A standard for digital television (DTV) that supports display formats that are larger and higher in resolution than either legacy analog TV or digital standard definition television (SDTV). Specifically, HDTV specifies two formats, as detailed in Table H-2.

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 8level 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.