Software Design Of H.264 To HEVC Video Transcoder Based On C66AK Multi-core Processor

With the rapid development of science and technology,multimedia information has been integrated into our lives,and video data is an important part of it.As people’s demands on video resolution and quality are increasing,the storage and transmission of video data are facing great challenges.HEVC is the latest standard that reduces the bitrate by nearly 50 % at the same visual quality compared with H.264,it can save a lot of video stream storage space and network bandwidth.The majority of existing digital video resources exist in H.264 compression format.Due to many factors such as products’ price and update cycle,HEVC encoding device can not immediately replace the H.264 encoding device.Therefore,transcoding from H.264 to HEVC has important practical significance in the network transmission and storage.This dissertation has designed and implemented the software of H.264 to HEVC video transcoder based on C66 AK multi-core processor.The main contents are as follows:(1)The key technology of H.264 and HEVC and the research status of video transcoding technology are been presented.C66 AK multi-core processor is adopt as the hardware platform.Then,the overall transcoding software framework is designed and the software development environment is built.In the Linux platform,a cross-compiler environment and the CCS integrated development environment are built,the U-Boot is programmed to Nandflash through the CCS.After the U-Boot was started,the kernel and file system are wrote to Nandflash with TFTP protocol.In the Windows platform,the CCS integrated development environment is built.(2)H.264 decoding software is designed based on FFmpeg software framework.In the software design process,the debug of the decoding software is completed in the Visual Studio environment,and then it is transplanted into the ARM core of the C66 AK with code optimization performed,in order to improve the decoding performance.(3)HEVC encoding software is designed based on x265 software framework.In the software design process,the debug of the encoding software is completed in the Visual Studio environment,then it is transplanted into the single DSP core of the C66 AK.When the encoding software can correctly encode an image on the single DSP core,the image is further divided into four bands,then,each DSP core encodes a slice to achieve HEVC multi-core parallel encoding.(4)The message and data are transmitted between the ARM core and DSP core by the inter-core communication mechanism.When the ARM core decodes an H.264 bitstream and saves the decoded frame in the DDR input buffer,the message is sent to the DSP core through the MessageQ message mechanism,then,DSP core encodes the decoded frame.After the DSP core encoded the decoded frame to HEVC bitstream and saved the bitstream to the DDR output buffer,the message is sent to the ARM core,then,the ARM core sends the HEVC bitstream to the PC client.(5)The video transcoding application modules are designed on the ARM core,including the design of the interactive protocol between the application module and the transcoding client,the ARM core receiving H.264 bitstream sent by transcoding client through UDP protocol and the ARM core sending the transcoded HEVC bitstream to the transcoding client through the UDP protocol.