Reporting VLC usage on RedHat-7.1

[David Madore]

Hi all.

I'd like to report that I've compiled and used VLC successfully on
RedHat-7.1 - to read DVD's.  Here are a few comments I wish to make:

First, I should say that your project is considerably better than the
competition.  The display of subtitles and the ability to select
chapters in DVD's, are irritatingly lacking in xmovie; also, VLC's
display seems smoother than xmovie's, and the CSS cracking code works
*much* better.  As for the OMS project from video4linux, it is still
bare bones.

However, VLC does have one big problem: it segfaults all too often.

I could send you a dozen crash reports, but I won't do so just now
because I first want to know whether they're of any value - basically,
they are so easy to reproduce that they can hardly be unkown.

Some segfaults could very well turn out not to be your fault at all.
It is "well known" that the combination of the libpthread that comes
with glibc-2.2.[0-3] and the Linux kernel 2.4.[0-6] (at least) causes
tremendous difficulties, and just about any threaded program can
segfault, especially on SMP machines, anywhere in the pthread_*()
functions (from pthread_create() all the way to pthread_join()).  See
<URL: http://sources.redhat.com/ml/bug-glibc/2001-07/msg00076.html >
for more details.  That Gnome inserts its own segfault handler does
not help to diagnose problems: for example, preloading the
libSegFault.so does not permit the printing of a backtrace.

Similar to segfaults, I have observed many cases where the video would
just stop playing (while the sound went on unperturbed).  I assume
this is a case of one thread freezing up or dying mysteriously
(another thing which could be either due to the libpthread bugs or to
the program itself).  Basically, whenever I try to seek to a specific
location on the DVD by moving the position cursor, I have problems
like this.  Once the video freezes (the same image stays on display),
it never seems to start again, whatever I try.

Another thing: the new CVS snapshots have a --smp option for VLC.  I
tried to use it (I have a two-way SMP machine), but it basically makes
things much worse (as in, displaying one image every five seconds
instead of making things more fluid).

Finally, the fact that the yuvmmx display plugin will not work when
compiled with gcc>2.95 is most annoying.  And it is certainly not
RedHat's fault since I have tried it also with the official gcc-3.0
release, to the same effect.  Looking at transforms_yuvmmx.c I see the
following lines:

            __asm__( MMX_INIT_16_GRAY
                     : : "r" (p_y), "r" (p_u), "r" (p_v), "r" (p_buffer) );
            __asm__( ".align 8"
                     MMX_YUV_GRAY
                     MMX_UNPACK_16_GRAY
                     : : "r" (p_y), "r" (p_u), "r" (p_v), "r" (p_buffer) );

i.e. asm statements with no output operands and no "volatile" keyword.
Well the compiler would be quite in its rights to simply optimize them
away, wouldn't it?  After all, they are officially supposed to do
nothing at all.  Surely there's something wrong, here.

I hope this information is of some use.

Cheers,

-- 
     David A. Madore
    (david.madore at ens.fr,
     http://www.eleves.ens.fr:8080/home/madore/ )

(Notes: I am not subscribed to the mailing-list.  Of course I
understand French if that is more agreeable.)