| 单词 | Table H-2: SDTV Scanning Formats |
| 释义 | Table H-2: SDTV Scanning Formats Vertical Lines Horizontal Pixels Aspect Ratio Refresh Rate (fps)* 1080 1920 16:9 24p, 30p, 60i** 720 1280 16:9 24p, 30p, 60p** *fps = frames per second **i = interlaced, p= progressive In comparison to analog TV, DTV offers improved reception, without the ghosting, snowy images, and generally poor audio quality. Issues of signal quality in DTV transmission manifest in artifacts such as blocking, or tiling, and stuttering. The ATSC standard specifies MPEG-2 compression, and the transport subsystem as ISO/IEC 13818. Packet transport involves a serial data stream of packets of 188 octets, one octet of which is a synchronization byte and 187 octets of which are payload.This packet approach is suitable for ATM switching, as each 188-octet MPEG-2 packet maps into the payload of four ATM cells, with only 4 octets of padding required. SDTV employs Reed-Solomon forward error correction (FEC) and 8-level vestigial sideband (8 VSB) RF modulation to support a bit rate of 19.28 Mbps over a 6 MHz terrestrial broadcast channel. Audio compression is based on the AC-3 specification from Dolby Digital and the ATSC. SDTV standards were developed by the Grand Alliance and reviewed, tested, and documented by the Advanced Television Systems Committee ( ATSC) at the request of the United States Federal Communications Commission (FCC). See also 8-VSB, AC-3, analog, artifact, aspect ratio, ATM, ATSC, broadcast, byte, channel, compression, digital, DTV, FCC, FEC, fps, ghosting, Grand Alliance, interlaced scanning, modulation, MPEG-2, NTSC, octet, packet, padding, PAL, payload, pixel, progressive scanning, Reed-Solomon, refresh rate, resolution, RF, scanning, SDTV, SECAM, and synchronize. 74570c08.qxd 9/11/07 12:22 PM Page 224 |
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