"Data Capacity of CDs [Tutorial] Abstract You can fit on a S/VCD without overburning: - approx. 735 MB of MPEG data onto a 74min/650MB disc - approx. 795 MB of MPEG data onto an 80min/700MB disc You can fit on a CD-ROM without overburning: - approx. 650 MB of data onto a 74min/650MB disc - approx. 703 MB of data onto an 80min/700MB disc ---------------------------------------------------------------Introduction Let us ignore for now the terms of megabyte for CD capacity and try to understand how the data is
As well all know, the data is stored digitally as binary data. This means, however the actual info An a CD-R disc, the data is physically on an organic dye layer which simulates the metal layer on ----------------------------------------------------------------
How is the information structured Now, on the CD, the information isn’t just organised from beginning to end willy-nilly. Otherwise, Rather, the information is organised in sectors. Consider a sector as like a page in a book. Just Now, remember that the CD was original made to hold audio data. It was decided, that the CD would Now, with this in mind, we can work out the total data capacity of user data for 1 sector. ---------------------------------------------------------------The total data capacity of user data of 1 sector on a CD CD audio uses uncompressed PCM stereo audio, 16-bit resolution sampled at 44.1 kHz. Thus 1 second of audio contains: 16 bits/channel * 2 channels * 44100 samples/second * 1 second = 1411200 bits = 176400 bytes Since there are 75 sectors per second 1 sector = 176400 bytes / 75 = 2352 bytes One sector on a CD contains 2352 bytes max. ----------------------------------------------------------------
The concept of different MODES and FORMS of burning Now, audio CD was well and good, but the medium would become much more useful if you could store o Now, the audio-CD uses the ENTIRE sector for audio data.
However, for CD-ROMs this caused a problem. Simply, CDs and the CD reading mechanisms were not 100
Thus, for CD-ROMs, part of each sector is devoted to error correction codes and error detection co This burning mode is either MODE1 or MODE2 Form1.
----------------------------------------------------------------
MODE2 Form2 sectors of VCDs and SVCDs Now, for VCDs and SVCDs, the video tracks do not necessarily require the robust error correction a
S/VCDs video tracks are burnt in what is called MODE2 Form2 sectors. In this mode, only 2324 bytes This is MUCH MORE than for CD-ROMs, but still less per sector than audio CD. ----------------------------------------------------------------
The disc capacities of CD-ROMs, audio-CDs and VCDs Now, obviously what ultimately determines the capacity of a disc is the total number of sectors it The secondary determinant is the burning mode of the disc.
For audio CDs, it is as if you could fill each page from top to bottom with audio data as the enti
For CD-ROMs, it is as if you need to first rule a margin and then leave the bottom part of each pa
For S/VCDs, we still need to rule a margin on the page, but we don’t have to worry about the footn Now remember, 1 second on a CD = 75 sectors. Thus: - 74 min CD = 333,000 sectors - 80 min CD = 360,000 sectors
Data capacity in Mb for an audio-CD 74 min = 333,000 sectors * 2352 bytes / sector = 783216000 bytes = 746.9 Mb 80 min = 360,000 sectors * 2352 bytes / sector = 846720000 bytes = 807.5 Mb
Data capacity in Mb for a CD-ROM 74 min = 333,000 sectors * 2048 bytes / sector = 681984000 bytes = 650.4 Mb 80 min = 360,000 sectors * 2048 bytes / sector = 737280000 bytes = 703.1 Mb
Data capacity in Mb for a S/VCD 74 min = 333,000 sectors * 2324 bytes / sector = 773892000 bytes = 738.0 Mb
80 min = 360,000 sectors * 2324 bytes / sector = 836640000 bytes = 797.9 Mb ---------------------------------------------------------------Conclusions As you can see, the often quoted capacities of 650MB and 700MB refer to CD-ROM capacities.
Due to the fact that S/VCDs use a different burning mode where MORE of each sector is available as
Now, since S/VCDs are not composed of PURELY video tracks and have some unavoidable overheads, the All these capacities are available BEFORE overburning. Overburning is where you burn MORE sectors ---------------------------------------------------------------This is a demo version of txt2pdf PRO v.9.2 Developed by SANFACE Software http://www.sanface.com/ Available at http://www.sanface.com/txt2pdfPRO.html
..."
|
You need to upgrade your Flash Player , or try to enable javascript in order see this document properly.
|
|
Comments
