[mythtv-users] OT DVD ripping software

Simon Hobson linux at thehobsons.co.uk
Mon Oct 27 16:31:31 UTC 2014


Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:

>> But DVDs have a normal file system - I always thought that there is no
>> problem concerning the reading quality. The OS and the DVD drive have
>> to handle reading errors. And if the disc isn't readable an error will be
>> reported.
> 
> If you are using the filesystem then yes, errors will be reported.  dd
> does not use the filesystem.  It reads sectors directly.
> 
>> But dd isn't a good tool for creating disc images???
> 
> No.  Unless you check the logs after using dd, you may never know that
> a sector had a read error and the data it copied for that sector is
> bad.  Until you play the bit of the disk image with the error.  So use
> readom which does report errors and is designed for the job of ripping
> optical disks.

If there is an uncorrected error it is passed up the stack as a read error *on the block device* and that would get passed up to the filesystem and ultimately to the application layer. While dd doesn't use the filesystem, it will still receive errors and will abort if any are reported.
Error detection (& correction) is *NOT* a filesystem function, it is a device & device driver function.



More information about the mythtv-users mailing list