On Thu, 16 Nov 2006, Kim Richardson wrote:
Hi!
> 1) The size of the input images that work are 240x160, but we would
> like to make these bigger, and short of going through the code I have
> not been able to find a way to do this. Now I uderstand that the mpeg-1
> standard is 352x240, which also is small for our desired application.
> Have I missed something that would allow us to make bigger imagery into
> an avi file?
Yes :)
You missed the part in the MPEG specs that allow up to 4096x4096 <g>
There is a common misconception that MPEG-1 is limited to the CIF frame
size (also known as the 'VCD' size) of 352x240 (or 352x288 for 625
line video systems). That is a subset of MPEG-1 with the
'constrained parameters' flag set.
MPEG-1 itself can go way up - I've heard mention of 4K being legal
(but the encoding times would be horrific I'd think ;)).
But MPEG sets limits on the frame rate - you can see the list of
valid rates by using "mpeg2enc -F 0"
mpeg2enc -F 0
Frame-rate codes:
0 - UNDEFINED: illegal/reserved frame-rate ratio code
1 - 24000.0/1001.0 (NTSC 3:2 pulldown converted FILM)
2 - 24.0 (NATIVE FILM)
3 - 25.0 (PAL/SECAM VIDEO / converted FILM)
4 - 30000.0/1001.0 (NTSC VIDEO)
5 - 30.0
6 - 50.0 (PAL FIELD RATE)
7 - 60000.0/1001.0 (NTSC FIELD RATE)
8 - 60.0
> 2) When using the command: system("$jpeg2yuv -f $frames_per_second -I
> p -j file_%02d.jpg | $yuv2lav -f a -q 80 -o $avi_filename");
> I would like to set the frames per second to be much slower than the
> default, but when the avi file is played by IE, it looks like 24 fps or
> there abouts. For science it is much better to have the fps around 10
> or less, this way you can actually see the dynamical change in the weather.
I am not sure if it is necessary to specify the frame rate as a
colon sep list ("-f 15:1" instead of "-f 15") or not.
You may need to use 'yuvfps' to do a rate change (time lapse or slow
motion) though since MPEG-1/2 limits the frame rates to the ones
listed above.
Cheers,
Steven Schultz
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