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Method for the encoding of a compressed video sequence derived from the same video sequence compressed at a different bit rate without loss of data

IP.com Disclosure Number: IPCOM000008165D
Publication Date: 2002-May-22
Document File: 8 page(s) / 162K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the encoding of a compressed video sequence given the same video sequence compressed at a different bit rate without loss of data (lossless). Benefits include improved functionality and improved performance.

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Method for the encoding of a compressed video sequence derived from the same video sequence compressed at a different bit rate without loss of data

Disclosed is a method for the encoding of a compressed video sequence given the same video sequence compressed at a different bit rate without loss of data (lossless). Benefits include improved functionality and improved performance.

Background

              Scalable codecs and transcoding are two known methods to provide content at different bit rates or quality.

              Scalable codecsgenerate bit streams representing individual layers such that enhancement layers can be combined with the base layer to produce video of higher (spatial, temporal, or SNR) qualities. Typically, low‑resolution data is used for the compression of higher-resolution data. As a result, the higher resolution stream is coupled with the data of the lower-resolution stream (the reverse is also possible). The result is a lower coding efficiency when compared to single-layer encoding. A single layer stream cannot be extracted from the base and enhancement layers without re‑encoding the video (requantization with reduced coding efficiency).

              Transcodingtakes a single layer video stream and generates from it another single layer stream but at a lower bit rate to meet storage or bandwidth constraints. This implies that quantized data is requantized and compared to the direct encoding of the original data at a lower rate. A loss of 1 dB typically occurs. Transcoders can be as simple as the cascade of a decoder and encoder. Alternatively, the decoding and encoding process can be integrated by reusing information, like motion vectors. The processing may be performed in the frequency domain.

General description

              The disclosed method enables multiple single-layer bit streams of a video sequence to be efficiently stored or transmitted using lossless compression of a reference stream. One of the single layer streams is designated as the reference stream. The other single layer streams are losslessly encoded with respect to that reference stream to form a differentially encoded stream. With this approach, given the reference stream and a differentially encoded stream, the corresponding single layer stream that was obtained by encoding the uncompressed video data can be reconstructed without loss of data.

              The disclosed method applies to applications that require a video sequence at different rates. This situation occurs in streaming servers for clients with various bandwidth capabilities. A content provider may also want to provide its content at different rates as a function of the service a client has paid for or what the content will be used for, such as high quality for editing, lower quality for preview. The content owner could be a home user who wants high-quality streams for her digital video clips for archiving and lower-quality streams for posting on the web or for viewing on his PDA. Content with different bit rates can also be used in peer‑to‑peer ...