[offtopic] expansion of video content

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[offtopic] expansion of video content

jd1008
I am at a loos what newsgroup to ask this of,
as google provided no relevant answers about
this problem.

I always back up my dvd's to HD in case they get
damaged, as I do loan them to friends sometimes.

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.

So, how is it that the iso image can get that large?

Thanx in advance.

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Re: [offtopic] expansion of video content

kumowoon1025
> 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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Re: [offtopic] expansion of video content

jd1008
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 <[hidden email]> 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?
> _______________________________________________
> ffmpeg-user mailing list
> [hidden email]
> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> [hidden email] with subject "unsubscribe".
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Re: [offtopic] expansion of video content

jd1008
In reply to this post by kumowoon1025

On 9/24/19 8:14 AM, Ted Park 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?
I should have mentioned that the resulting iso plays only partially,
that is: it (meaning VLC, mplayer, ffplay) play only the intro and stop.


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Re: [offtopic] expansion of video content

kumowoon1025
> I should have mentioned that the resulting iso plays only partially,
> that is: it (meaning VLC, mplayer, ffplay) play only the intro and stop.

Right, I’m guessing there are a lot of 0’s in there, I bet if you gzip that file it’ll turn out to be a lot smaller than the 4.7, 8.6GB or something you’d expect.


> # isoinfo -d dev=/dev/sr0
> CD-ROM is in ISO 9660 format


> 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


So I think you might have a udf only dvd mounted as iso9660.


> 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!!!

No, I think we can be pretty sure nothing like that is happening especially since that user process is dd...
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Re: [offtopic] expansion of video content

Moritz Barsnick
In reply to this post by jd1008
I may be somewhat off, but:

On Tue, Sep 24, 2019 at 11:15:39 -0600, JD wrote:

> 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:

I don't see a number here. I assume the 4096640 you quote is usually
displayed here.

> 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?

I'm guessing here, from hearsay:

The former "isoinfo" shows you the raw disk size. 8 GB sounds
reasonable, as you wrote.

The latter "du" shows you the mounted file system. The value (probably)
represents whatever ISO9660 tells the driver.

You must understand that the ISO9660 file system is an *additional*
abstraction on the DVD. A real DVD video player does not know how to
read a file system, but rather uses other raw information to access its
tracks (or whatever you want to call them) correctly. On copy-protected
(video) disks, the ISO9660 file system is a big fake to fool programs
which mount the file system. Files may appear much larger than they
should be, stuff may be hidden, sectors with I/O erros may be included,
and so on.

IMO, you need to copy your images with something which operates on the
raw device, not on the file system.

Anyone: please correct me if I'm wrong. My experience with DVDs is a
bit aged. ;-)

Cheers,
Moritz
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Re: [offtopic] expansion of video content

kumowoon1025
> You must understand that the ISO9660 file system is an *additional*
> abstraction on the DVD. A real DVD video player does not know how to
> read a file system, but rather uses other raw information to access its
> tracks (or whatever you want to call them) correctly. On copy-protected
> (video) disks, the ISO9660 file system is a big fake to fool programs
> which mount the file system. Files may appear much larger than they
> should be, stuff may be hidden, sectors with I/O erros may be included,
> and so on.
>
> IMO, you need to copy your images with something which operates on the
> raw device, not on the file system.
>
> Anyone: please correct me if I'm wrong. My experience with DVDs is a
> bit aged. ;-)

I know it is possible to have no iso9660 filesystem on a dvd at all, which might be the reason behind the lack of any info from isoinfo. Also, I agree that working on the raw device is the ideal approach to take, but in theory only. After all, OP ended up where we are now after dd copied 20+ GB’s from /dev/sr0.

DVD is proprietary and licensed in a way that drive manufacturers have to implement scrambling. It’s been broken for a while now, but if you don’t do anything to work around it, the actual block device will lie to you when asked to read from a copy protected disc.
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Re: [offtopic] expansion of video content

jd1008

On 9/25/19 8:54 AM, Ted Park wrote:

>> You must understand that the ISO9660 file system is an *additional*
>> abstraction on the DVD. A real DVD video player does not know how to
>> read a file system, but rather uses other raw information to access its
>> tracks (or whatever you want to call them) correctly. On copy-protected
>> (video) disks, the ISO9660 file system is a big fake to fool programs
>> which mount the file system. Files may appear much larger than they
>> should be, stuff may be hidden, sectors with I/O erros may be included,
>> and so on.
>>
>> IMO, you need to copy your images with something which operates on the
>> raw device, not on the file system.
>>
>> Anyone: please correct me if I'm wrong. My experience with DVDs is a
>> bit aged. ;-)
> I know it is possible to have no iso9660 filesystem on a dvd at all, which might be the reason behind the lack of any info from isoinfo. Also, I agree that working on the raw device is the ideal approach to take, but in theory only. After all, OP ended up where we are now after dd copied 20+ GB’s from /dev/sr0.
>
> DVD is proprietary and licensed in a way that drive manufacturers have to implement scrambling. It’s been broken for a while now, but if you don’t do anything to work around it, the actual block device will lie to you when asked to read from a copy protected disc.
Thank you Ted for this revelation. I had no idea .....
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