[ale] Digital VCR

Stuffed Crust pizza at shaftnet.org
Mon Sep 18 11:17:54 EDT 2000


On Mon, Sep 18, 2000 at 10:38:41AM -0400, Dow Hurst wrote:
> Can you guarantee that you can write 27Mb/s continuously for an hour? 
> What type drives and bus are you using?  You might need to tailor your
> machine some so other processes won't interfere.  Under IRIX you can
> assign a portion of the CPU to a task, can you do this under Linux? 
> Also, will 95Gbs raw compress down to a DVD in the current DVD format? 
> I don't know much about DVD except that you would need to get below 5Gb,
> right?

Behold, the beauty of RAID.  :)  Although I don't have a drive that can
push 27 megs/sec, when I stripe two or three drives that are capable of
about 15 megs/sec each, it'll handle it.  the 40meg/sec Fast-20 SCSI
bus will be fine.

The problem I have isn't the sustained transfer rate; it's the space
requirements.  I simply don't have 100G of storage, and even if I did, it
wouldn't be in drives large enough to not send the SCSI bus crazy.  
(after all, I have a limited budget -- otherwise this discussion would be
 moot.  :))

My plan is to crunch them to CDs, not DVDs.  :)  

On my Dual Celery 400, Running WinVCRII (under Win2K) I can do realtime
mpeg2 compression (sound/video) at 364x288 at 30fps (mpeg1 res) to a 4Mbps
stream.   I then crunch it down with mpeg4 ito a ~1Mbps stream, which runs
at about 0.25time.

1.8G/hr and ~400M/hr, respectively.  I'll probably tweak the mpeg4 stream
to max out a CD, but anyway.  The quality is about on-par with an average
VHS tape at that resolution, and I'm in the process of tweaking things to
find out just how high quality I can take things

My goal is to have a functioning system to do this recording by the 25th.  

Basically, under Windows the hardware support isn't there, but under
Linux, the software isn't up to par.

Broadcast2000a just can't cut it, unfortunately.  If I was going to do raw
recording, it would be the way to go, but its realtime compresison options
aren't that hot.  But even without that...

It's locked at 728x576 (max the bttv card can spitout) but at only 10fps!
Anyone here hav any experience with it?  I'm about to try and dig through
the source code to find out where that value is set.  I'd like to scale
the resolution down a bit but up it to 30fps.

 - Pizza
-- 
Solomon Peachy                                        pizza at cc.gatech.edu
I ain't broke, but I'm badly bent.                        +1(404)294-6978
Patience comes to those who wait.                            ICQ #1318344
    ...It's not "Beanbag Love", it's a "Transanimate Relationship"...
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