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Speaker AdvisorClassStudent IDMA2G0107Author Chin-Feng Lai Han-Chieh ChaoPublished2013

Cloud-Assisted Real-Time transrating for http live streaming1OutlineIntroductionResearch MethodsResultsConclusionIntroductionThe public have gradually changed from viewing offline medias to viewing medias using network streaming on personal computers or hand-held devicesThe existing multimedia streaming technologies can be approximately divided into:Push streaming modeRequest streaming mode3Research MethodsCloud-ssisted Real-Time adaptive transcoding system

4Research MethodsNormal Mode:

Active Mode:

Conservative Mode:

N pB itcpdumpB nextB endT remained

5Research MethodsTransrating state machine

BCA

Tb Normal Mode Normal ModeNormalType A Error Type C Error Normal Temp A Normal Temp CType A Error Type C Error Active Conservative Active Type C Error Temp Active Conservative Conservative Type A Error Normal

6Research MethodsFinally, in the operational flow of the server transcoding, when the client sends a request to the server to download media segments, the segment start is entered.

In the download period of the client, the server continuously records the size of each packet and transmission time.

When the download is completed, the server immediately calculates the average download bit rate of current media segment, and compares it with the average download bit rate of the previous media segment to obtain an error; at this moment, the mode transition state machine determines the mode, and dynamically generates the estimated bit rate value of the next media segment according to the transcoding strategy corresponding to each state.

;7ResultsBitrate to segment for scenario

S1S1

8ResultsBandwidth usage comparison for scenario

9ResultsAnalysis of PSNR for scenario

PSNR10ResultsPSNR comparison for scenario

PSNR11ConclusionThis article designs a cloud-assisted real-time transrating mechanism based on HLS protocolImplements the bandwidth recoder, segment transrater, and segment rediretor on the server, instantly analyzes the on-line quality between client and server without changing the HLS server architectureProvides the optimum media quality, in order that the client leads the HTTP requirement in the transrated media segment using HTTP redirection technology.HLS

transraterrediretorHLS

HTTPtransratedHTTP

12ConclusionMultimedia segments can be dispersed in different servers in the future, or can construct cloud access systems among HLS servers, even among network domains, in order to reduce the probable load on a single server or a single network domain, thus, increasing the overall bandwidth utilization rate and improving media quality for global users.HLS13