[MPlayer-users] Re: Help w/ Mencoder anyone? DVD->DivX + TVcapture->DivX + vop scale probs

[Diego Zuccato]

Rémi Guyomarch wrote:

> Let's say that you're capturing 25 fps at 320x240.
> Each frame will probably be packed in YV12, which means 153600 bytes
> per frame or 3.66 MBytes per second or ~13 GBytes per hour.
Maybe from an old VHS tape :-)
> Multiply those numbers by 4 if you want to capture at 640x480 instead
> of 320x200.
That's more reasonable for newer S-video tapes. :-) I'd still prefer
720x576, just to have the full frame :-)
So that should bring about 20MB/s, right?
Plus the audio track. Say 24MB/s just to be sure and account for some
random disk glitches.

> Any half-decent modern IDE hard drive can easily sustain 4 MBytes/s
> but 15-16, that's another story ...
The disk in my laptop (a 2.5" 10GB IBM drive, for sure not one of the
best!) could write at 8MB/s without problems, when I tried it.
Any decent 3.5" 7200RPM IDE drive could do better.

> I don't know much about lossless video recording, but I bet such codec
> won't be able to scrap more than 50% of that bandwidth ...
Could be enough. So it's 12MB/s. Using a good controller (like Adaptec
2400) and 4 half-decent 80GB disks in striping mode the bw per-disk is
only 3MB/s and there's room for more than 3 hours. Without lossless
compression it's 1.5h and 6MB/s per disk = bigger & better disks.
Such a beast could then be encoded to anything (from near-DVD-quality to
aa-lib) having the best possible quality for the target. Using a lossy
compressor instead would penalyze the top quality 2nd encoding...

BYtE,
 Diego.