Research On Video Transcoding Technology Based Bit-rate Transcoding And Resolution Transcoding

With the development of video conding technology and the widespread adopt of multimedia communication,video and people's lives are getting closer and closer.Different video application has different requirement about the video format,network bandwidth and the performance of the video decoder,in addition,for different domain the video coding standard is different too.In order to make a video server provide high quality services to different terminals under heterogeneous networks,we have to use video transcoder technology in the interface.The purpose of video transcoder is to decrease the computational complexity in the condition of keeping the image quality and the bit-rate.But we can't gain all the benefits simultaneity, so we have to make a choice.Furthermore, in order to make the bit-rate meet the stability of the internet, we have to make good use of bit-rate control technic to control the process no matter what we are coding or transcoding the video.The main works of the thesis are as follows:(1) we focused on the bit-rate transcoding and the resolution transcoding base on the DCT domain.First we introduced the coding architecture of the newest video compression and coding standard named H.264.Then, we described the transcoding theory and the main transcoding structure base on the H.264 standard,in the mean time we discussed the problem we will confront on the bit-rate transcoding and resolution transcoding in the DCT domain.(2)In fact, the main computational cost of intra-frame coding is concentrated on the choice of mode decision and predict direction.Here, we proposed a fast intra mode decision algorithms based on the statistic characteristic.After some tests on several video sequence in the different quantization step and contrasted on bit-rate,video quality and computational complexity,we proved that the new arithmetic is efficiency.(3)In order to make the transcded video be stable,we proposed a method of predict distortion based on the DCT domain for the newly proposed bit-rate control model which is based on the Cauchy distribution,and consider the new quantization step can be used to accelerate the macroblock mode decision process,then we improved the mode decision arithmetic we just have proposed. Also we did some tests on several video sequence and contrast on bit-rate,video quality and computational complexity,we proved that the improved arithmetic can gain better performance.(4)we payed attention to the heterogeneous transcoder composed by three transcoding prosses,spatial resolution downscale,frame-rate downscale and bit-rate reduction.We first discussed the main problems we'll meet,then associate with the bit-rate control we assumed a combinated transcoder model based on DCT domain.