Re: debconf5 - videos of the talks and BOFs available
On Mon, 2005-07-25 at 11:25 +0100, Ben Hutchings wrote:
> Herman Robak wrote:
>
> > Does this process involve recoding, or can vanilla DVD players
> > handle the non-constrained MPEG1 streams that we have published?
>
> I originally hoped to be able to use the MPEG1 streams unaltered, so
> that the DVD could be distributed as a jigdo, but I have now resorted
> to using mencoder to recode into MPEG2 and scale to full size at the
> same time.
Recoding back to a higher resolution is a no-no, when avoidable.
> > We still have most of the raw material, and John has the rest in
> > high quality full resolution XviD. Recoding from that would yield
> > more pleasant results.
>
> Yes - though they would also be much larger. I'm getting everything
> onto two single-layer or one dual-layer disc by recoding to roughly
> the same bit rate as the source files from dc5video.
You could encode from the original sources with the same bitrate,
but that would probably result in a lot of ugly artifacts. 400 kbit/s
is not a reasonable bitrate for 720x576 video using MPEG2. If I recall
correctly, DVD players can handle 352x288, too. I don't remember what
the exact constraints were on the audio. I suspect 32 KHz is out of
spec, and that 44.1 KHz is required.
> > And a 48 frames GOP is way beyond the 12-15 of VCD and DVD.
>
> Assuming that the GOP length is the same as what mencoder calls
> "keyframe interval", it claims the maximum is 132,
I think the maximum for unconstrained MPEG is even higher,
but you can't expect that to work on a standalone DVD player!
> so that's what I selected when recording. Which would explain
> why seeking doesn't work very well on my test discs... So I'll
> fix that.
If you want to be sure that the video is playable on all DVD
players, the GOP should not be larger than 12 for PAL and 15 for
NTSC. This is less efficient for low-motion content like these
conference recordings. However, it is prudent to make sure that
the DVD plays without a hitch even on the most inept players.
--
Herman Robak
--
To unsubscribe, send mail to debconf5-event-unsubscribe@lists.debconf.org.
Reply to: