On Mon, 25 Apr 2005, Jean Carlos wrote:
> the reason why i'm converting to letter box its because i don't know if
> using mpeg2enc with -n n -F 4 -a 3 will give me a 16:9 dvd file with
After seeing the additional information you provided (thanks!) the
input file does not have the proper attributes to create a 16:9
DVD file from.
Initially I thought you had an anamorphic video or the producers
had created the file at 848x480.
> Yes u were right after checking the frame rate i realize that was in
> 23.97, by the way here's the output:
>
> VIDEO: [XVID] 640x360 24bpp 23.976 fps 945.9 kbps (115.5 kbyte/s)
Ah ha - I thought that was the case. So when you recoded with a
forced rate of "-F 4" the video would run about 25% fast.
> to reach the 30 fps seems to be i good idea to use a 3:2 pulldown,
> thanks a lot i never would realize how to change the fps without having
> the audio problem
You encode as 24000/1001 with the 2:3 pulldown. On a progressive
scan TV/DVD combination you have ~24 frames/sec each lasting 1/24'th
of a second (basically the repeated fields are ignored). When that
gets played on a non progressive setup the repeated fields are not
ignored/discarded and so you have ~30 frames/sec with each frame
lasting 1/30'th of a second. The end result in both cases is that
you have 1 second of video.
If that's too confusing then just think of it as "magic that works" :)
> > cat stream.yuv | head -n 1
> here's the other output:
> YUV4MPEG2 W640 H360 F23975999:1000000 Ip A0:0
>
> obviously this is the first line of the yuv header but i dont know what
> this means
It means 0) you have a YUV4MPEG2 stream, 1) The Width is 640 pixels,
2) the Height is 360 lines, 3) It was produced by MPlayer which
doesn't know to emit 24000:1001 instead of some weird floating point
number, 4) It's progressive (most AVI files are), and 5) It has an
unknown SAR (Sample Aspect Ratio of 0:0) - most naive video players
do that it turns out (in practice it means the pixels are 1:1 or
square).
What is needed is to place the 640x360 image in a 640x480 frame
with a black background. The resample/scale for 10:11 so we get a
704x480 DVD frame size.
I think something like this:
(decode the movie to YUV4MPEG2 as you were doing) | \
y4mscaler -I active=640x480+0+0cc -I sar=1:1 -O sar=10:11 -O size=704x480 -S
option=sinc:7 | \
mpeg2enc -f 8 -p -c -q 4 -E -10 -D 10 -4 1 -2 1 -o output.m2v
That will produce a full frame (704x480) letterboxed DVD compliant
MPEG-2 output file. In case you're curious where 704 comes from
the hint is in the "10:11" SAR and the fact that 640*11/10 is, well
you get the idea :)
> Probably i'm asking too much but if i would like to do a pal compilant,
> how i would do it from ntsc and telecine sources?
In general it's not possible to do a perfect job. To do that you'd
need to go from 24000/1001 to 25 frames/sec and then speed up the
audio by a similar amount. If there's a lot of music speeding up
the audio by ~4% drives some musicians nuts ;)
Getting the frame size correct for the video is trivial - just change
the 480 to 576. You will end up with window box bars in addition to
the letterbox ones - that can't be avoided with the dimensions of
the input video.
You can adjust the frame rate with 'yuvfps'. Dealing with the audio
and then getting A/V sync perfect is something you'll have to
experiment with :)
Cheers,
Steven Schultz
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