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Could CDRW Disks Replace Videotapes?
NewtonsLaw asks: "I'm in the process of building a TiVo-like PC that uses off-the-shelf technology to implement video timeshift, MPEG recording, MP3 recording, etc along with Net-radio functionality. Over the past two months I've effectively replaced VHS video tapes with CDRW disks. Once a program has been captured on the PC in (S)VCD MPEG format, I can either watch it by playing back the recorded file or dump it onto a CDRW and watch it on my DVD player, before blanking the disk and returning it to the 'empty' pile. What I've noticed is that most of the CDRWs I've tried only last about 30-40 rewrites before they start showing significant data dropouts (almost always at the start of a recording). Since disks in (S)VCD format don't carry the same level of error-checking/correction as disks written in regular data format, such dropouts are more noticeable than they would otherwise be (of course the up-side is that you get to store 805MB on a 700MB CDR/RW without overburn).
What I want to know is -- how many rewrites do most people expect from their CDRW media? I seem to recall seeing a figure of a thousand rewrite cycles being touted by some manufacturers. Is this realistic? Thirty rewrites makes a $2.50 RW disk an economic medium for this purpose but it seems a hell of a long way short of 1,000."
"I've tried CDRW disks from several manufacturers and they're being used in a new Sony CDRW drive which seems to function just fine. I've also encountered a slightly shorter lifetime for CDRW media when used for (S)VCD disks and written by a slightly older HP CDR/RW drive.
And before anyone asks 'Why don't you just play directly from the HD?', I should point out that I have to share the TV gear in this house with the rest of the family so it's just easier to burn their stuff to disk and let them use the DVD player than to fight over access to the TiVo-clone."
If I remember correctly, the CD-RW blanks I have at home (14x compatable) say they are "guaranteed" for 100 re-writes.
Also, what speed are you burning on these CD-RW's at? Maybe you should try lowering the recording speed and seeing if you still get the drop outs.
Not All Who Wander Are Lost
Even with normal data, the samsung burner, made the CDRWs I used lose data already after 4-5 burns. I think for permanent storage, normal CDr's are good, but I wouldn't trust CDRWs too much with any of my computer data or audio/video.
http://www.inspirelight.net/
Typicly I will reuse my CDRW disks arround 10 -> 15 time, but im storeing my programs, mp3 backups, and web dev work... so once its backed up to my satisfaction... I stop...
:)
Personaly I think that to acheve 30 -40 rewrites to a VCD disk with no real loss in quality beats the shit out of a VCR which you only really get 4-5 rewrites out of before you start noticeing quality issues...
Keep up the good work, and keep us informed as to when we can buy the set top version of your system
The Code Ninja is swift with his tool, precise in his delivery, and deadly accurate in his execution.
...From various places. I have a low-end P3550 and a video out-card hooked into my home entertainment system. CDR and CDRW has all but replaced VHS for me.
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This is an ongoing discussion at Plasma. People with the bucks have been contemplating this for a while. Be sure to read up on the forums for the technical details as well. More info here.
Please note there are solutions that require money. How cheap are you going to be?
If we don't fight for ourselves no one will.
A good place to learn how to convert various media to burnable (S)VCD format can be found at http://www.vcdhelp.com
Normally that would be humurous, but it's quite possible.
Who said anything about quality? :)
For one-off uses like this, generic CD-Rs should be sufficient. I can usually get a 50-pack for $5 or a 100-pack for $8-$10 -- after rebates -- once or twice a month from CompUSA or Circuit City -- the CC 100 packs are frequently even non-generic, such as Fuji.
As far as generics go, I've only had one disk ever fail on me, and that was during the write process.
Prices vary a lot, but there's often a sale for $7 per 50 CD-Rs.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Ah, but there really is a TiVo clone in the works: FreeVo.
The roots of education are bitter, but the fruit is sweet.
--Aristotle
Best Buy sells 100-paks of Memorex for $30, with a $20 rebate. I've successfully gotten all my rebates back in 1.5 months.
That comes to $5 for 50.
I built a similar system myself, basicly a tivo built out of a shuttle SS51G and a all-in-wonder. The problem I've foud is that the CDRW is just too small to replace a VHS. A MPG and standrard VCD quality is about 600 MB per hour, so a CDRW only holds an hour of TV per CD. Thats great for 1 hour long show but it doesn't work too well when you want to store a movie or a longer show. Also I mainly store serries of shows (like star trek) , its far better to have a dvd+r with several episodes of the same show then have to swap through many cds.
Here are my notes about how I made one disc:
I wondered if I got some quality degradation by exporting from MA in motion-JPEG format, rather than keeping it in native DV format, and then encoding to MPEG. Ideally some of the JPEG frames would just directly become keyframes in the MPEG output; but in this case I was scaling too, so that's not possible. Anyway most of the output formats in MainActor for Linux have bugs, and MJPEG happened to work well.
analog video "lines" and lines of digital resolution are two different things, alas.
When someone talks about lines of VHS, they're talking about how many discreet changes in amplitude you'll be able to measure on a horizontal line. And when digital video talks about lines, it's normally how many pixels high the video is.
And due to Nyquist, we know the sampling rate required to record a given frequncy is twice the frequency.
So, MPEG-1 NTSC VCD at 352 pixels wide could reproduce a frequency of 176 changes over the horizontal width of the video. So, if VHS is 250 lines, it's actually better on that measure than VCD.
Of course, VHS is plauged by horrible analog noise to the point where I can't watch it, while VCD, although low resolution, shouldn't have any noise at all. There will be some artifacts at VCD data rates, of course.
My video compression blog
VHS has a ton of analog noise. This means that you'll need to encode the digital copy at a substantially higher data rate to get the same effective quality, and you'll have a pretty low ceiling on maximum quality.
The difference between even S-VHS and VHS is huge.
So, grabbing off DVD or straight from a high-bitrate PVR would be quite a bit better. And if you have to go through analog, make sure you're capturing via S-Video instead of composite. Otherwise areas of saturated color will get that annoying cross-hatching effect. It's isn't so noticible on TV, but man is it obvious on a computer monitor!
My video compression blog
Try this link.
;-)
I'm planning to update the site with all my latest findings later this week -- including a review of a Haupaugge tuner/capture card that has onboard hardware MPEG1/MPEG2 encoding.
Linux-based options are also being reviewed as I type this