1 / 8

HDTV Video and AC-3 Payload Formats

HDTV Video and AC-3 Payload Formats. Ladan Gharai (ladan@isi.edu) Allison Mankin (mankin@isi.edu) USC/ISI. Motivation. HDTV formats are starting to be used in studio, distributions, broadcasts, and in high bandwidth nets US commercial broadcasts of 1920x1080 as of 5/99

varick
Download Presentation

HDTV Video and AC-3 Payload Formats

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HDTV Video and AC-3 Payload Formats Ladan Gharai (ladan@isi.edu) Allison Mankin (mankin@isi.edu) USC/ISI

  2. Motivation • HDTV formats are starting to be used in studio, distributions, broadcasts, and in high bandwidth nets • US commercial broadcasts of 1920x1080 as of 5/99 • Use of uncompressed - tradeoffs of decoding versus bandwidth; some very high resolution applications • Bandwidths from 176 Mbps (SDTV 640x480 24P) to 1.49 Gbps (1920x1080 60I/30P) • Target bandwidths of digital broadcast - 19.4 Mbps digital cable - 39.1Mbps

  3. HDTV over RTP • US HDTV standardized by ATSC (Advanced Television Standards Committee) • www.atsc.org • Europe’s HDTV standard is DVB • www.dvb.org • Major differences • Terrestrial receiver technology (COFDM vs 8VSB) • DVB uses MPEG audio, ATSC uses AC-3 Dolby • Others are using one of these, if using digital formats

  4. RTP Payload for HDTV Video Streams draft-avt-hdtv-video-00.txt drafted, not yet submitted • Compressed HDTV video mostly covered by RFC 2250 - MPEG-2 transport and MP@HL. DVB audio? • Payload type issue for compressed • Some expectation that some HDTV decoders will break if handed an arbitrary MPEG-2 stream • Uncompressed HDTV • Cover color sub-sampling of both 4:2:0 and 4:2:2 • Related to BT.656 (ITU-R) (RFC 2431), but BT.656 lacks 4.2.0 and only covers 525/625 lines (HDTV up to 1080 lines)

  5. RTP Payload for AC-3 Audio Streams draft-avt-ac3-audio-00.txt drafted, not yet submitted. • Place an integral number of sync frames per RTP packet • Fragmentation needs to be handled - frame sizes at 48Khz range from 128-2560 bytes • Sync frames must be reassembled prior to decoding, as decoder takes all or nothing • No dependency on other frames • AAC-like audio repair seems applicable

  6. P: progressive scan I : interlaced scan

  7. left right center left surround right surround low frequency effects 384kbps AC-3 encoder Dolby Digital AC-3 • A digital compression algorithm from Dolby labs • Input: 1 to 6 PCM audio channels • Output: a serial bit stream with data rates of 32kbps to 640kbps • Low bandwidth is achieved by encoding multiple channels as a single entity • example: • 6ch * 48kHz *18bits = 5.184Mbps

  8. 256 samples SI BSI SI BSI AB0 AB1 AB2 AB3 AB4 AB5 Aux crc sync frame AC-3 Audio streams • An AC-3 audio stream is a sequence of same size “sync frames” • Each sync frame is an independent data unit, I.e. it does not need require any other data to be decoded • an AC-3 decoder must be presented with the entire sync frame AB: Audio Block SI: synchronization information header BSI: bit stream information header CRC: cyclic error check

More Related