Tuesday, March 30, 2010

High-definition television

High-definition television (or HDTV, or just HD) refers to video having resolution substantially higher than traditional television systems (standard-definition TV, or SDTV, or SD). HD has one or two million pixels per frame, roughly five times that of SD

HDTV broadcast systems are identified with three major parameters:

  • Frame size in pixels is defined as number of horizontal pixels × number of vertical pixels, for example 1280 × 720 or 1920 × 1080. Often the number of horizontal pixels is implied from context and is omitted.
  • Scanning system is identified with the letter P for progressive scanning or I for interlaced scanning.
  • Frame rate is identified as number of video frames per second. For interlaced systems an alternative form of specifying number of fields per second is often used.

While referring to HDTC Specifications, we usually 1080p, what does it mean here....


1080 horizontal lines with Progressive scanning...(Another type of well known scanning Interleaving..)




High-definition display resolutions

Video format supportedNative resolution (W×H)PixelsAspect ratio (W:H)Description
ActualAdvertised (Mpixel)Image[clarification needed]Pixel[clarification needed]
720p
1280x720
1024×768
XGA
786,4320.816:9[clarification needed]4:3[clarification needed]Typically a PC resolution (XGA); also a native resolution on many entry-level plasma displays with non-square pixels.
1280×720
921,6000.916:91:1Standard HDTV resolution and a typical PC resolution (WXGA), frequently used by video projectors; also used for 750-line video, as defined in SMPTE 296M, ATSC A/53, ITU-R BT.1543.
1366×768
WXGA
1,049,0881.0683:384
(approx. 16:9)
1:1
approx.
A typical PC resolution (WXGA); also used by many HD ready TV displays based on LCD technology.
1080p/1080i
1920×1080
1920×1200
2,073,6002.116:101:1Standard HDTV resolution, used byFull HD and HD ready 1080p TV displays such as high-end LCD, Plasma and rear projection TVs, and a typical PC resolution (lower than WUXGA); also used for 1125-line video, as defined in SMPTE 274M, ATSC A/53, ITU-R BT.709;


Monday, March 29, 2010

What is TAR File?

Tar (derived from tape archive and commonly referred to as "tarball") is both a file format(in the form of a type of and the name of a program used to handle such files.

Conventionally, uncompressed tar archive files have names ending in ".tar".

Unlike ZIP archives, tar files (somefile.tar) are commonly compressed as a whole rather than piecemeal. Applying a utility such as gzip, bzip2, lzip, lzma or compress to a tar file produces a compressed tar file, typically named with an extension indicating the type of compression ( e.g.: somefile.tar.gz).


A tar file is the concatenation of one or more files. Each file is preceded by a 512-byte record. The file data is written unaltered except that its length is rounded up to a multiple of 512 bytes and the extra space is zero filled. The end of an archive is marked by at least two consecutive zero-filled records. (The origin of tar's record size appears to be the 512-byte disk sectors used in the Version 7 Unix file system.)