It is small (16 B) and therefore the overhead of exporting it more
than outweighs the size savings from not having duplicated symbols:
When the symbol is no longer avpriv, one saves twice the size of
the string containing the symbols name (2x30 byte), two entries
in .dynsym (24 bytes each on x64), one entry in the importing libraries
.got and .rela.dyn (8 + 24 bytes on x64) and two entries for the
symbol version (2 bytes each) and one hash value in the exporting
library (4 bytes).
(The exact numbers are of course different for other platforms
(e.g. when using dlls), but given that the strings saved alone
more than outweigh the array size it can be presumed that this
is beneficial for all platforms.)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Added in 0c79b1402a to use it
in a function that was never used and was itself removed in
676f1f533e.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This is required to use it as an AVCodec.supported_samplerates array.
Adding the sentinel has been forgotten in 4679a474.
Without it e.g. the FATE-test ffmpeg-filter_complex_audio fails with ASAN.
Reviewed-by: Carl Eugen Hoyos <ceffmpeg@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
We currently only have exported data symbols within libavcodec, but
the concept is easy to extend to other libraries if necessary.
The attribute declaration needs to be in a private header though,
since we can't use CONFIG_SHARED in public installed headers.
Signed-off-by: Martin Storsjö <martin@martin.st>
The table in question is a 253 byte one. In fact, it turns out that
dynamic generation of the table results in an increased binary size.
Code compiled with GCC 5.2.0, x86-64 (size in bytes), before and after
patch:
old: 62321064 libavcodec/libavcodec.so.57
new: 62320536 libavcodec/libavcodec.so.57
Thus, it always make sense to statically allocate this.
Tested with FATE with/without --enable-hardcoded-tables.
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
This requires the makedef perl script by Derek, from the
c89-to-c99 repo. That scripts produces a .def file, listing
the symbols to be exported, based on the gcc version scripts
and the built object files.
To properly load non-function symbols from DLL files, the
data symbol declarations need to have the attribute
__declspec(dllimport) when building the calling code. (On mingw,
the linker can fix this up automatically, which is why it has not
been an issue so far. If this attribute is omitted, linking
actually succeeds, but reads from the table will not produce the
desired results at runtime.)
MSVC seems to manage to link DLLs (and run properly) even if
this attribute is present while building the library itself
(which normally isn't recommended) - other object files in the
same library manage to link to the symbol (with a small warning
at link time, like "warning LNK4049: locally defined symbol
_avpriv_mpa_bitrate_tab imported" - it doesn't seem to be possible
to squelch this warning), and the definition of the tables
themselves produce a warning that can be squelched ("warning C4273:
'avpriv_mpa_bitrate_tab' : inconsistent dll linkage, see previous
definition of 'avpriv_mpa_bitrate_tab').
In this setup, mingw isn't able to link object files that refer to
data symbols with __declspec(dllimport) without those symbols
actually being linked via a DLL (linking avcodec.dll ends up with
errors like "undefined reference to `__imp__avpriv_mpa_freq_tab'").
The dllimport declspec isn't needed at all in mingw, so we simply
choose not to declare it for other compilers than MSVC that requires
it. (If ICL support later requires it, the condition can be extended
later to include both of them.)
This also implies that code that is built to link to a certain
library as a DLL can't link to the same library as a static library.
Therefore, we only allow building either static or shared but not
both at the same time. (That is, static libraries as such can be,
and actually are, built - this is used for linking the test tools to
internal symbols in the libraries - but e.g. libavformat built to
link to libavcodec as a DLL cannot link statically to libavcodec.)
Also, linking to DLLs is slightly different from linking to shared
libraries on other platforms. DLLs use a thing called import
libraries, which is basically a stub library allowing the linker
to know which symbols exist in the DLL and what name the DLL will
have at runtime.
In mingw/gcc, the import library is usually named libfoo.dll.a,
which goes next to a static library named libfoo.a. This allows
gcc to pick the dynamic one, if available, from the normal -lfoo
switches, just as it does for libfoo.a vs libfoo.so on Unix. On
MSVC however, you need to literally specify the name of the import
library instead of the static library.
Signed-off-by: Martin Storsjö <martin@martin.st>
Channel coupling is an optional AC-3 feature that increases quality by
combining high frequency information from multiple channels into a
single channel. The per-channel high frequency information is sent with
less accuracy in both the frequency and time domains. This allows more
bits to be used for lower frequencies while preserving enough
information to reconstruct the high frequencies.
This improves the audio quality significantly for stereo source with both the
fixed-point and floating-point AC-3 encoders.
Update acodec-ac3_fixed and seek-ac3_rm test references.
Originally committed as revision 26271 to svn://svn.ffmpeg.org/ffmpeg/trunk
Consistently apply this rule: the guard name is obtained from the
filename by stripping the leading "lib", converting '/' and '.' to
'_' and uppercasing the resulting name. Guard names in the root
directory have to be prefixed by "FFMPEG_".
Originally committed as revision 15120 to svn://svn.ffmpeg.org/ffmpeg/trunk
Andreas Rheinhardt
Andreas Rheinhardt
Lynne
Carl Eugen Hoyos
Michael Niedermayer
Martin Storsjö
Ganesh Ajjanagadde
Diego Biurrun
Justin Ruggles
Mans Rullgard
Stefano Sabatini
Bartlomiej Wolowiec
Aurelien Jacobs
Benjamin Larsson
Michael Niedermayer
Alex Beregszaszi
Zdenek Kabelac
Fabrice Bellard