Video transcoding is the process of converting compressed video signals to adapt video characteristics such as video bit rate, video resolution, or video codec, so as to meet the specifications of communication channels and endpoint devices. A straightforward transcoding solution is to fully decode and encode the video. However this method is computationally expensive and thus unsuitable in applications with tight resource constraints such as in software-based real-time environment. Therefore, efficient transcoding meth- ods are required to reduce the transcoding complexity while preserving video quality. Prior transcoding methods are suitable for video coding standards such as H.264/AVC and MPEG-2. H.265/HEVC has introduced new coding concepts, e.g., the quad-tree-based block structure, that are fundamentally different from those in prior standards. These concepts require existing transcoding methods to be adapted and novel solutions to be developed. This work primarily addressed the issue of efficient HEVC transcoding for bit rate adaptation (reduction). The goal is to understand the transcoding behaviour for some straightforward transcoding strategies, and to subsequently optimize the complexity/quality trade-off by providing heuristics to reduce the number of coding options to evaluate. A transcoder prototype is developed based on the HEVC reference software HM-8.2. The proposed transcoder reduces the transcoding time compared to full decoding and encoding by at least 80% while inducing a coding performance drop within a margin for 5%. The thesis has been carried out in collaboration with Ericsson Research in Stockholm / Video content is produced daily through variety of electronic devices, however, storing and transmitting video signals in raw format is impractical due to its excessive resource requirement. Today popular video coding standards such as MPEG-4 and H.264 are used to compress the video signals before storing and transmitting. Accordingly, efficient video coding plays an important role in video communications. While video applications become wide-spread, there is a need for high compression and low complexity video coding algorithms that preserve image quality. Standard organizations ISO, ITO, VCEG of ITU-T, and collaboration of many companies have developed video coding standards in the past to meet video coding requirements of the day. The Advanced Video Coding (AVC/H.264) standard is the most widely used video coding method. AVC is commonly known to be one of the major standards used in Blue Ray devices for video compression. It is also widely used by video streaming services, TV broadcasting, and video conferencing applications. Currently the most important development in this area is the introduction of H.265/HEVC standard which has been finalized in January 2013. The aim of standardization is to produce video compression specification that is capable of compression twice as effective as H.264/AVC standard in terms of coding complexity and quality. There is a wide range of platforms that receive digital video. TVs, personal computers, mobile phones, and tablets each have different computational, display, and connectivity capabilities, thus video has to be converted to meet the specifications of target platform. This conversion is achieved through video transcoding. For transcoding, straightforward solution is to decode the compressed video signal and re-encode it to the target compression format, but this process is computationally complex. Particularly in real-time applications, there is a need to exploit the information that is already available through the compressed video bit-stream to speed-up the conversion. The objective of this thesis is to investigate efficient transcoding methods for HEVC. Using decode/re-encode as the performance reference, methods for advanced transcoding will be investigated. / 0760609667 Bäckgårdsvägen 49, 14341 Stockholm
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:bth-2670 |
| Date | January 2013 |
| Creators | Tamanna, Sina |
| Publisher | Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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