On Wed, 8 Oct 2003, Maarten de Boer wrote:
> and I have to do it at home, where I can dedicate only limited time to
> it), but indeed -K kvcd improved a lot. I left out the -N option because
> I don't think my source material is that noisy, and I am not sure if it
-N is not primarily aimed at denoising (that is yuvdenoise's job ;))
Usually a good idea to add "-N value" with "-K kvcd" anyhow since the
quantization matrices for kvcd already contain modifications to
the high frequency quantizers.
> is really necesary to use the -l 1 for yuvdenoise. I have not tried to
> the new SVCD on my DVD player yet, so I can not say if it looks better
> than the VCD, but my impression (from watching with mplayer) is that it
> isn't...
Enlarge the image ;) VCDs are 352x240 or just slightly bigger
than a thumbnail image - when played back at a 4:3 aspect it gets
scaled to 352x264 (by MPlayer at least). SVCDs are encoded at
480x480 (NTSC) with a 4:3 aspect meaning they play back at 640x480 or
almost twice the size of a VCD playback image. Basically you're
getting a much larger image at the same or (for me) better quality.
> I notice some strange artefacts, that I noticed also in the VCD, when playing
> with mplayer, but not when playing on the DVD+TV): blue "lightning": small
Hmmm, can't say I've seen that effect. I see a "blue streaks" effect
when using ffmpeg on a G4 system running OS/X but I think that's
a different issue.
> Another question: Dan Dennedy mailed a script to the kino-dev mailing
> list to convert dvgrab output to mpeg2 (for DVD) using ffmpeg. Now, this
> might be a good moment to ask something I have on my mind for quite a
> while. What would be the main advantages/disadvantages between ffmpeg,
> mjpegtools (and mencoder)? (for this particular purpose, converting DV
> to mpeg2 for DVD/SVCD/VCD) ?
I have not tried it but I have my doubts that ffmpeg, as fast as
it is, can do DVD sized MPEG-2 encoding in real time.
What happens if the encoding can't keep up? Does it drop frames? I
don't believe it's possible to stop/start a VHS tape deck accurately
enough to implement flow control that way.
Also, did you notice that his system was a dual cpu system? That
gives it a big advantage over most systems since the DV decoding
(and audio encoding) can be done in parallel with the video
encoding and in fact he mentioned using two ffmpeg processes to
take advantage of the SMP capability. With mpeg2enc the -M 2
will use an additional cpu for the encoding.
The main disadvantages I see with a all in one capture/encode method
are 1) lack of editing - can't trim off the leading/trailing junk
or commercials/trailers/advertisements/etc, 2) no flow control - what
happens if the encoding can't, even momentarily, keep up (disc accesses,
other programs running, whatever), 3) relative maturity - the VCD/SVCD
creation with ffmpeg has worked for some and not for others. At the
time the issue was the bitrate control - big spikes in the bitrate
will be tolerated by software players but not hardware ones (for DVDs
the bitrate range is larger of course and easier to not exceed).
4) what if you want to try multiple encodings with different
parameters? Run the tape again I suppose ;)
I'll have to try ffmpeg's MPEG-2 encoding and see how fast it
actually is but realtime 720x480 or 720x576 I am doubtful (realtime
VCD MPEG-1 I have seen work on a fast system).
Cheers,
Steven Schultz
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