[MPlayer-users] Mencoder: Changing frame rate (RealMedia to vcd)
comes at naic.edu
Sun Jan 2 00:12:56 CET 2005
On Sat, Jan 01, 2005 at 12:23:44PM -0800, Bill Moseley wrote:
> On Sat, Jan 01, 2005 at 03:35:09PM -0400, Giacomo Comes wrote:
> > In general going from resolution A aspect B to resolution C aspect D
> > requires expand and scale or scale and expand.
> Why does it make a difference (other than a bug in some software)?
The only difference is in the numbers.
Example: video 576x288 aspect 2:1 to convert to 16/9 720x480 (NTSC DVD)
with expand and scale you need:
-vf expand 576:324,scale=720:480
with scale and expand you need:
The final result is exactly the same (other than bug).
> My basic understanding is you can pick 16:9 or 4:3 so you have to
> expand, that is, convert the current image to one of those ratios by
> either adding black bars (to keep all the image) or by
> trimming/cropping. Then it needs to be resized to fit the target
> format (i.e. 720x480 for dvd). And then there has to be a flag to
> tell the player if it's 16:9 or 4:3.
> [What happens after to get the image is shown on my direct view
> 16:9 TV is a mystery to me.]
> > By the way encode2mpeg deals with all these situations. The option
> > -mpegfixaspect is your friend.
> Yes, very cool. I've been playing with this sample:
> And using this command line:
> encode2mpeg -o STEST -n p -mpegfixaspect pad -imageonly -mpeg -svcd sample.rm
> I get a lot of "[mpeg2video @ 0x403b9008]rc buffer underflow" and
> other messages. I'm not sure if that indicates a problem or not.
Most of the time no. The current
mpeg muxer in mencoder produce them and it's not possible to avoid them.
> And I have not figured out how to make the resulting mpeg flagged as
> 16:9 content. I've tried this:
> encode2mpeg -o STEST16 -a 3 -n p -mpegfixaspect pad -imageonly -svcd -mpeg sample.rm
the command is correct. -a 3 set 16/9 aspect.
> BTW -- you recommended
> encode2mpeg -o MYREAL -n n input.rm -encode 2
> doesn't that make a divx intermediate file? It's that a lossy
> operation to go from Real -> divx-> mpeg1/2?
Yes it's lossy, but I'm sure you will not notice any difference.
-encode 2 keep the quality good in the avi. But in case there is
a visible loss in the quality you can use -encode 4.
I recomended the previous line (Indirect Mode) because I'm still
trimmering the libavcodec options of Mpeg Mode.
I'm almost done and in next relase Mpeg Mode will be "well defined".
> Thanks very much -- the encode2mpeg is a huge help.
More information about the MPlayer-users