DVD Writing and Linux

Courtesy: Nitin

DVD writing under Linux has been something quite mystical to many for some time. We know many people who haven't even considered getting a DVD writer simply out of fear that they won't get much use out of it under their favorite OS. We're here to tell you that if you get use out of your CD burner then you will surely find a place for these new disks that can hold an advertised 4.7GB of data. We say advertised because that number is in base-10 units and not base-2. The actual space you can fit on a DVD+RW disk is around 4.4GB. When we started our search for DVD writing for Linux knowledge we first went to everyone's favorite search engine, Google, and searched for anything DVD and Linux related. From the list of search results we ended up at the site DVD+RW/+R/-R[W] for Linux. This site not only provides the basic information on what is required to burn data to a DVD+RW/-RW disk, but it also contains the answers to most of the questions that you could have about the DVD writing formats and other related topics. This isn't suppose to be a full DVD writing tutorial or we'd go into greater specifics but, just to let you know, both DVD+RW and DVD-RW are supported by Linux through the dvd+rw-tools. These tools include dvd+rw-format, which is what you use to initially format the DVD disk, and growisofs, which is a front-end to mkisofs, which allows you to create DVD file systems on the fly. There is a lot of information on this subject on that site and you should read enough to feel comfortable doing it yourself. For our testing, we used their methods for writing disks. The next question on your mind (or maybe it was the first) is how to burn DVD videos under Linux. It turns out that DVD video disks are just regular DVD data disks with a special format and directory structure. They are based on the UDF file system and require special files in the correct places so that DVD-ROM players can access them. The best source for this information that we could find was a set of utilities/scripts that a guy is working on to automate the process of creating a DVD from MPEG files under Linux. These utilities, collectively called dvdauthor, are still a little rough, but they should get you started on your way to authoring DVD video from Linux. We'll share our results later in this article. The LDW-401S LDW-401S Box Front      LDW-401S Box Back Lite-On's entry into the DVD writing market is in line with other drives you will find on the market and boasts 4x4x12+40x24x40 speeds (DVD+R x DVD+RW x DVD Read + CD+R x CD+RW x CD Read). Here are the specs from Lite-On's web site: Speeds:      DVD Writing (DVD+R):      4x (5400KB/sec) CLV DVD Rewriting (DVD+RW):      4x (5400KB/sec) CLV DVD Reading (DVD-ROM):      (single layer) 12x (16200KB/sec) maximum by CAV (dual layer) 8x (10800KB/sec) maximum by CAV (DVD+RW) 6X(8100KB/sec) maximum by CAV CD Writing (CD-R):      40x (6000KB/sec) maximum by P-CAV CD Rewriting (CD-RW):      24x (3600KB/sec) maximum by P-CAV in UltraSpeed disc CD Reading (CD-ROM):      40x (6000KB/sec) maximum by CAV      Access Times:      DVD:      160 ms CD:      140 ms      Buffer Size:      2MB Notice that the DVD side of the drive burns with a CLV or Constant Linear Velocity while the CDs burn with a CAV or Constant Angular Velocity. This means that DVD disks are written at the same rate across the entire disk while CDs are written as fast as the drive can spin. This should make for a more even burn on DVD disks with hopes for greater compatibility. The access times are average for a DVD burner and for maximum read performance you should think about adding a standard reader to your setup. The buffer on this drive seems a bit small at 2MB but it's fairly standard for most DVD writers and we didn't experience any buffer-underruns during our testing. Box Contents The drive comes with everything that you'll need to get it up and running, minus an IDE cable. It comes with a users manual, warranty information, two disks with Windows software, a DVD+R disk, a DVD+RW disk, a quick install guide, screws, and a CD audio cable. There's nothing more you could really want except for some Linux instructions perhaps but we haven't seen anything ship with those in quite some time. LDW-401S Front      LDW-401S Back The back of the drive is fairly standard with it's IDE port, power socket, and analog and digital audio outs. It's still nice to see that some manufacturers still include the digital output as it's not a standard feature for the industry. Testing The testing of this drive was performed on our workstation platform which included a dual Xeon 3.06GHz and 1GB PC2100 DDR memory. We wanted to use something that could power through some MPEG encoding and that wouldn't bog down on any burning chores. We are happy to report that the system was very much under-utilized for the burning chore. We saw only about 10-15% CPU utilization while writing. This means that there is a high probability that the 800MHz Pentium III that the box recommends could actually perform the burning chores without problem. For this drive we went through the standard gambit of testing for any CD-RW drive which includes a CD-ROM read test, digital audio extraction test, and both CD writing and rewriting tests. To this we added two tests to time DVD+R and DVD+RW writing. All tests were ran multiple times to get a good median speed and to make sure the drive operated without glitches. Performance The first test utilizes a utility called ZCAV which measures the read speed of a drive at given intervals across the disk. This utility can be found with the bonnie++ benchmarking package. In our test we used 10MB increments and graphed the results using gnuplot. All graphs below also include the Lite-On 52x32x52 CD-RW drive for reference. It's Lite-On's top-of-the-line CD-RW at the time of publication. This graph shows the drive performing just as advertised with a top speed of around 40x. No surprises here. The digital audio extraction test uses cdda2wav and extracts 11 tracks from a 67 minute 37 second Mozart CD. The songs are listened to for quality and the total time is recorded. Here, the LDW-401S, was able to blow away the performance of the faster 52x drive. The 52x though did have a rather slow showing but, none-the-less, the LDW did a fine job. In the next two tests we burn a 638MB RedHat 9 CD and record the writing times, fixating times, and, for CD-RW, blanking times. The image is burned with a command similar to: cdrecord -v blank=fast speed=40 dev=2,0,0 -data redhat-9-disk1.iso We leave the “blank=fast” out for standard CD-R writing and change the speed to the drive's specified top speed. In both of the above CD writing graphs, the drive once again performs where expected in relation to the 52x writer. It does a great job of keeping up to its specs for a combo drive. Finally, we ran the DVD writing and rewriting portion of our benchmarks. For these tests we used growisofs to burn right at 4.4GB of data to both DVD+R and DVD+RW disks. The process is timed with the time command and the total time is recorded. Once again the new Lite-On burner worked almost right on spec and wrote at approximately 5.2MB per second. Both DVD+R and DVD+RW performed at this speed which means that as long as what you plan on using a player or DVD-ROM that will support the DVD+RW format, you can burn happily knowing that you won't be slowed down for the ability to rewrite a disk. Quirks, Compatibility, and Conclusions During burning we did run into two problems. The first was the occasional media sense error when trying to burn to DVD+RW. This seemed to only reveal itself after we canceled a burn and it was easily fixed by reloading the media. The other problem we ran into was when we 'Ctrl+C'ed out of a format. This was apparently a bad idea, as the drive locked up and a complete shutdown and reboot was required to unlock it. The media turned out unharmed though and we were able to continue without issue. Finally, we wanted to find out how compatible these disks were with some other DVD drives we had around. We created four disks: a DVD video DVD+R, a DVD video DVD+RW (2.4x media), a data DVD+R, and a data DVD+RW (4x media). First we wanted to see if we could play our video disks in our four year old DVD player or Xbox. Neither player recognized the disk as a DVD movie or anything else for that matter. This was a little disappointing but not completely unexpected. We probably would have had much better luck if we would have had a newer player. Next we tried all four disks in a standard 12x DVD-ROM from Sony. Three of the four disks we able to be mounted and read from without a hitch. The only disk that did not work was the DVD+RW with 4x media. We aren't sure if the drive preferred the different brand of media or the speed at which it was written. The 2.4x media was Verbatim and the 4x media was provided by Lite-On with the drive. So overall how do we feel about this drive? We think that it did a great job of living up to expectations and delivering just as advertised. All speeds were phenomenal and even the CD-R(W) speeds are nothing to laugh at. This drive could easily be the only drive in your box. The only thing we'd like to see is if a firmware update could fix our two canceled burn issues. Beyond that, we look forward to reviewing Lite-On's next drive which will be a DVD combo drive solution that will burn both DVD+R(W) and DVD-R(W) disks. We'd like to see if the DVD-R standard is more compatible with our standard players. Kudos to Lite-On for a solid drive.

 

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