[MEncoder-users] capture: synchronization problems

[Oded Shimon]

On Wed, Mar 23, 2005 at 11:28:22AM +0100, amber wrote:
> > Plus, if you are going to re-encode to MPEG2/4 later, it's better to stick with a
> > codec in the same family.

IMO, I really don't agree with this. You should capture using some kind of 
high quality (or even lossless) codec, and then re-encode properly to whatever 
target codec you intend.

> i'm not very much familiar with those codecs and capturing - still a newbie. could
> somebody please summarize it?
> 
> i understand mjpeg causes some artifacts.

I've never seen such artifacts. I could be wrong though. Could someone tell me 
exactly what artifacts? MJPEG by definiton is lossy, but for all my capturing 
needs I found it very high quaality at small filesize.

> mpeg2 and 4 do not. and they are almost as fast
> or even faster so they sould be used instead mjpeg, provided the keint is set to 1.
> there will be no problems with further editing. is that right?

If you set keyint to 1, just about the only gain made by using these codecs is 
lost. The only reason I know of using MPEG4/2 for capturing is for HD space, 
they are much smaller. If you use keyint=1, you end up with almost exactly 
same filesize.

> now, mpeg4 is in fact divx/xvid - is that right? and mpeg2 is DVD?

MPEG-4 is a standard. DIVX and XVID are specific implementations of that 
standard. MPEG-2, when put in a specific container, is DVD.

> so if the target format of the recorded material is going to be dvd, i should use
> mpeg2 and if i want to watch it on a PC, i should use mpeg4 (especially that more and
> more dvd players can play divx). can somebody verify it?

IMHO, if you have a lot of HD space, capture with ffvhuff, it's a lossless 
codec and about as small as they come. As for lossy high quality codecs, MJPEG 
is the best there is. CPU is hardly an issue, unless you have a 300mhz or so. 
My 500mhz box captured with MJPEG at 80% cpu without dropping a single frame. 
I don't think you'll get any faster/better results with other codecs.
If you're really tight on hd space, you can use mpeg4, with vme=1 and 
keyint=250 . This will make editing slightly a pain.

Only after capturing with these codecs should you use MPEG-2 and MPEG-4 for 
encoding. When capturing you just grab as much data as possible, never caring 
about the end result.

These are all just my opinions. Feel free to flame me, but only if you have 
proof behind your flames.

- ods15