Research Of DMB Video Encoding Optimization Technology

Digital Multimedia Broadcasting(DMB) has gradually been applied in the field of info diffusion in recent years. It has the characteristics of anti-noise, mobile reception ability, program content diversity and high frequency spectrum utilization. DMB system uses H.264 as video compression standard. The distributive bitrate of video business is low due to the limitation of DMB bandwidth. H.264 is based on block video coding system and has blocking effect in the low bit rate. It can affect the video quality. Besides, info diffusion requires that the broadcast content is authoritative and identifiable. These are challenges for video transmission in the DMB info diffusion system. In view of the above problems, based on the laboratory original DMB video encoder, this thesis can reduce the blocking effect and improve the video quality by further optimizing the video coding algorithm. At the same time, the video watermarking function is realized through the open source FFmpeg. It can indicate the source and the authority of the information.Firstly, this thesis introduces DMB video encoder related technology of H.264 video coding standard and FFmpeg audio and video codec library. Studied the generation mechanism of H.264 blocking effect. Adopted the optimization method of DCT coefficient quantization to reduce the blocking effect and improve the video quality. Then, this thesis studied the video and audio filters from libavfilter of FFmpeg library. Completed the function of video watermarking by software programming. Indicated the source of the information to reflect the authority. This thesis also improved the original encoder in the laboratory, including updating the FFmpeg library version to support more video formats, encoding arbitrary frame rate video files and optimizing software interface.In order to fully verify the results of the research, DMB video quality was evaluated from two sides of subjectivity and objectivity. The results indicate that the average score of the improved DMB video quality is one or two points higher than the original video in the subjective evaluation, and Structural Similarity(SSIM) values increased by approximately 0.002 in the objective evaluation. A lot of tests to further reveal that the encoder operated stably, watermark overlay function is normal, the encoder is optimized, and the quality of DMB video business has been improved integrally.