[分享] XCD相关

sgabello

从国外论坛转来的 我没翻译
如果有人感兴趣的话 我翻成中文好了

在这里强力推荐一把

1) What is XCD?
XCD means that you store normal data files in the same way as VCDs, meaning that one of the 3 layers of error correction of normal data CDs is removed and the free space is available for data
The correct name of the recording format is Mode 2 Form 2.

2) How much data can i store on a XCD?
XCDs can hold (2324/2048) times more data than normal data CDs, i.e. a 700 MB disc can hold 795 MB. If you combine it with Gigarec e.g. on 1.2x setting, you get 960 MB, and so on.

3) How can i create XCDs?
You have to use the Mode2 CD Maker Tool (Doom9 Guide)
some cd burning progs, like cdrdao, can burn any data as mode 2 form 2, but i am not sure if the results would be playable without problems

4) How can i play XCDs?
You need a CDXA directshow filter:
there are actually two available: from avih and gabest

5) Which files does XCD work with?
With all files for which XCD-capable/Directshow players exist, such as AVI, MKV, OGM, MP4 or RM/RMVB.
Be aware of that AVIs on XCDs can be unplayable when the header or the index gets b0rked, MKVs and OGMs also when the header gets b0rked (so handle your XCDs with care)

6) Is there any error correction available on XCDs?
XCDs have as much error correction as audio cds, meaning that scratches that do not destroy more than 2mm of consecutive data can be corrected. Note that this length is smaller if you use Gigarec.

7) How can i check the status of a XCD before data gets b0rked?
Do a Cx-Scan, for example using the PlexTools with a Plextor Premium drive. If you see E22 errors reported, the disc is short before getting b0rked. If you don't have a Plextor Premium drive, use Nero CD Speed -> Quality check. Unfortunately, this check reports different errors for different drives, but many drives will report errors there before any data gets b0rked.

8) Are CRC elements in containers useless on XCDs?
Mostly yes, each sector of 2324 bytes of user data gets an 32 bit CRC value on XCDs (although it is not mandatory, the space it consumes cannot be used for any other purpose, so any Mode2Form2-Authoring-Software should write this CRC value), so you will know anyway if any data gets b0rked due to too bad scratches or due to having vampire discs exposed to sunlight. Another CRC value won't tell you anything new.

8) Compatibility of XCDs?
Except for a few b0rked drives, like the LG 16x DVD-ROM, most PC drives can read XCDs.

9) Is it possible to make X-DVDs?
DVDs cannot be trifled with in the same amount or way as CDs. Something like X-DVD is not possible with the current specifications.

10) Windows sees larger files on the disc than the source was?
Although there are only 2324 bytes of data in a sector, there are 28 more bytes of overhead (sector header, crc). If you access files on XCDs on M$ Windows, it will read the entire set of 2352 bytes, just as if they all belonged to the file! The application has to throw out those 28 bytes! (This is what XCD-Filters do). It is also up to the app to check the CRC in those 28 bytes for correctness.

11) How can i copy data from XCD to my harddisk?
Never ever copy XCD files directly to hard disc! If you do that, those 28 bytes of overhead will stay in the file, and the file is still an XCD-File. If you then make a new XCD from that file, you get more overhead, the file grows again, and the XCD-Filter must be run twice to read the file! The same is happening of course with VCD and SVCD.
To copy your XCD to hd use the dat2file programm bundled with Mode2 CD Maker, Extractor or AVI-Mux GUI

12) I want to read more about XCD! Were can i find more infos?
try the official Sourceforge Project page and ReferenceDivX's Docs about MCF-CD and of course doom9

13) Can I safely use XCD then?
After reading and understanding this FAQ, you know enough about XCD to decide if you consider the risk of loss of data too high or not!