On Sun, 2022-12-18 at 19:18 -0500, Bill Cunningham wrote:
Too answer many people's questions here, as to what I want to
accomplish; is there some way to make these huge 7 GB ISOs smaller?
Are you trying to squish a double-sided DVD onto a single-sided DVD and
play it in a DVD player?
Are you trying to do something like turn a movie from a DVD into a MP4
file that you're not going to play from a DVD disc? (Files on your
hard drive, on a USB flash drive, etc.)
Converting to an mp4 would be the simple answer, but not a simple
task
as I am finding.
Handbrake for a GUI tool, ffmpeg for a command line, those are two that
spring to mind. Not that I'm familiar with either of them, it's such a
rarity that I'd have to figure it out each time.
In the dim and distant past, I'd used Nero (disc burning software) to
create a DVD disc from files meant to go on them. Just start a DVD
project, drop in your source files, and it'd do all the hard work for
you.
In recent times, I'd shoot video, import the clips into FCP (Final Cut
Pro) on a Mac, edit things together with FCP (that's it's actual
purpose, video editing), and export a file ready to burn to a DVD. FCP
did all the hard work for me.
There is some manual way I came across having something
to do with cat'ing a VOB and that somehow shrinks it.
Cat will just join files together, the program name comes from
concatenate. Sure, we often just use it to read a text file, but it's
really just dumping the text file to the screen (file[s] in, something
out in one big chunk).
cat file1 file2 file3 > joinedfile
or
cat files* > joinedfile
You'd have done some double process: Join all the source files
together, re-encode and compress them. But even that's probably not
necessary, the encoder could probably just be given a list of files to
use as an input.
Similar to the cat example, above.
I also would like to understand this ISO and dvd format much more,
as you seem to.
We've explained the files on a DVD disc, what each one is. There's
plenty of articles describing the same thing.
An ISO file is just a dump of the disc contents. If you took a DVD
disc and used dd to dump everything on it to a file, that's an ISO
file. It's an image of the contents of the disc. Virtually the same
thing as stamping vinyl records.
dd if=/dev/dvdrom of=image.iso
If you were to analyse the ISO file, you'd get the headers at the start
that define the disc, then the file system that was on the disc.
It's the same as dumping an image of a hard drive to a file. But what
makes an ISO file different is that it's the structure of an optical
disc's filesystem (CD or DVD) rather than some other medium. That
structure is ISO 9660 (the 9660 specification from the International
Organization for Standardization).
If you dumped the structure of a hard drive, it might be the partition
headers and filing system of ext3.
https://en.wikipedia.org/wiki/Optical_disc_image
https://en.wikipedia.org/wiki/ISO_9660
https://en.wikipedia.org/wiki/Universal_Disk_Format
DVDs were supposed to be UDF, which is essentially more features added
to the old CDROM way of doing things. Mostly unneeded (considering all
the do is play video), so most DVDs aren't really UDF. You'll notice
that DVDs are all upper case filenames, short length filenames, like
FAT. If they'd always used UDF they wouldn't have to constrained
themselves to those limitations. But a DVD player doesn't need human-
friendly filenames. And commercially pressed discs didn't need the
other features UDF could offer, either (multi-session, being able to
add more things to a disc, etc).
It's a bit like ASCII still living on in 7-bit plaintext emails. Most
of what we type can be covered by it, so the email client uses the
lowest common denominator, rather than always using UTF-8, only
switching over to the higher ability UTF-8 when you type something that
needs it.
--
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