[mpeg2-dev] MPEG Distortion and general Libmpeg2 questions

[Alvin B. <ab...@de...>]

Hello,

=46irst I would like to thank Eric and M=E5ns for their quick response to m=
y=20
previous linking error. I can now use the libmpeg2 library. However, I have=
=20
come across some things that perhaps someone can help me with.

1. I have written a very simple application that takes x number of frames f=
rom=20
a MPEG2 file and write them as PGM files. This is almost the same as=20
sample1.c in the doc directory. However, the PGM files that are produced=20
appear to be mangalled. I think the term is "MPEG Distortion"? The image ha=
s=20
blocks spread throughout? I have tried with both my program and with=20
sample1.c and the PGM file produced are both distorted? The MPEG2 file I am=
=20
experimenting with is a recording of a TV show encoded by a PVR-250.

2. In sample1.c it appears too much data is being written in save_pgm(). In=
 my=20
mpeg2pgm test program, I just write info->display_fbuf->buf[0] as the PGM=20
data portion and the resulting PGM file looks to be correct? If there a=20
reason why sample1.c's save_pgm() writes fbuf[0] and then interlaces fbuf[1=
]=20
and fbuf[2] (with half the width and height)??

3. I am using the mpeg2dec-snapshot.tar.gz as of September 4, 2003. Accordi=
ng=20
to the txt file in doc, it says that info->display_fbuf->buf is the YUV=20
encoded pixels of the picture. However, I have experimented with writing=20
info->display_fbuf->buf[0] to a PGM file and by converting 'buf' to RGB24=20
using 'convert_rgb24' as in sample2.c (writing PPM) and just writing the=20
GREEN plane. The two resulting PGM files appear to be identicle?

3. My test MPEG2 file (which came from a PVR-250) run perfectly with MPlaye=
r=20
but my test program appears to only get distorted frame data? Since MPlayer=
=20
uses the libmpeg2 library, is there some special library initialising that=
=20
needs to be done that is not done in the sample applications in the doc=20
directory?

Thank you for any help or clarification that you can give me.

=2D-=20
Alvin Beach

Email: abeach_at_deepvision_dot_ca