11.4 BURN-Proof Technology

Anyone who uses a CD writer has made coasters, the common term for a ruined CD-R blank. Although packet writing and UDF effectively eliminate coasters, packet-writing software is useless for batch-mode tasks, like duplicating CDs. Those tasks demand premastering software, which unfortunately is by no means immune to generating coasters.

Until recently, CD premastering was inherently an isochronous (time-dependent) process, because data had to be delivered to the write head in a continuous stream from the time the write began until it completed. If that stream was interrupted long enough for the data stored in the writer's buffer to be exhausted—an accident called a buffer underrun—the blank was ruined. Buffer underruns were particularly common with IDE/ATAPI CD writers, although they were by no means rare even on SCSI burners.

We say until recently, because a new technology called BURN-Proof (Buffer UnderRuN-Proof), developed by Sanyo and licensed to CD writer makers, effectively makes buffer underruns a thing of the past. In simple terms, BURN-Proof turns off the writing laser when it runs out of data to write (duh), and then, when data is again available, restarts the burn exactly where it left off. In effect, BURN-Proof converts CD writing from an isochronous process to an asynchronous one.

BURN-Proof works by constantly monitoring the status of the CD writer's buffer to detect a potential buffer underrun condition. If the amount of buffered data falls to a critically low level, the BURN-Proof firmware finishes writing the current sector and then turns off the writing laser until the amount of buffered data returns to an acceptably high level. When that occurs, the BURN-Proof firmware repositions the writing laser to begin writing where it left off.

If BURN-Proof kicks in, the resulting disc is not literally identical to a disc that was written without a buffer underrun occurring. Rather than restarting the write on the sector immediately following the last sector written before the buffer underrun, BURN-Proof must leave a short gap—the length of which varies with recording speed—between the last pre-underrun and the first post-underrun data sectors. Error correction circuitry on nearly all CD drives and players eliminates this minor hiccough, but very old CD drives and players may deal with it poorly, for example, by playing back an audible pop on an audio CD burned with BURN-Proof. Note that this condition applies only if BURN-Proof kicks in during the burn. If no buffer underrun occurs during the burn, discs produced on a BURN-Proof drive are indistinguishable from those produced on any other CD writer.

Our first experience with BURN-Proof was with the superb Plextor PlexWriter 12/10/32A IDE CD writer. With standard IDE CD writers we hesitated even to move the mouse while burning. We walked softly and worried about vibration from passing trucks. But the Plextor 12/10/32A and the later 16X, 24X, and 40X PlexWriters eliminate those worries. Plextor CD writers with BURN-Proof are so robust that we successfully burned a disc from an image file on the hard drive while we were defragging that hard drive—a guaranteed way to ruin a disc with any CD writer that lacks BURN-Proof.

A write takes much longer if BURN-Proof has to kick in repeatedly, but the write does complete normally, and we have never had a problem reading the resulting discs. Unfortunately, there is no way to retrofit BURN-Proof to an existing CD writer. If you want BURN-Proof (and you should), the only way to get it is to buy a CD writer that supports it. Also, your premastering software must explicitly support BURN-Proof if it is to function. The latest versions of Easy CD, Nero Burning ROM, and other popular premastering applications include BURN-Proof support, but earlier versions may not. For more information about BURN-Proof, see http://www.sannet.ne.jp/BURN-Proof/faq/.

The success of PlexWriter drives with BURN-Proof resulted in a lot of me-too products. Nowadays, all but the least expensive CD writers come with some type of buffer underrun protection, whether the original BURN-Proof or a competing technology. Each technology has its advocates, but the truth is that any of them do pretty much the same job.