Slide 1Thesis outline:What is multiplexing?Applications of multiplexingSlide 5The need for video and audio compressionWhy AVS China video ?Overview of AVS China standard [5]AVS-video profiles & their applications [4]Coding tools of AVS part 2 video codecAVS China part 2 video encoder [2]AVS video decoder [12]AVS video encoded bit stream formatSlide 14Picture coding type used in AVS-video bit streamNAL unitSlide 17NAL unit header descriptionNAL unit type according to the start code values [14].Why AAC audio?AAC audioAAC audio stream formatADTS header format [18]Factors to be considered for multiplexing and transmissionSlide 25Packetized elementary streams (PES)Packetized elementary streams (PES) [22]PES header descriptionFrame number as time stampMethod adopted in MPEG 2 systems standard for time stampsSlide 31Transport stream packetizationTransport stream [22]TS packet header [22, 25]TS packet header descriptionAdopted multiplexing methodCalculating playback time of each TS packetMultiplexed transport stream [22]De-multiplexing processBuffer fullness at the de-multiplexer using the adopted methodSynchronization and playbackSynchronization and playbackResultsSynchronization resultsConclusionsTest conditionsFuture WorkReferencesReferencesReferencesReferencesReferencesSwaminathan SridharMultimedia Processing LabUniversity of Texas at ArlingtonMULTIPLEXING OF AVS CHINA PART 2 VIDEO WITH AAC BIT STREAMS AND DE-MULTIPLEXING WITH LIP SYNC DURING PLAYBACKThesis outline:What is multiplexing?Applications of multiplexing.The need for choosing AVS video and AAC audio codecs.Video & audio elementary stream formats.Multiplexing process.De-multiplexing process.Lip synchronization during playback.Results and conclusions.Future work.References.What is multiplexing?A multimedia program is a combination of multiple elementary streams such as video and audio.Multiplexing is the process of converting multiple elementary streams such as video an audio streams into a single transport stream for transmission.It conserves the usage of transmission channels.Applications of multiplexingMultiplexing is used in areas of applications such asATSCDVB-T DVB-SDVB-HIPTVThe digital transmission/reception process adopted in the ATSC standard [22]The need for video and audio compressionWith the advent of high definition television transmission schemes high quality video and audio data are transmitted which occupy a lot of bandwidth over a transmission channel.To address this issue the video and audio data are compressed using efficient compression schemes such as AVS China video codec and AAC audio codec.Why AVS China video ?AVS (audio video coding standard) China is the latest digital video coding standard developed by the AVS work group of China.AVS video codec employs the latest video coding tools which primarily targets standard definition (SD) and high definition (HD) video compression.Compared to the previous video coding standards such as MPEG-2 and MPEG-4, AVS achieves the same quality of video with significantly lower bit rates or vice versa.Overview of AVS China standard [5]AVS-video profiles & their applications [4]Coding tools of AVS part 2 video codecIntra prediction : 8x8 block based intra prediction.5 modes for the luminance component namely the DC, horizontal, vertical, down left and down right and 4 modes for the chrominance component namely the DC, horizontal, vertical and plane mode are specified.Motion compensation : 16x16, 16x8, 8x16 and 8x8 block sizes.Motion vector resolution: ¼ pixel accuracy with 4-tap interpolation filter.Transform: 8x8 integer cosine transform.Quantization and scaling with scaling only in the encoder.Entropy coding: context based 2D-VLCDe-blocking filter: performed around the 8x8 boundariesAVS China part 2 video encoder [2]AVS video decoder [12]AVS video encoded bit stream formatStart code: It consists of start code prefix and start code value. Start code prefix: A string of 23 zero bits followed by a single bit with a value of ‘1’ i.e. ‘0x000001’ which are all byte aligned. This is followed by start code value.Start code value: It is an 8 bit integer that identifies the start code type.Start code types & start code values used in the AVS-video bit stream [8]Picture coding type used in AVS-video bit streamPb_picture_start_code : The bit string format is ‘0x000001B6’ which indicates the start code of P or B picture.Picture_coding_type: It is a 2-bit unsigned integer which specifies the coding type of a picture as shown in Table 1. Table 1 Coding type of a picture [8]Picture_coding_type Coding type00 Forbidden01 Forward inter prediction (P)10 Bidirectional inter prediction (B)11 ReservedNAL unit NAL unit stands for network abstraction layer unit which is a type of packetization that prefixes certain headers to the encoded video bit stream.It was designed to provide a network friendly environment for transmission of video data .It mainly addresses video related applications such as video telephony, video storage, broadcast and streaming applications, IPTV etc.The syntax for NAL unit is defined in H.264 standard but AVS part 2 standard does not define any syntax for the NAL unit.NAL unit mapping with the encoded AVS video stream•The basic syntax for the NAL unit is shown in figure 1. Figure 1 NAL unit syntax [13].•NAL unit consists of a 8 bit header followed by the payload.•The procedure for mapping AVS video stream with NAL unit is to mapthe data between every start code prefixes i.e. ‘0x000001’ in the AVSvideo stream into a NAL unit (which includes the start code value but not the code prefixes) and then add a 1-byte header before the startcode value.NAL unit header descriptionIt is a 8 bit header consisting of the following parameters.Forbidden_zero_bit : which is a 1 bit value and it is always ‘0’.Nal_ref_idc : which is a 2-bit unsigned integer value. It indicates the priority of the type of data carried in the NAL unit based upon the start code type. This value should not be zero for I frames.Nal_unit_type : which is a 5-bit unsigned integer value and therefore 32 types of NAL units are allowed. This value indicates the type of data carried in the NAL payload.NAL unit type according to the start code values [14].Why AAC audio?AAC codec showed superior
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