Sending Hi-Res Audio via Internet

From the September 2000 issue of EQ magazine.

In the March 2000 issue of EQ, I outlined ways to boost the quality of the CDRs that you burn. Whether you mix down to 16 or 24-bit resolution, CDR is a universal interchange format for music that is sent out for mastering or replication. The right combination of burner and media can produce error rates that are very low. Even so, glitches can still crop up. I ask clients to send two copies of a premaster whenever possible.

Could there be a faster, cheaper, better way? Yup. Therein lies a story....

A client in Singapore emailed me recently. (Call him Bill.) He needed his latest album mastered ASAP. The release was behind schedule. Radio stations had already heard rough mixes and wanted the finished goods - yesterday. Was there a way to speed the process up?

I asked him two questions. Could he reliably burn CDRs? Yes. How fast was his Internet connection? Cable modem, capable of receiving an album's worth of CD-Audio in a few hours. (Good answers! We're jammin' now!)

I recommended that he use the Internet, specifically File Transfer Protocol, FTP for short, to send his original mixes to me. I would master the tracks. He could FTP them back to his computer and burn CDRs for replication and advance promo. He could also forget about Customs delays and Air-courier charges, not to mention save four days shipping. Was he interested?

Yes, but with reservations. Bill had moved MP3 files over the Web, but MP3's are not CD-quality. A master is a different story. How will FTP work? What about security? Would the music be degraded in any way?

Great set of questions! Let's break it down:

FTP is the way that files were transferred across the Internet in the '80s, before the Web existed. It is used millions of times a day because it makes the chore of sending multiple files quick and easy. Two programs are required, one on each end of the connection. They are usually referred to as the server and client.

I already had an FTP server running, connected to the Internet 24/7. An FTP server is like a simple Web server. Instead of delivering text, graphics and multimedia content in browsable hypertext format, it serves up files - and only files. You access an FTP server using an FTP client, which is the equivalent of a simple Web browser. When you start up an FTP client, it asks for the address of the server you need to access and for a login name and password. The client then connects to the server and displays two windows. One window shows the files on your computer, while the other shows files available on the server. If you double click on a filename displayed in the server window, it automatically downloads onto your machine. Double click one of your files and off it goes to the server. Or you can drag and drop files from one window to the other. That's it! Dozens of free FTP clients and servers are available for download off the Web. More on that later. Here's a screen shot of WSFTP, to show you what it looks like when you are logged into an FTP server.

FTP screen shot: CD Mastering FAQ

Security Issues

So, we can move files easily. Could someone access my FTP server, grab Bill's music, and share it for free with ten thousand close friends? Nope.

Many FTP servers encourage what are known as anonymous logins. Literally, you use the login name "anonymous", "ftp" or "default", and this grants you access to all the files that are available for download. This is the standard way that FTP servers offer files to the public. No password is required, though it is courteous to type your email address into the space reserved for a password. This allows the system administrator to see who is using their resource.

FTP sites can also be set up for tightly restricted access. You need to have the correct address, a certain login name and a specific password. Assuming the software is well designed and the person running the server is careful about selecting login names and passwords, the system will withstand concentrated attempts to break in and access restricted files. FTP has been around for a long time, and the technology is proven.

Maintaining Quality

Bill was concerned that some of his music might get lost in transit. By this time, he had already downloaded a couple of freeware FTP clients to his machine. I recommended a test: He should FTP a reference track from Singapore to my machine in scenic New Hampshire, then download it back to his computer, a round trip of 19,000 miles. Then he could compare the original and the copy. He did this, and could not detect the slightest difference. Why?

FTP has powerful error checking built into it. When a chunk of (music) data, called a packet, is transmitted, an additional code, called a CRC (cyclical redundancy check) checksum, is sent with it. When the packet reaches the destination, the FTP software uses the checksum to verify that the received data is identical to the original. If the CRC is perfect, the next packet is transmitted. If not, the software asks the sending computer to send the packet again. The CRC checksum is calculated again. The software will not report a successful transfer until every bit of data (pun intended) has checked out as perfect.

Its a Wrap

Bill was convinced. I emailed him the correct address, login name and password. He uploaded fourteen tracks. After they were mastered, I placed the finished tunes in WAV format on my server. I emailed him that the album was complete, he logged back in to the server and downloaded the entire album in less than three hours. A few hours after that he had burned multiple CDRs and the album was getting advance airplay. Everybody was happy. Time to kick back...

You need only three things to make a similar scenario work for you - a CD burner you trust, a fast Internet connection, and an FTP client. Burners often come with computer systems these days, and many do a fine job, especially if you burn at less than maximum available speed. DSL, cable modem and other fast Internet connections are becoming common today, even outside metro areas. Talk to your mastering house about the options they offer. Most can accept WAV and AIFF files, which are two common formats.

How do you select an FTP client?

There are dozens available. I use an old reliable called WS-FTP. Some people prefer CUTEFTP, which has extra features. Bill in Singapore used Leech FTP, which operates in a very cool multi-threaded way. It doesn't move your files in sequential order, it transfers them all simultaneously. I watched in amazement as my server transmitted fourteen files at the same time to the same destination. Leech FTP efficiently used every scrap of speed that my server could dish out.

What about setting up an FTP server?

There's no need to do this, unless you're interested in providing files to other people. If you do, there are many choices. The one I use is called WFTPD. Its fast, simple, secure, and inexpensive. I also have a freeware Web server, Xitami, which includes a similar FTP service (called a daemon) as part of the package. Both of these programs use few system resources. You can easily set up a fast FTP server on a slow Pentium computer. Even an old 486 system will work fine if you don't plan on having dozens of simultaneous users. The bottleneck will be your connection speed, not the processor speed. 8 or 16 mB of RAM is usually more than enough.

Paranoid about possible degradation?

Here's a neat way to verify that the files on your hard drive are perfect copies of the files that the mastering engineer created. After you download your music via FTP, grab a copy of a handy little program called CRC32. It lets you quickly generate a 32-bit CRC checksum for an entire WAV file. I use it as follows: The mastered WAV files are stored in a single directory. I go the DOS prompt, available from the Program menu in Windows, and change directory to the location of those WAV files. (If I stored them on drive M:\ for example, I use the command CD M:\) Then I type in the command CRC32 *.WAV This generates a checksum for all WAV files in this directory. I place these values in a simple Notepad text file which the client downloads along with the music. The client can use CRC32 to regenerate the checksums for the files - exactly as they sit on their hard disk, ready to burn to CDR. If the new checksums match the ones in the text file, you have a true mirror image. Changing even one sample out of the tens of millions contained in a music file will result in a radically different checksum. If you have a digital editor, download a copy of CRC32 and try it for yourself.

Paranoid about security also?

A handy utility called WINZIP allows you to password-protect a file or group of files. Even if a malicious software cracker intercepts the file in transit, they would need the password to play the music. WINZIP will also compress files so that they can be transmitted more quickly, but most music of 16-bit resolution and higher is too random in nature to benefit greatly from this type of compression.

Security-conscious folks should be aware of a "feature" of CuteFTP and many other shareware software programs: they automatically transmit information about your system, plus ad banners that you click on, back to a central database. This activity continues at least until you register (pay for) them. The term SPYWARE is often used to identify these programs. While spyware activity poses no threat to the security of your music, some people are concerned that the spyware engine itself could be hacked by experts to gain "back door" access to your computer. Check Gibson Research for more info.

Resources and Notes:

WS-FTP, CUTEFTP, WINZIP, XITAMI and tons of other software can be found at Tucows
WFTPD server software can be found at WFTPD
The Leech FTP client can be found at Leech
CRC32 can be found at Winsite, another large software site.
If you have any trouble locating a program, type it's name into a search engine such as Metacrawler. This will lead you to multiple sources for each file. If you search on "FTP FAQ", you'll find many sources of information on FTP servers and clients.
If you need super-secure file transfers, check out encryption software at Pretty Good Privacy.

Core FAQ covers analog and digital mastering, DRT's custom gear, sample tracks and pricing.
Background FAQ and Letters offer tips for making better mixes: compression, EQ, CDR issues.
Custom Service is a quick summary for people who target the Major-label market.
Tech News expands on selected technical topics.
One-Minute Tour is where most people start.