MiniDVD / DVD on a CDR

[Ghrak]

This is just a quick note to help clarify some questions I keep seeing about authoring DVD video on standard CDR’s. (aka MiniDVD) It’s for the “laymen” out there.

One thing that I think hasn’t been explained clearly for us laymen is why most DVD machines can’t use CDR’s for DVD video. The problem has to do with bitrate. That is, how fast data can be supplied to the processing components in the DVD player. In order to watch a DVD movie, a massive amount of data has to be supplied from the media (DVD Disc) to the decoder/player. Now, a DVD disc puts a LOT of data into a very small space. It’s physically the same size as a CD-Rom, but holds many times the amount of information.

Because a DVD disc has so much more information in the same amount of space, the drive only has to spin the disc a little bit in order to get a lot of information. A CDR has to spin much more in order to get the same information, because it’s not as compressed. So, in order to provide the same rate of information to the processor, a CDR would have to spin much, much faster than a DVD disc. Most DVD players only spin the DVD at 2x speed, and can’t speed it up to compensate for the lower density of data on a CDR. Hence, most DVD players can’t read a CDR as a DVD even if it has the same data on it as a DVD would.

[rkr1958]

I've been very successful at making mini-DVDs that play very well in my Apex-1500 player. I found; however, that I need to set the bit rate to 4500 kbits/sec instead of the default 6000 kbits/sec when rendering my movie to MPEG-2 using Studio DV 1.10. On created, I just burn the MPEG-2 file to a CD-R and it plays great. I've been very happy with the results.

[Kdiddy]

Most DVD players only spin the DVD at 2x speed, and can’t speed it up to compensate for the lower density of data on a CDR. Hence, most DVD players can’t read a CDR as a DVD even if it has the same data on it as a DVD would.

While most of what you say is correct, the above is not. The reason most players do not read CDR/Ws with DVD author material is simply a matter of firmware programming within the player. The player reads the first sectors of media to determine what type of media is present. When a CDR/RW media is detected, the firmware was been program to recognize CD Audio, mp3, or VCD/SVCD, not DVD authored material.

The drive speeds is not truly a factor. Meaning, that anyone who will want to make a miniDVD will want truly more than 15 mins of video per disk. I use to make miniDVDs with the video around SVCD standards (~2 mbps). Thus fitting more video per disk, which worked fine. onmy player that reads miniDVDs. However, when you take that same disk to a machine that say plays SVCDs, it will not play because of how the disk is authored NOT because of the bitrate.

[kinneera]

Both explanations given are correct if you are using DVD bitrates on your miniDVD.

[Ghrak]

Thanks for clearing that up! I'm the first to admit that I fall under the banner of "Layman" so my technical knowledge here is very limited. I was just trying to sum up what I had kind of garnered from other posts... :wink:

[rkr1958]

Bit Rate does affect how well a miniDVD plays. When I authored at higher than 4500 kbits/sec; e.g., 6000 kbits/sec which is the default for DVD Quality (at least in SDV 1.10), the video shutters. Also, I noticed that when I play a miniDVD authored at the 6000 kbits/sec on my computer through my DVD-ROM drive I also encounter shutters, but the same disc plays great when I play in through my CD-RW, which spins at a max rate of 32x. Therefore, and as a layperson, I came to the same conclusion as Ghrak that DVD players cannot spin CD-Rs fast enough to play MPEG-2 movies authored at the higher bit rates.

[Kdiddy]

Again, lower the video bitrate to SVCD standard 2.5 mbps or VCD standard of 1.15 mbps, and author as DVD, it will still not play because of firmware. The firmware in a standalone DVD player is checked before you would ever push play to see if the bitrate was too high.

[rkr1958]

I have an Apex 1500 DVD player. It plays CD-Rs. It'll play any MPEG-2 file, regardless of bit rate, that I've burner to the CD-R. I've found that bit rates higher than 4500 kbits/sec produces a shutter effect. Apparently there is no firmware in my player that limits playing CD-Rs. In my opinion the shutter at bit rates > 4500 kbits/sec results from the DVD player being not able to spin the CD-R fast enough.

[Ghrak]

So has anyone ever heard of a way around the firmware media detection? Is there some way to burn a CDR that would "fool" the machine into thinking it was DVD media? A hack perhaps for a DVD player? If not, is there a list of players that don't detect media? (Like that Apex one?)

[Ghrak]

(Er, ignore the list part of my last post. I really should have looked at the DVD Player list first...)

[resnullius]

Kdiddy is right,
It has nothig to do with the speed it goes... it's all in the firmware. the best comparison would be a 60 min tape and a 120min tape that are the same size, the 120min tape is thinner and so can store more info...

[Kdiddy]

rkr1958: I never said your player in particular, I said "most" players. My player GE1101P, accepts the firmware hack used on some apex machines that will allow for miniDVD usage. Apex, Daewoo, & GE are the only "popular" models that I know both with & without hacks that allow for miniDVD usage. These manufactuers hardly represent the lion share of the market when it comes to DVD players. Dont get me wrong, Im not downing miniDVD, I was all for it at first, I loved the idea of keeping the 5.1 audio. But when I took a closer look, and realized that for my DVD ripping purposes and keep the # of disks to around 2 disks per movie. I was sacrificing an average of 600 kbps from my video. I soon decided that Id rather watch a rip with an average video bitrate around 2.2 mbps with very good dolby surround, than average bitrate of 1.6 mbps with 5.1 audio. But that was just my personal choice.

[kinneera]

It has nothig to do with the speed it goes... it's all in the firmware. the best comparison would be a 60 min tape and a 120min tape that are the same size, the 120min tape is thinner and so can store more info...

This really isn't a correct comparison. The issue with high bitrates on a CD is absolutely one of areal data density, and thus spin speed. At 1x, data can be read from a CD at a rate of only about 150Kb/s, whereas a DVD can read about 1.38MB/s at that speed. Since most consumer standalone players have DVD drives with a maximum spin speed of 2x, they can only achieve data read speeds of approximately 300Kb/s, or about 2.3Mbps (adjust slightly higher for non-true-base2 math) from CD media, thus the bitrate maximum for SVCD.

Thus, for the majority of players, true DVD bitrates (4Mbps+) will cause failure due to the technical inability to retrieve the information at the necessary rate. At SVCD and lower bitrates, the firmware will also cause problems on most players. The intersection between those players that can handle the desired bitrate without firmware interference is quite small, thus the limited viablity of miniDVD for most people.

The tape analogy is more appropriate the the concept of overlength CDs (80, 90, 99 min), where a thinner and higher density spiral is used to achieve extra storage capacity.

[Betamax]

MiniDVD (and also gdvd) works fine on CDR. You create it like a 'plain' DVD with programs like DVDit.

Just keep in mind that this type of DVD only works on PC's. A standalone DVD will never accept this type of dvd.

[resnullius]

While i don't want to start an argument i will say this. 1st dvd reading a 1x is not the same spin speed as cd reading at 1x, 1x dvd is spinning much faster ( http://www.extremetech.com/article/0,3396,s=1038&a=5803&app=7&ap=8,00.asp ). This is how i understand it, and if someone has proof that i'm wrong ps show it i like to learn. Think of a spiral 12cm in diameter, this spiral has thick lines and therefore can only have a lengh of 1 meter(fictive number) if uncoiled. if you reduce the thickness of the line your spiral can therefore be much longer, while maintaning the same diameter.

[kinneera]

We're not disagreeing on concept so much as interpretation of the details as to why:

1st dvd reading a 1x is not the same spin speed as cd reading at 1x, 1x dvd is spinning much faster

Mechanically, 1x is 1x, whether it is CD or DVD. The difference is that as the laser passes over the same portion of the disc, it can read far more data from a DVD. This is primarily due to the fact that the pits in the disc are physically much closer together on a DVD. One way of thinking of this is to say that a DVD has much larger sectors than the 2352-byte sectors on a CD. Thus, for one complete spin, the DVD reads of 10 times as much data. In this sense, it is faster, but not because the mechanical components of the drive are spinning the disc any faster. Thus the problem when you ask the drive to read the same amount of data from a much lower density CD at the same spin speed.

The other method by which greater capacity on DVDs was achieved was indeed to make the spiral narrower. This has no bearing on the complications of spin speed when comparing CDs and DVDs, however, since the problems of variable linear velocity apply to both equally and it does not alter the mechanical aspects of spinning the disc.

If you still don't believe me, the simplest test is to author an XVCD or SVCD at an extremely high bitrate and then try to play it back on a player that you know accepts those formats (no firmware interference). Most players will choke, in the sense that you will see it attempt to load and display the video, but it will stutter and freeze constantly as it either drops frames that it couldn't read in time or waits in less-than-realtime for the disc to spin to the data before displaying it.

[resnullius]

my settop player only accepts vcds so i can't test your theory, but if you go to the link i posted earlier, they explain that even though there is more info in 1 spot on a dvd than on a cd the dvd still has to move faster than 1x cd speed to read enough info. To my understanding 1x is not a fixed value that's shared between cd and dvd as 1x is in an audio cd the speed at which the cd turns to read an audio cd in real time. The dvd has to turn faster as it has alot more info to read.
As i said b4 i'm very willing to learn, could you pls state your source so i can consult them.

[kinneera]

FYI - Your link is dead, so I haven't been able to read the article. In any case, I suspect your confusing the difficulties of CAV (constant angular velocity) vs. CLV (constant linear velocity) that all disc-based playback devices suffer from with the concept of the laypersons speed measurement (1x, 2x, etc...).

I trust you're familiar with the concept, but just for the sake of completeness I'll give the short summary. When data is read from a disc, the angular velocity is constant but not the linear velocity. Thus, inside tracks actually spin much faster from the perspective of the read head. This applies to any disc, including hard drives and even an old phonograph. Thus, a mechanical measurement of spin speed, such as 1x, has to be interpreted carefully.

Typically low-speed drives (1x - 8x) use CLV, which will actually speed or slow the spin rate of the disc to ensure a constant data rate. This means that the advertised maximum speed really is the speed at which data will be read at all times. It's a bit of a misnomer, however, since the data rate is what is being guaranteed, not the actual mechanical spin speed of the drive. Thus, you and your article are probably correct (forgive me I'm totally off-base here, as I'm operating on hypothesis here) in the sense that the DVD may read the disc faster at some times than at others. The effect will be to produce an average mechanical spin speed of 2x for most standalones. This still does nothing for the vast difference in data density between CD and DVD media.

For higher speed drives, CAV is used, so the data read speed varies widely from the inside to the outside of the disc. At this point, it is anyone's game, which is why computer DVD drives generally have no problem reading a miniDVD authored at true DVD bitrates (computer CD and DVD drives typically have a minimum linear velocity equivalent of 8x - more than enough for miniDVD. Unfortunately, very few standalone DVD players ship with "computer grade" DVD drives, so they are not as capable.

[Ghrak]

Boy, almost makes you wanna grab a 1U rack, a mobo, and build your own DVD player to run all the homebrew MiniDV's you can burn!

So, are you saying that 1x CDROM speed is not actually the same as 1x DVD speed, in terms of actual physical speed of the disc? (i.e., does 1x CD move one radian's worth in the same time as a 1x DVD?)

Or, is a 32x CD-Rom just 32x faster than the first CD-Roms, and a 2x DVD is twice as fast as the first gen DVD's? It really isn't a very useful nomenclature when you think about it. Maybe they should give us an RPM rating on these things instead. Of course, that wouldn't allow them to pad their "x" rating through other technology, like special laser heads or something. Oh well.

In conclusion, I guess I should just go look for one of those $73 Apex machines that seem to play everything you stick in em...

[Ghrak]

(p.s. - His link is dead, but the address is actually viable. It's just that the bbs program didn't recognize all the commas and stuff that were actually part of the address. Just do a cut/paste and you can see the article...)

[kinneera]

My mistake, should have looked at the URL a little more closely...

In any case, the article doesn't provide any particularly technical basis for the claim that the DVD drive has to spin faster than a CD drive. Thus, I stand by my argument that the discrepancy between data densities is the major barrier when dealing with true-DVD bitrates on CD media. (Any hypothetical increase in mechanical spin speed in a DVD player is not enough to account for the substantial disparity between the required data rates - a judgement that is born out by my experimentation with extremely high bitrate XVCD and XSVCDs).

[vitualis]

Actually kinneera, 1x DVD approximately equals 3x CD when reading a CD.

A DVD drive only capable of reading 1x DVD can thus read a CD at approx. 3x CD. This is in the DVD FAQ (don't have URL but just do a Google search).

This is generally why even a 1x DVD mechanism in a stand-alone DVD player will have no difficulty playing a stamped SVCD (which have a max. bitrate of only 2x CD).

As for why most DVD players can't play miniDVDs, I think that it has already been covered. It is a firmware issue. Once the DVD player sees that it is CD media, it won't load the DVD software.

For those that do play miniDVDs, bitrate can be a factor too. A 1x DVD drive can only read CDs up to a max. of about 3x CD. Thus, any miniDVD with a bitrate greater than approx. 2-3x CD may not be read quickly enough.

Regards.

[Baja]

You may fool some of dvd player if they are not able to play miniDVD. First create your mpeg file in DVD format then use nero to create a SVCD but do not let it re encode. If your player plays SVCD, you fool the player

[Kdiddy]

You may fool some of dvd player if they are not able to play miniDVD. First create your mpeg file in DVD format then use nero to create a SVCD but do not let it re encode. If your player plays SVCD, you fool the player

Surely if was that easy it would have been done by now, the fact that it hasn't, is proof positive that this can not be done. The reason being is that the .ac3 sound is not part of SVCD spec. The video will play, but you will not get any sound.

[heavyharmonies]

Reading this thread, I'm wondering why I'm NOT seeing a problem playing some of the video I've captured.

Video captured via ADS USB Instant DVD at 5Mb/sec CBR; resulting MPEG2 file burned to a data CDR. Plays fine in my El Cheapo Daewoo DVD player. No sign of any flickering, stuttering, etc.

-Dan

[Kdiddy]

Reading this thread, I'm wondering why I'm NOT seeing a problem playing some of the video I've captured.

well you didnt read clearly enough, for I posted:

Apex, Daewoo, & GE are the only "popular" models that I know both with & without hacks that allow for miniDVD usage.