Um Contador Controlado por Semáforos Para a Correção de PCR

Abstract

Resumo-O fluxo de transporte MPEG-2é muito utilizado na transmissão deáudio, vídeo e dados multiplexados, fornecendo bases de tempo para os programas enviados. Esta informação, conhecida como PCR e também responsável pela sincronização do receptor, pode sofrer erros durante a sua transmissão, devidò a cadeia de processamento entre transmissor e receptor. Este artigo introduz um novo método de correção de PCR, baseado em um contador controlado por semáforos, queé capaz de fornecer uma referência de tempo estável para o decodificador. A arquitetura do módulo de correção, que possui características como complexidade computacional e requisitos de hardware reduzidos,é apresentada e comparada a métodos tradicionais. Resultados de simulação mostram que o método propostoé eficaz e mantém um baixo nível de jitter na saída do sistema. Palavras-Chave-Correção de PCR, MPEG-2, fluxo de transporte, semáforo Abstract-The MPEG-2 transport stream is used in many systems for transporting multiplexed audio and video in a transparent way, providing time bases for the transmitted programs. Such information, which is called PCR and is also responsible for synchronizing the receiver, may suffer from inaccuracies, due to the processing chain between transmitter and receiver. This paper introduces a new PCR correction method named as the semaphore-controlled counter, which provides a stable time reference for the decoder. The correction module architecture is presented and compared to traditional methods, exibiting features like low computational complexity and hardware requirements. Simulation results show that the proposed method is effective and provides small jitter levels at the system output.

A Framework for Adaptive PCR Jitter Correction in MPEG-2 TS Processors

“…In this way, the joint rate adaptation and PCR correction algorithm tries to predict the most favorable moment for sending PCR packets. Even if a MPTS is processed, only one set of accumulators is employed, which is possible due to the use of a semaphore structure [11] for shared access.…”

“…One possible solution is to use the compensation approach, as presented in section II-B; However, even with only one program or PCR values of different time bases far apart from each other, many arithmetic operations are performed, which increases the computation complexity of the whole infrastructure. In the present work, it was decided to use the semaphore controlled infrastructure, introduced by Savino and Filho [11]. Its main advantage is that the majority of correction procedures are performed by direct loading the current PCR into the correction module, without the use of intermediate stamps.…”