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Linshizhi
ffmpeg.wasm-core
Commits
cacf7199
Commit
cacf7199
authored
Oct 01, 2004
by
Mike Melanson
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FAQ update; entry on C++
Originally committed as revision 3542 to
svn://svn.ffmpeg.org/ffmpeg/trunk
parent
669484b4
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faq.texi
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doc/faq.texi
View file @
cacf7199
...
...
@@ -10,22 +10,22 @@
@chapter General Problems
@section ffserver does
n't
not work.
@section ffserver does not work.
ffmpeg development is now concentrated on the codec and format
handling. New developments broke ffserver, so don't expect it to work
correctly. If you have time and experience, please help us fix it.
@section I cannot read this file although this format seems to be suppored by ffmpeg.
@section I cannot read this file although this format seems to be suppor
t
ed by ffmpeg.
Even if ffmpeg can read the file format, it may not support all its
codecs. Please consult the supported codec list in the ffmpeg
documentation.
@section I get audio/video synchro problems when grabbing.
@section I get audio/video synchro
nization
problems when grabbing.
Currently, the grabbing stuff does not handle synchronisation
correctly. You are free to correct it.
It is planned to fix it ASAP
.
correctly. You are free to correct it.
A fix is planned
.
@section How do I encode jpegs to another format ?
...
...
@@ -49,17 +49,19 @@ portable, bloated and often slow.
@section Why do I see a slight quality degradation with multithreaded MPEG* encoding ?
For multithreaded MPEG* encoding, the encoded slices must be independent,
otherwise thread n would practically have to wait for n-1 to finish, so its
quite logic
that there is a small reduction of quality, this is not a bug
otherwise thread n would practically have to wait for n-1 to finish, so it
'
s
quite logic
al that there is a small reduction of quality. This is not a bug.
@section How can I read from the standard input or write to the standard output ?
Use @file
{
-
}
as filename.
@section Why
Audio is not decoded
in VOB files ?
@section Why
does ffmpeg not decode audio
in VOB files ?
AC3 decoding is optional as the codec is currently released under the
GPL. Enable it with @code
{
./configure --enable-a52
}
. Take care: by
The audio is AC3 (a.k.a. A/52). AC3 decoding is an optional component in ffmpeg
as the component that handles AC3 decoding (liba52) is currently released under
the GPL. If you have liba52 installed on your system, enable AC3 decoding
with @code
{
./configure --enable-a52
}
. Take care: by
enabling AC3, you automatically change the license of libavcodec from
LGPL to GPL.
...
...
@@ -83,10 +85,10 @@ only if you have some mpeg4 codec installed like ffdshow or xvid
@item mpeg1
.mpg only
@end table
note, asf often uses .wmv or .wma extensions in windows, it should also be
mentioned that asf is patented, so microsoft may sue or threaten users who
use it if they see any reason to do so, it is strongly recommanded to avoid asf
for any use
Note, asf files often have .wmv or .wma extensions in windows. It should also
be mentioned that Microsoft claims a patent on the ASF format, and may sue
or threaten users who create ASF files with non-Microsoft software. It is
strongly advised to avoid ASF where possible.
The following list of audio codecs should work on most windows systems
@table @option
...
...
@@ -97,49 +99,51 @@ The following list of audio codecs should work on most windows systems
if some mp3 codec like lame is installed
@end table
@section
The chrominance seems to come from a different time then the luminance on bt8x8 captures on l
inux?
@section
Why does the chrominance data seem to be sampled at a different time than the luminance data on bt8x8 captures on L
inux?
well known bug in the bt8x8 driver, for 2.4.26 there
s a patch at
(@url
{
http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch
}
)
, i suspect that
this will also apply cleanly to other 2.4 kernels
This is a well-known bug in the bt8x8 driver. For 2.4.26 there i
s a patch at
(@url
{
http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch
}
)
. This may also
apply cleanly to other 2.4-series kernels.
@section How
to avoid the ugly aliassing arte
facts in bt8x8 captures on linux?
@section How
do I avoid the ugly aliassing arti
facts in bt8x8 captures on linux?
pass 'combfilter=1 lumafilter=1' to the bttv driver, n
ote though that 'combfilter=1'
will cause somewhat too strong filtering
, a fix is to
o apply (@url
{
http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch
}
)
Pass 'combfilter=1 lumafilter=1' to the bttv driver. N
ote though that 'combfilter=1'
will cause somewhat too strong filtering
. A fix is t
o apply (@url
{
http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch
}
)
or (@url
{
http://www.mplayerhq.hu/~michael/bttv-comb-2.6.6.patch
}
)
and pass 'combfilter=2'
and pass 'combfilter=2'
.
@section I have a problem with an old version of ffmpeg
,
where should i report it?
Nowhere
, u
pgrade to the latest release or if there is no recent release upgrade
to cvs
, you could also try to report it, maybe you are
lucky and
will become the first person in history to get a different awns
er from "upgrade
@section I have a problem with an old version of ffmpeg
;
where should i report it?
Nowhere
. U
pgrade to the latest release or if there is no recent release upgrade
to cvs
. You could also try to report it. Maybe you will get
lucky and
become the first person in history to get a different answ
er from "upgrade
to cvs".
@section -f jpeg doesnt work.
try '-f image -img jpeg test
%d.jpg'
@section
i cant change the framerate
@section
Why can I not change the framerate?
some codecs, like mpeg1/2 only allow a small number of fixed framerates,
choose a different codec with -vcodec
Some codecs, like MPEG 1/2 only allow a small number of fixed framerates.
Choose a different codec with the -vcodec command line option.
@section
it doesnt work
@section
ffmpeg does not work; What is wrong?
try a 'make distclean' if this doesn
t help see
(@url
{
ffmpeg-bugreport.html
}
)
Try a 'make distclean' in the ffmpeg source directory. If this does no
t help see
(@url
{
ffmpeg-bugreport.html
}
)
.
@chapter Development
@section Are there examples
of use of the FFmpeg libraries
libavcodec and libavformat ?
@section Are there examples
illustrating how to use the FFmpeg libraries, particularly
libavcodec and libavformat ?
Yes. Read the Developers Guide of the FFmpeg documentation.
Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively,
examine the source code for one of the many open source projects that
already incorporate ffmpeg at (@url
{
projects.php
}
).
@section Can you support my C compiler XXX ?
No. Only GCC is supported. GCC is ported
on most systems available and I
don't see the
need to pollute the source code with @code
{
#ifdef
}
s
No. Only GCC is supported. GCC is ported
to most systems available and there
is no
need to pollute the source code with @code
{
#ifdef
}
s
related to the compiler.
@section Can I use FFmpeg or libavcodec under Windows ?
...
...
@@ -147,16 +151,25 @@ related to the compiler.
Yes, but the MinGW tools @emph
{
must
}
be used to compile FFmpeg. You
can link the resulting DLLs with any other Windows program. Read the
@emph
{
Native Windows Compilation
}
section in the FFmpeg documentation
to
have
more information.
to
find
more information.
@section Can you add automake, libtool or autoconf support ?
No. These tools are too blo
w
ted and they complicate the build. Moreover,
No. These tools are too blo
a
ted and they complicate the build. Moreover,
since only @samp
{
gcc
}
is supported they would add little advantages in
terms of portability.
@section
ffmpeg doesnt contain any debugging symbols
?
@section
Why not rewrite ffmpeg in object-oriented C++
?
try ffmpeg
_
g, ffplay
_
g, ...
ffmpeg is already organized in a highly modular manner does not need to
be rewritten in a formal object language. Further, many of the developers
favor straight C; it works for them. For more arguments on this matter,
read "Programming Religion" at (@url
{
http://lkml.org/faq/lkmlfaq-15.html
}
).
@section Why are the ffmpeg programs devoid of debugging symbols ?
The build process creates ffmpeg
_
g, ffplay
_
g, etc. which contain full debug
information. Those binaries are strip'd to create ffmpeg, ffplay, etc. If
you need the debug information, used the *
_
g versions.
@bye
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