In the course of exploring and analyzing the impressive library of CD images curated at the Internet Archive’s Shareware CD collection, one encounters a wealth of methods for copying a complete CD image onto other media for transport. In researching the formats, I have found that many of them are native to various binary, proprietary CD programs that operate under Windows. Since I have an interest in interpreting these image formats and I would also like to do so outside of Windows, I thought to conduct a survey to determine if enough information exists to write processing tools of my own.

Remember from my Grand Unified Theory of Compact Disc that CDs, from a high enough level of software abstraction, are just strings of 2352-byte sectors broken up into tracks. The difference among various types of CDs come down to the specific meaning of these 2352 bytes.

Most imaging formats rip these strings of sectors into a giant file and then record some metadata information about the tracks and sectors.

ISO
This is perhaps the most common method for storing CD images. It’s generally only applicable to data CD-ROMs. File images generally end with a .iso extension. This refers to ISO-9660 which is the standard CD filesystem.

Sometimes, disc images ripped from other types of discs (like Xbox/360 or GameCube discs) bear the extension .iso, which is a bit of a misnomer since they aren’t formatted using the ISO-9660 filesystem. But the extension sort of stuck.

BIN / CUE
I see the BIN & CUE file format combination quite frequently. Reportedly, a program named CDRWIN deployed this format first. This format can handle a mixed mode CD (e.g., starts with a data track and is followed by a series of audio tracks), whereas ISO can only handle the data track. The BIN file contains the raw data while the CUE file is a text file that defines how the BIN file is formatted (how many bytes in a sector, how many sectors to each individual track).

CDI
This originates from a program called DiscJuggler. This is extremely prevalent in the Sega Dreamcast hobbyist community for some reason. I studied the raw hex dumps of some sample CDI files but there was no obvious data (mostly 0s). There is an open source utility called cdi2iso which is able to extract an ISO image from a CDI file. The program’s source clued me in that the metadata is actually sitting at the end of the image file. This makes sense when you consider how a ripping program needs to operate– copy tracks, sector by sector, and then do something with the metadata after the fact. Options include: 1) Write metadata at the end of the file (as seen here); 2) write metadata into a separate file (seen in other formats on this list); 3) write the data at the beginning of the file which would require a full rewrite of the entire (usually large) image file (I haven’t seen this yet).

Anyway, I believe I have enough information to write a program that can interpret a CDI file. The reason this format is favored for Dreamcast disc images is likely due to the extreme weirdness of Dreamcast discs (it’s complicated, but eventually fits into my Grand Unified Theory of CDs, if you look at it from a high level).

MDF / MDS
MDF and MDS pairs come from a program called Alcohol 120%. The MDF file has the data while the MDS file contains the metadata. The metadata is in an opaque binary format, though. Thankfully, the Wikipedia page links to a description of the format. That’s another image format down.

CCD / SUB / IMG
The CloneCD Control File is one I just ran across today thanks to a new image posted at the IA Shareware Archive (see Super Duke Volume 2). I haven’t found any definitive documentation on this, but it also doesn’t seen too complicated. The .ccd file is a text file that is pretty self-explanatory. The sample linked above, however, only has a .ccd file and a .sub file. I’m led to believe that the .sub file contains subchannel information while a .img file is supposed to contain the binary data. So this rip might be incomplete (nope, the .img file is on the page, in the sidebar; thanks to Phil in the comments for pointing this out). The .sub file is a bit short compared to the Archive’s description of the disc’s contents (only about 4.6 MB of data) and when I briefly scrolled through, it didn’t look like it contains any real computer data. So it probably is just the disc’s subchannel data (something I glossed over in my Grand Unified Theory).

CSO
I have dealt with the CISO (compressed ISO) format before. It’s basically the same as a .iso file described above except that each individual 2048-byte data sector is compressed using zlib. The format boasts up to 9 compression levels, which shouldn’t be a big surprise since that correlates to zlib’s own compression tiers.

Others
Wikipedia has a category for optical disc image formats. Of course, there are numerous others. However, I haven’t encountered them in the wild for the purpose of broad image distribution.

The feature requests for my game music appreciation website project continue to pour in. Many of them take the form of “please add player support for system XYZ and the chiptune library to go with it.” Most of these requests are A) plausible, and B) in process. I have also received recommendations for UI improvements which I take under consideration. Then there are the numerous requests to port everything from Native Client to JavaScript so that it will work everywhere, even on mobile, a notion which might take a separate post to debunk entirely.

But here’s an interesting request about which I would like to speculate: Automatically convert a chiptune into a MIDI file. I immediately wanted to dismiss it as impossible or highly implausible. But, as is my habit, I started pondering the concept a little more carefully and decided that there’s an outside chance of getting some part of the idea to work.

Intro to MIDI
MIDI stands for Musical Instrument Digital Interface. It’s a standard musical interchange format and allows music instruments and computers to exchange musical information. The file interchange format bears the extension .mid and contains a sequence of numbers that translate into commands separated by time deltas. E.g.: turn key on (this note, this velocity); wait x ticks; turn key off; wait y ticks; etc. I’m vastly oversimplifying, as usual.

MIDI fascinated me back in the days of dialup internet and discrete sound cards (see also my write-up on the Gravis Ultrasound). Typical song-length MIDI files often ranged from a few kilobytes to a few 10s of kilobytes. They were significantly smaller than the MOD et al. family of tracker music formats mostly by virtue of the fact that MIDI files aren’t burdened by transporting digital audio samples.
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Throughout my own life, I have often observed that my own sense of nostalgia has a window that stretches about 10-15 years past from the current moment. Earlier this year, I discovered the show “Alias” and watched through the entire series thanks to Amazon Prime Instant Video (to be fair, I sort of skimmed the fifth and final season which I found to be horribly dull, or maybe franchise fatigue had set in). The show originally aired from 2001-2006 so I found that it fit well within the aforementioned nostalgia window.

But what was it, exactly, about the show that triggered nostalgia? The computers, of course! The show revolved around spies and espionage and cutting-edge technology necessarily played a role. The production designer for the series must have decided that Unix/Linux == awesome hacking and so many screenshots featured Linux.

Since this is still nominally a multimedia blog, I’ll start of the screenshot recon with an old multimedia player. Here is a vintage Mac OS desktop running an ancient web browser (probably Netscape) that’s playing a full-window video (probably QuickTime embedded directly into the browser).

Click for larger image

Let’s jump right into the Linux side of things. This screenshot makes me particularly sentimental since this is exactly what a stock Linux/KDE desktop looked like circa 2001-2003 and is more or less what I would have worked with on my home computer at the time:

Click for larger image

Studying that screenshot, we see that the user logs in as root, even to the desktop environment. Poor security practice; I would expect better from a bunch of spooks.

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I visited an Applebee’s restaurant this past weekend. The first thing I spied was a family at a table with what looked like a 7-inch tablet. It’s not an uncommon sight. However, as I moved through the restaurant, I noticed that every single table was equipped with such a tablet. It looked like this:

For a computer nerd like me, you could probably guess that I was be far more interested in this gadget than the cuisine. The thing said “Presto” on the front and “Elacarte” on the back. Putting this together, we get the website of Elacarte, the purveyors of this restaurant tablet technology. Months after the iPad was released on 2010, I remember stories about high-end restaurants showing their wine list via iPads. This tablet goes well beyond that.

How was it? Well, confusing, mostly. The hostess told us we could order through the tablet or through her. Since we already knew what we wanted, she just manually took our order and presumably entered it into the system. So, right away, the question is: Do we order through a human or through a computer? Or a combination? Do we have to use the tablet if we don’t want to?

Hardware
When picking up the tablet, it’s hard not to notice that it is very heavy. At first, I suspected that it was deliberately weighted down as some minor attempt at an anti-theft measure. But then I remembered what I know about power budgets of phones and tablets– powering the screen accounts for much of the battery usage. I realized that this device needs to drive the screen for about 14 continuous hours each day. I.e., the weight must come from a massive battery.

The screen is good. It’s a capacitive touchscreen, so nice and responsive. When I first spied the device, I felt certain it would be a resistive touchscreen (which is more accurately called a touch-and-press-down screen). There is an AC adapter on the side of the tablet. This is the only interface to the device:

That looks to me like an internal SATA connector (different from an eSATA connector). Foolishly, I didn’t have a SATA cable on me so I couldn’t verify.

User Interface
The interface options are: Order, Games, Neighborhood, and Pay. One big benefit of accessing the menu through the Order option is that each menu item can have a picture. For people who order more by picture than text description, this is useful. Rather, it would be, if more items had pictures. I’m not sure there were more pictures than seen in the print menu.
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Valve recently released the final, public version of their Steam client for Linux, and the Linux world rejoiced. At least, it probably did. The announcement was 2 weeks ago on Valentine’s Day and I had other things on my mind, so I missed any fanfare. When framed in this manner, the announcement timing becomes suspect– it’s as though Linux enthusiasts would have plenty of time that day or something.

Taming the Frontier
Speculation about a Linux Steam client had been kicking around for nearly as long as Steam has existed. However, sometime last year, the rumors became more substantive.

I naturally wondered how to port something like Steam to Linux. I have some experience with trying to make a necessarily binary-only program that runs on Linux. I’m fairly well-versed in the assorted technical challenges that one might face when attempting such a feat. Because of this, whenever I hear rumors that a company might be entertaining the notion of porting a major piece of proprietary software to Linux, my instinctive reflex is, “What?! Why, you fools?! Save yourselves!”

At least, that’s how it used to be. The proposal of developing a proprietary binary for Linux has been rendered considerably less insane by a few developments, for example:

1. The rise of Ubuntu Linux as a quasi de facto standard for desktop Linux computing
2. The increasing homogeneity in personal desktop computing technology

What I would like to know is how the Steam client runs on Linux. Does it rely on any libraries being present on the system? Or does it bring its own? The latter is a trick that proprietary programs can use– transport all of the shared libraries that the main program binary depends upon, install them someplace out of the way on the filesystem, probably in /opt, and then make the main program a shell script which sets a preload path to rely on the known quantity libraries instead of the copies already on the system.

Downloading and Installing the Client
For this exercise, I installed x86_64 desktop Ubuntu 12.04 Linux on a l33t gaming rig that was totally top of the line about 5 years ago, and that someone didn’t want anymore and handed down to me recently. So it should be ideal for this project.

At first, I was blown away– the Linux client is in a .deb package that is less than 2 MB large. I unpacked the steam.deb file and found a bunch of support libraries — mostly X11 and standard C/C++ runtimes. Just as I suspected. Still, I can’t believe how small the thing is. However, my amazement quickly abated when I actually ran Steam and saw this:

So it turns out steam.db is just the installer program which immediately proceeds to download an additional 160+ MB of data. So there’s actually a lot more information to possibly sift through.
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This is something I started writing about a decade ago (and I almost certainly have some of it wrong), back when compact discs still had a fair amount of relevance. Back around 2002, after a few years investigating multimedia technology, I took an interest in compact discs of all sorts. Even though there may seem to be a wide range of CD types, I generally found that they’re all fundamentally the same. I thought I would finally publishing something, incomplete though it may be.

Physical Perspective
There are a lot of ways to look at a compact disc. First, there’s the physical format, where a laser detects where pits/grooves have disturbed the smooth surface (a.k.a. lands). A lot of technical descriptions claim that these lands and pits on a CD correspond to ones and zeros. That’s not actually true, but you have to decide what level of abstraction you care about, and that abstraction is good enough if you only care about the discs from a software perspective.

Grand Unified Theory (Software Perspective)
Looking at a disc from a software perspective, I have generally found it useful to view a CD as a combination of a 2 main components:

• table of contents (TOC)
• a long string of sectors, each of which is 2352 bytes long

I like to believe that’s pretty much all there is to it. All of the information on a CD is stored as a string of sectors that might be chopped up into a series of anywhere from 1-99 individual tracks. The exact sector locations where these individual tracks begin are defined in the TOC.

Audio CDs (CD-DA / Red Book)
The initial purpose for the compact disc was to store digital audio. The strange sector size of 2352 bytes is an artifact of this original charter. “CD quality audio”, as any multimedia nerd knows, is formally defined as stereo PCM samples that are each 16 bits wide and played at a frequency of 44100 Hz.
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During my recent effort to force myself to understand Unicode and modern text encoding/processing, I was reminded that this is something that “every programmer should just know”, an idea that comes up every so often, usually in relation to a subject in which the speaker is already an expert. One of the most absurd examples I ever witnessed was a blog post along the lines of “What every working programmer ought to know about [some very specific niche of enterprise-level Java programming]“. I remember reading through the article and recognizing that I had almost no knowledge of the material. Disturbing, since I am demonstrably a “working programmer”.

For fun, I queried the googles on the matter of what ever programmer ought to know.

Specific Topics
Here is what every programmer should know about: Unicode, time, memory (simple), memory (extremely in-depth), regular expressions, search engine optimization, floating point, security, basic number theory, race conditions, managed C++, VIM commands, distributed systems, object-oriented design, latency numbers, rate monotonic algorithm, merging branches in Mercurial, classes of algorithms, and human names.

Broader Topics
20 subjects every programmer should know, 97 things every programmer should know, 12 things every programmer should know, things every programmer should know (27 items), 10 papers every programmer should read at least twice, 10 things every programmer should know for their first job.

Meanwhile, I remain fond of this xkcd comic whose mouseover text describes all that a person genuinely needs to know. Still, the new year is upon us, a time when people often make commitments to bettering themselves, and it couldn’t hurt (much) to at least skim some of the lists and find out what you never knew that you never knew.

What About Multimedia?
Reading the foregoing (or the titles of the foregoing pieces), I naturally wonder if I should write something about what every programmer should know about multimedia. I think it would look something like a multimedia programming FAQ. These are some items that I can think of:

1. YUV: The other colorspace (since most programmers are only familiar with RGB and have no idea what to make of the YUV that comes out of most video decoding APIs)
2. Why you can’t easily seek randomly to any specific frame in a video file (keyframe/interframe discussion and their implications)
3. Understand your platform before endeavoring to implement multimedia software (modern platforms, particularly mobile platforms, probably provide everything you need in the native APIs and there is likely little reason to compile libavcodec for the platform)
4. Difference between containers and codecs (longstanding item, but I would argue it’s less relevant these days due to standardization on the MPEG — MP4/H.264/AAC — stack)
5. What counts as a multimedia standard in this day and age (comparing the foregoing MPEG stack with the WebM/VP8/Vorbis stack)
6. Trade-offs to consider when engineering a multimedia solution
7. Optimization doesn’t always work the way you think it does (not everything touted as a massive speed-up in the world of computing — whether it be multithreaded CPUs, GPGPUs, new SIMD instruction sets — will necessarily be applicable to multimedia processing)
8. A practical guide to legal issues would not be amiss
9. ???

What other items count as “something multimedia-related that every programmer should know”?

Tangential to multimedia hacking is proper metadata handling. Recently, I have gathered an interest in processing a large corpus of multimedia files which are likely to contain metadata strings which do not fall into the lower ASCII set. This is significant because the lower ASCII set intersects perfectly with my own programming comfort zone. Indeed, all of my programming life, I have insisted on covering my ears and loudly asserting “LA LA LA LA LA! ALL TEXT EVERYWHERE IS ASCII!” I suspect I’m not alone in this.

Thus, I took this as an opportunity to conquer my longstanding fear of Unicode. I developed a self-learning course comprised of a series of exercises which add up to this diagram:

Part 1: Understanding Text Encoding
Python has regular strings by default and then it has Unicode strings. The latter are prefixed by the letter ‘u’. This is what ‘ö’ looks like encoded in each type.

A large part of my frustration with Unicode comes from Python yelling at me about UnicodeDecodeErrors and an inability to handle the number 0xc3 for some reason. This usually comes when I’m trying to wrap my head around an unrelated problem and don’t care to get sidetracked by text encoding issues. However, when I studied the above output, I finally understood where the 0xc3 comes from. I just didn’t understand what the encoding represents exactly.
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I have been working on adding support for SID files — the music format for the Commodore 64 — to the game music website for awhile. I feel a bit out of my element since I’m not that familiar with the C64. But why should I let that slow me down? Allow me to go through the steps I have previously outlined in order to make this happen.

I need to know what picture should represent the system in the search results page. The foregoing picture should be fine, but I’m getting way ahead of myself.

Phase 1 is finding adequate player software. The most venerable contender in this arena is libsidplay, or so I first thought. It turns out that there’s libsidplay (originally hosted at Geocities, apparently, and no longer on the net) and also libsidplay2. Both are kind of old (libsidplay2 was last updated in 2004). I tried to compile libsidplay2 and the C++ didn’t agree with current version of g++.

However, a recent effort named libsidplayfp is carrying on the SID emulation tradition. It works rather well, notwithstanding the fact that compiling the entire library has a habit of apparently hanging the Linux VM where I develop this stuff.

Phase 2 is to develop a testbench app around the playback library. With the help of the libsidplayfp library maintainers, I accomplished this. The testbench app consistently requires about 15% of a single core of a fairly powerful Core i7. So I look forward to recommendations that I port that playback library to pure JavaScript.

Phase 3 is plug into the web player. I haven’t worked on this yet. I’m confident that this will work since phase 2 worked (plus, I have a plan to combine phases 2 and 3).

One interesting issue that has arisen is that proper operation of libsidplayfp requires that 3 C64 ROM files be present (the, ahem, KERNAL, BASIC interpreter, and character generator). While these are copyrighted ROMs, they are easily obtainable on the internet. The goal of my project is to eliminate as much friction as possible for enjoying these old tunes. To that end, I will just bake the ROM files directly into the player.

Phase 4 is collecting a SID song corpus. This is the simplest part of the whole process thanks to the remarkable curation efforts of the High Voltage SID Collection (HVSC). Anyone can download a giant archive of every known SID file. So that’s a done deal.

Or is it? One small issue is that I was hoping that the first iteration of my game music website would focus on, well, game music. There is a lot of music in the HVSC that are original compositions or come from demos. The way that the archive is organized makes it difficult to automatically discern whether a particular SID file comes from a game or not.

Phase 5 is munging the metadata. The good news here is that the files have the metadata built in. The not-so-great news is that there isn’t quite as much as I might like. Each file is tagged with title, author, and publisher/copyright. If there is more than one song in a file, they all have the same metadata. Fortunately, if I can import them all into my game music database, there is an opportunity to add a lot more metadata.

Further, there is no play length metadata for these files. This means I will need to set each to a default length like 2 minutes and do something like I did before in order to automatically determine if any songs terminate sooner.

Oddly, the issue I’m most concerned about is character encoding. This is the first project for which I’m making certain that I understand character encoding since I can’t reasonably get away with assuming that everything is ASCII. So far, based on the random sampling of SID files I have checked, there is a good chance of encountering metadata strings with characters that are not in the lower ASCII set. From what I have observed, these characters map to Unicode code points. So I finally get to learn about manipulating strings in such a way that it preserves the character encoding. At the very least, I need Python to rip the strings out of the binary SID files and make sure the Unicode remains intact while being inserted into an SQLite3 database.

I’ve been rather despondent all week. People who see me daily could readily identify this fact. Unfortunately, the exact reason was difficult to adequately explain. The problems that nerds deal with…

When A Domain Expires
As a few people noticed, the multimedia.cx domain and all of it’s subdomains didn’t work this last week. The problem started on Monday, October 1. Whose fault? Well, fundamentally, I neglected to renew the domain name in time. However, I prefer to place the blame on the .cx domain registrar, CoCCA Registry. You see, they have never developed the technology to email a domain holder with a notice that their domain is about to expire or has already expired.

This domain is the only one I have ever held so I don’t have a lot of experience in this matter. I wondered if I was crazy for thinking it would be normal for a registrar to send an email or 2 with status updates about your domain. I get the impression from speaking with others that this is indeed normal. I have 3 different email addresses listed under my account at the registrar– 2 at multimedia.cx and a backup gmail account. I checked spam folders after this incident. Then I remembered that I have never received any email notifications from them (although password reset emails show up, so that part thankfully works). Also, their support emails are black holes.

So, I guess the moral is: be wary of dealing with CoCCA Registry. However, they seem to be the only way to register domains under a wide variety of uncommon country codes.

By Friday, the domain appeared to have been reinstated, even through the status was officially listed as “renewal-pending” according to the web-based management console. Eventually, as cached DNS results started to time out throughout the day, I started seeing subdomains come back. I excitedly used the ‘dig’ command to count down the seconds until gamemusic.multimedia.cx was accessible on the network I was on (the number after the domain name is the time-to-live or ‘TTL’ value):

$ dig +nocmd gamemusic.multimedia.cx +noall +answer
gamemusic.multimedia.cx. 3      IN      A       174.143.152.251
$ dig +nocmd gamemusic.multimedia.cx +noall +answer
gamemusic.multimedia.cx. 2      IN      A       174.143.152.251
$ dig +nocmd gamemusic.multimedia.cx +noall +answer
gamemusic.multimedia.cx. 1      IN      A       174.143.152.251
$ dig +nocmd gamemusic.multimedia.cx +noall +answer
gamemusic.multimedia.cx. 12962  IN      A       207.45.186.114

Finally, today (Saturday), I received a receipt confirming that the domain has been renewed.

8 Years Old
Incidentally, happy eighth birthday to multimedia.cx. It was September, 2004 when I decided to branch out from a simple ISP-based web presence.

People often ask why I went with the .cx TLD. When I decided I wanted a proper domain name 8 years ago, I found that multimedia.X was already taken for just about every TLD value of X. .cx was a notable exception and was distinctive enough (speaking of .X, though, I see that multimedia.xxx is still up for grabs as of this writing; I imagine that would come with a whole other set of problems).

It’s funny that tech nerds often rail against outsourcing too much — email, storage, computing power, web hosting — all to some type of cloud provider under the premise that it could easily be taken away. But this episode teaches me that even having your own domain name is no guarantee of a solid online presence.

Meanwhile, I have taken proactive steps to avert this same situation from arising again:

Barring a lack of automated emails from the registrar, I hope a Google Calendar reminder set up a month ahead of expiration will do the trick.