[vorbis] Some comments about beta4

[Frank Heckenbach]

Hi,

I've just tried Ogg/Vorbis for the first time, and I'm quite
impressed with the results. I haven't heard any artifacts in my
tests so far, even at -b 112 (but I'm not a trained listener).
Thanks for the great work!

Now, some (mostly minor) points:

When building libvorbis on either a Linux/libc5 or a Solaris system,
both with gcc, it failed with undefined references to logf() etc.
I worked around by setting NO_FLOAT_MATH_LIB in lib/os.h
unconditionally. Of course, it would be better if the library would
detect this automatically. How about an autoconf check for logf()?

When building the libs on a foreign system without installing them
in the system directories, I tried to configure libvorbis
--with-ogg-prefix, but this didn't quite work. The Ogg test program
compiled and linked, but didn't run because LD_LIBRARY_PATH wasn't
set. To solve the problem for now, I inserted

LD_LIBRARY_PATH="$ogg_prefix/lib:$LD_LIBRARY_PATH"; export LD_LIBRARY_PATH

in configure (after OGG_LIBS="-L$ogg_prefix/lib" libvorbis). -- I
know that it should actually be changed in aclocal.m4, but I didn't
have (a current version of) autoconf on that system, so I didn't try
this. (The same issue occurred in vorbis-tools for libao, libogg and
libvorbis.)

oggenc(1) says:

:        -b n, --bitrate=n
:               Sets  encoding  to  the  bitrate  closest  to n (in
:               kb/s). Defaults to 160 kb/s for stereo.

In fact, the default seems to be 128.

ogg123(1) says:

:        -v, --verbose
:               Increase verbosity.  (Currently not implemented.)

Well, apparently it is implemented. :-)

The bit rate that is displayed with `-v', is this the rate of the
current frame or the average of all frames played so far? If it's
the former, it would be nice to also see the latter.

When encoding a WAV file with broken header (wrong size
information), oggenc used the wrong size to compute the percentage
and remaining time, so they were quite wrong. Of course, that's not
a bug, but since broken WAV files are not uncommon, it might be a
good idea to base the calculation also on the file size. (It's not
really important to me, just thought I'd mention it...)

ogg123(1) says:

:        solaris
:               Solaris audio driver.  Note that  this  driver  has
:               not been tested!

So, I just wanted to test it... but I couldn't find it. It doesn't
seem to be contained in libao-0.6.0.tar.gz. Where can I get that
code?

Finally a question about encoding speed. Segher mentioned a 3-4x
speedup recently. Is this incorporated in beta4 already, or can I
look forward to it? (Beta4 is the first version I've used, so I
can't compare.) Currently, oggenc is doing slightly more than 50% on
my "ancient" home system (K6/233). Can I hope for realtime encoding
on this machine in the future, or is this not realistic?

Frank


-- 
Frank Heckenbach, frank at g-n-u.de
http://fjf.gnu.de/
PGP and GPG keys: http://fjf.gnu.de/plan

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