1
0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-12-07 11:13:41 +02:00
FFmpeg/libavcodec/mpeg4audio.h
Martin Storsjö d66c52c2b3 Add support for building shared libraries with MSVC
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>
2012-10-18 14:26:15 +03:00

110 lines
5.8 KiB
C

/*
* MPEG-4 Audio common header
* Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_MPEG4AUDIO_H
#define AVCODEC_MPEG4AUDIO_H
#include <stdint.h>
#include "get_bits.h"
#include "put_bits.h"
typedef struct MPEG4AudioConfig {
int object_type;
int sampling_index;
int sample_rate;
int chan_config;
int sbr; ///< -1 implicit, 1 presence
int ext_object_type;
int ext_sampling_index;
int ext_sample_rate;
int ext_chan_config;
int channels;
int ps; ///< -1 implicit, 1 presence
} MPEG4AudioConfig;
extern av_export const int avpriv_mpeg4audio_sample_rates[16];
extern const uint8_t ff_mpeg4audio_channels[8];
/**
* Parse MPEG-4 systems extradata to retrieve audio configuration.
* @param[in] c MPEG4AudioConfig structure to fill.
* @param[in] buf Extradata from container.
* @param[in] bit_size Extradata size in bits.
* @param[in] sync_extension look for a sync extension after config if true.
* @return On error -1 is returned, on success AudioSpecificConfig bit index in extradata.
*/
int avpriv_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf,
int bit_size, int sync_extension);
enum AudioObjectType {
AOT_NULL,
// Support? Name
AOT_AAC_MAIN, ///< Y Main
AOT_AAC_LC, ///< Y Low Complexity
AOT_AAC_SSR, ///< N (code in SoC repo) Scalable Sample Rate
AOT_AAC_LTP, ///< Y Long Term Prediction
AOT_SBR, ///< Y Spectral Band Replication
AOT_AAC_SCALABLE, ///< N Scalable
AOT_TWINVQ, ///< N Twin Vector Quantizer
AOT_CELP, ///< N Code Excited Linear Prediction
AOT_HVXC, ///< N Harmonic Vector eXcitation Coding
AOT_TTSI = 12, ///< N Text-To-Speech Interface
AOT_MAINSYNTH, ///< N Main Synthesis
AOT_WAVESYNTH, ///< N Wavetable Synthesis
AOT_MIDI, ///< N General MIDI
AOT_SAFX, ///< N Algorithmic Synthesis and Audio Effects
AOT_ER_AAC_LC, ///< N Error Resilient Low Complexity
AOT_ER_AAC_LTP = 19, ///< N Error Resilient Long Term Prediction
AOT_ER_AAC_SCALABLE, ///< N Error Resilient Scalable
AOT_ER_TWINVQ, ///< N Error Resilient Twin Vector Quantizer
AOT_ER_BSAC, ///< N Error Resilient Bit-Sliced Arithmetic Coding
AOT_ER_AAC_LD, ///< N Error Resilient Low Delay
AOT_ER_CELP, ///< N Error Resilient Code Excited Linear Prediction
AOT_ER_HVXC, ///< N Error Resilient Harmonic Vector eXcitation Coding
AOT_ER_HILN, ///< N Error Resilient Harmonic and Individual Lines plus Noise
AOT_ER_PARAM, ///< N Error Resilient Parametric
AOT_SSC, ///< N SinuSoidal Coding
AOT_PS, ///< N Parametric Stereo
AOT_SURROUND, ///< N MPEG Surround
AOT_ESCAPE, ///< Y Escape Value
AOT_L1, ///< Y Layer 1
AOT_L2, ///< Y Layer 2
AOT_L3, ///< Y Layer 3
AOT_DST, ///< N Direct Stream Transfer
AOT_ALS, ///< Y Audio LosslesS
AOT_SLS, ///< N Scalable LosslesS
AOT_SLS_NON_CORE, ///< N Scalable LosslesS (non core)
AOT_ER_AAC_ELD, ///< N Error Resilient Enhanced Low Delay
AOT_SMR_SIMPLE, ///< N Symbolic Music Representation Simple
AOT_SMR_MAIN, ///< N Symbolic Music Representation Main
AOT_USAC_NOSBR, ///< N Unified Speech and Audio Coding (no SBR)
AOT_SAOC, ///< N Spatial Audio Object Coding
AOT_LD_SURROUND, ///< N Low Delay MPEG Surround
AOT_USAC, ///< N Unified Speech and Audio Coding
};
#define MAX_PCE_SIZE 304 ///<Maximum size of a PCE including the 3-bit ID_PCE
///<marker and the comment
int avpriv_copy_pce_data(PutBitContext *pb, GetBitContext *gb);
#endif /* AVCODEC_MPEG4AUDIO_H */