What is padding

One article on burning a bootable cd mentioned padding - as be sure to apply padding. I haven’t had any luck finding a definition/explanation googling or searching MyCE. Inferring from one article it seemed to be a filler added to the end of the cd and from another it seemed to refer to moving the start position of audio tracks [somehow] for compatibility to old cd players.

chk this out, it might help

Recording schemes
See also: Optical disc recording technologies
CD recording on personal computers was originally a batch-oriented task in that it required specialised authoring software to create an “image” of the data to record, and to record it to disc in the one session. This was acceptable for archival purposes, but limited the general convenience of CD-R and CD-RW discs as a removable storage medium.

Packet writing is a scheme in which the recorder writes incrementally to disc in short bursts, or packets. Sequential packet writing fills the disc with packets from bottom up. To make it readable in CD-ROM and DVD-ROM drives, the disc can be closed at any time by writing a final table-of-contents to the start of the disc; thereafter, the disc cannot be packet-written any further. Packet writing, together with support from the operating system and a file system like UDF, can be used to mimic random write-access as in media like flash memory and magnetic disks.

Fixed-length packet writing (on CD-RW and DVD-RW media) divides up the disc into padded, fixed-size packets. The padding reduces the capacity of the disc, but allows the recorder to start and stop recording on an individual packet without affecting its neighbours. These resemble the block-writable access offered by magnetic media closely enough that many conventional file systems will work as-is. Such discs, however, are not readable in most CD-ROM and DVD-ROM drives or on most operating systems without additional third-party drivers.

The DVD+RW disc format goes further by embedding more accurate timing hints in the data groove of the disc and allowing individual data blocks to be replaced without affecting backwards compatibility (a feature dubbed “lossless linking”). The format itself was designed to deal with discontinuous recording because it was expected to be widely used in digital video recorders. Many such DVRs use variable-rate video compression schemes which require them to record in short bursts; some allow simultaneous playback and recording by alternating quickly between recording to the tail of the disc whilst reading from elsewhere.

Mount Rainier aims to make packet-written CD-RW and DVD+RW discs as convenient to use as that of removable magnetic media by having the firmware format new discs in the background and manage media defects (by automatically mapping parts of the disc which have been worn out by erase cycles to reserve space elsewhere on the disc). As of February 2007, support for Mount Rainier is natively supported in Windows Vista. All previous versions of Windows require a third-party solution, as does Mac OS X.

or this

Overburning is the process of recording data past the normal size limit.

Many disc manufacturers extend a recordable disc to leave a small margin of extra groove at the outer edge. This lead-out was originally intended to provide tolerance for the read head of an audio CD player should it overseek, by providing a padding of up to 90 seconds of silent digital audio.

sounds to me like its just a cushion

Insertion of some meaningless bytes between the end of the last data structure and the start of the next.

For example, when the computer’s word size is 4 bytes, the data to be read should be at a memory offset which is some multiple of 4. When this is not the case, e.g. the data starts at the 14th byte instead of the 16th byte, then the computer has to read two 4-byte chunks and do some calculation before the requested data has been read, or it may generate an alignment fault. Even though the previous data structure ends at the 14th byte, the next data structure should start at the 16th byte. Two padding bytes are inserted between the two data structures to align the next data structure to the 16th byte.

Link:[/B] http://wapedia.mobi/en/Data_structure_alignment

I guess we really need to know what kind of padding are you referring to?


Thanks to all for replies,

I’ve read the replies and followed the link and I’m still reading - or I will be when I get past the latest dire emergency [dying HD]. I get the basic idea that padding is the addition of meaningless bits to take up space so things like memory and optical discs don’t get read from the wrong place. The rest is over my head, but when I run into the term again I’ll be better prepared to figure out what’s meant in that context.