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Method for controlling artifacts from encode/decode clock skews by modifying the PTS

IP.com Disclosure Number: IPCOM000126987D
Publication Date: 2005-Aug-16
Document File: 2 page(s) / 85K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for controlling artifacts from encode/decode clock skews by modifying the presentation time stamp (PTS). Benefits include improved functionality, improved performance, and improved design flexibility.

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Method for controlling artifacts from encode/decode clock skews by modifying the PTS

Disclosed is a method for controlling artifacts from encode/decode clock skews by modifying the presentation time stamp (PTS). Benefits include improved functionality, improved performance, and improved design flexibility.

Background

              When receiving live streaming analog or digital content for display by a processor on a system that is faster than the transmitter, the input buffers become starved for data.


              In the case of streaming digital video, the transmitter typically has an encoder and a transport stream generator that is driven by a clock. The PTS informs the receiver when to present the frame. The program clock reference (PCR) enables the receiver to resynchronize the clock with the transmitter. This practice requires an isochronous transport, which is not supported by several common industry standards. Clock skew occurs on nonisochronous networks because synchronous points in the transmission are not synchronously delivered.

              One commonly accepted practice for nonisochronous physical/transport layers is to use the receiver buffer level to adjust the playback clock. Some heuristic is added to keep the buffers on the receiver from overflowing or underflowing.
              If the encode and decode clocks are out of phase, data can be dropped at the decoder because buffers either underrun or overrun. In many cases, the receiver playback clock is not adjustable and a hardware adjustment of the decode clock will not work.

General description

              The disclosed method controls artifacts from encode/decode clock skews by modifying the PTS.

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to controlling artifacts from encode/decode clock skews by modifying the PTS

•             Improved performance due to keeping t...