[FFmpeg-user] [offtopic] expansion of video content

[JD]

Here is the info:
# isoinfo -d dev=/dev/sr0
CD-ROM is in ISO 9660 format
System id:
Volume id: ARV_NT5.1_DES
Volume set id: UNDEFINED
Publisher id:
Data preparer id:
Application id:
Copyright File id:
Abstract File id:
Bibliographic File id:
Volume set size is: 1
Volume set sequence number is: 1
Logical block size is: 2048
Volume size is:
NO Joliet present
**BAD RRVERSION (0)
NO Rock Ridge present

Once I mount the drive:
# mount -t iso9660 /dev/sr0 /sr0
mount: /dev/sr0 is write-protected, mounting read-only
# du -sk /sr0/video_ts/
25253528        /sr0/video_ts/
Since that is in number of k's (1024 bytes)
echo  "25253528 * 1024" | bc
25859612672
25859612672

So how did a 4GB volume expand into  25GB?

if we assume that the reported volume size is 4096640  2K blocks:
4096640 * 2048 = 8389918720
Which is easily contained in a double density DVD optical medium.

Was there an mp4 compression used such that the driver
performs a conversion to VOB before handing over the data to
the user process??? Just curious!!!



On Tue, Sep 24, 2019 at 8:22 AM Ted Park <kumowoon1025 at gmail.com> wrote:

> > At anyrate, I use dd to copy the dvd to HD.
> > On HD, the size of the iso file (after copying SOME dvd's)
> > is in excess of 20GB. such as 22GB+, 26GB+...etc
> >
> > Could someone explain why this is?
> >
> > I thought dvd's have capacities of 4.7GB, 8.9GB for double density.
> > I also know about dvd's that have slightly more than 10GB capacity.
>
> dd doesn’t know about any of that. Your dvd drive might handle the copy
> protection in a way that causes this, or it might be the driver (did you
> use srX or dvd device? Might not matter)
>
> Usually you determine how many blocks you want and the block size, using
> isoinfo for example, before you dd from a cd/dvd drive so you know how big
> the image is going to be before you start. But your case is interesting,
> more often you’ll get a smaller file when content scrambling is the culprit
> due to the read erroring out along the way, is the resultant image file
> usable?
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