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."

Comments

I heard around "100"

[delus10n0]

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.

Re:I heard around "100"

[Sancho]

I don't know about VCD. To me, the quality just isn't there compared to a well-kept VCR. SVCD can compete with it's higher (and variable) bitrate, but then you suffer from 35minutes of video (for top quality) per disc.
If you get a DVD player that can play out of spec (S)VCDs, this can sort of change. You can up the bitrate of VCDs, and/or make them VBR to increase qulaity. You can also check out the CVD standard, which is 352x480, VBR, mpeg-2. It's a real standard, and it's only a bit off from SVCD. You save a bit ont he bits (giving you a bit more time per disc) and better yet, the valid CVD streams are completely compatible with the DVD spec, meaning if you ever get a DVD burner, the same streams will can be burned as a DVD-Video.

# of rewrites...

[dallask]

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 :)

Here is a good resource:

[Geminatron]

A good place to learn how to convert various media to burnable (S)VCD format can be found at http://www.vcdhelp.com

What about FreeVo?

[Mitchell Mebane]

Ah, but there really is a TiVo clone in the works: FreeVo.

Re:Making (S)VCDs under Linux

[ecloud]

I successfully made a couple SVCDs; but I started with digital video (from a digital 8mm camcorder) and played them on a DVD player (a Sampo model - they are probably the most versatile and hackable players). I didn't have any sync problems, but the video quality left a bit to be desired (it looks short of VHS quality to me, even though encoded at SVCD bitrate, and thus I can only get 1/2 hour on a disc). I did subtitles and of course they were the worst part to encode. I used MainActor for editing and subtitles; but video output from Kino is just as good, it's only that Kino is a bit under-featured at this point, so I got MA as a stopgap (and don't recommend it - it crashes a lot). SVCDs and VCDs can have chapters like DVDs, so it's best to put each chapter in its own AVI file (besides, AVI files have length limits - 2 gigs or something like that).

Here are my notes about how I made one disc:

edit-??.avi are exported from maseq using AVI-mjpeg, default quality, 720x480, 30fps, interlace A, de-interlaced

lav2yuv -A4:3 edit-01.avi | mpeg2enc -f4 -q6 -I0 -r32 -h -o wedding-ch1.m2v

lav2wav edit-01.avi | mp2enc -V -o wedding-ch1.mp2

mplex -f4 -V wedding-ch1.mp2 wedding-ch1.m2v -o wedding-ch1-svcd.mpg

...etc. for other AVI chapters, to produce interleaved MPEG files in the right format for SVCD; then...

vcdimager -tsvcd -c wedding.cue -b wedding.bin -l "Wedding" --volume-count=2 --volume-number=1 wedding-ch1-svcd.mpg wedding-ch2-svcd.mpg wedding-ch3-svcd.mpg wedding-ch4-svcd.mpg wedding-ch5-svcd.mpg

cdrdao write --driver generic-mmc-raw --device 1,1,0 wedding.cue

I wrote a script for this encoding project and went to bed; it took a long time.

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.