null packets during multiplexing, leading to timing issues and errors in reproduction.
Innovation Solution
A receiving device and method that inserts null packets with time information into empty spaces in the multiplexed stream, ensuring proper timing adjustments are made to maintain consistent packet arrival times, using a demodulation unit, packet selection units, a multiplexer, demultiplexer, and output timing adjustment unit to generate and decode service streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regular null packets are discarded to suppress the overall bit rate of the multiplexed TS, then the bit rate is reduced, but the arrival time of packets at the decoding unit becomes inconsistent
Solution Approach 1:
The system performs preliminary action by inserting null packets with time information (PCR values) before multiplexing occurs. These null packets are generated in advance with correct timing information, ensuring that when packets are later multiplexed and transmitted, the decoding unit receives packets at consistent time intervals. This preliminary insertion of timing-correct null packets prevents timing disruption before it occurs.
Solution Approach 2:
Null packets with time information serve as intermediaries between the multiplexing process and the decoding unit. These intermediary packets carry PCR values that act as timing references, mediating the transmission between multiple service streams and the decoding unit. The null packets buffer and regulate the flow of packets, ensuring consistent timing delivery to the decoder even when other packets are multiplexed in between.
2Adaptability or versatility
If a larger number of packets from other TSs are inserted into null packet spaces, then more services can be multiplexed, but the original number of null packets is not ensured and timing is disrupted
Solution Approach 1:
The system applies local quality by differentiating between regular null packets and null packets with time information. Regular null packets are simple placeholders, while null packets with time information contain embedded PCR values that provide timing references. This local differentiation ensures that specific null packets serving timing functions maintain their timing-correct nature, while other null packets can be replaced with service packets for multiplexing purposes.
Solution Approach 2:
The system changes the parameter of null packets by embedding time information (PCR values) within them. This parameter change transforms ordinary null packets into timing-reference carriers. The PCR values embedded in these null packets provide the decoding unit with timing information needed to synchronize playback, allowing the system to maintain timing accuracy even as the composition and number of packets changes due to multiplexing operations.
3Ease of operation
If packets are transmitted without ensuring constant time intervals, then transmission flexibility increases, but decoding quality degrades due to time axis failure
Solution Approach 1:
The system implements feedback by embedding PCR (Program Clock Reference) values in null packets that are transmitted to the decoding unit. These PCR values provide timing feedback information that allows the decoding unit to synchronize its internal clock with the transmitted stream. This feedback mechanism ensures that even with flexible packet transmission and multiplexing, the decoder can maintain accurate timing and reproduce video and audio without quality degradation.
Data Source
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AI summary
The present disclosure relates to a data processing device, a receiving device, a data processing method, and a program capable of suppressing degradation in quality in a case of reproducing data. Packet selection units select, from a multiplexed stream obtained by multiplexing a plurality of service streams, packets configuring respective service streams and generate one service stream. Insertion units insert null packets with time information, in which predetermined time information has been given to payloads, to spaces which have become empty when a predetermined number of the packet selection units generate the one service stream. Thereafter, in the streams which have been demultiplexed after being multiplexed, the timing to output the null packets with time information is adjusted with reference to the time information given to the null packets with time information. The present technology can be applied to, for example, a receiving device that can receive a plurality of streams.