ffmpeg 源代码简单分析 ： avcodec_register_all()

此前写了好几篇ffmpeg源代码分析文章，列表如下：

图解FFMPEG打开媒体的函数avformat_open_input

ffmpeg
源代码简单分析 ： av_register_all()

ffmpeg
源代码简单分析 ： avcodec_register_all()

ffmpeg
源代码简单分析 ： av_read_frame()

ffmpeg 源代码简单分析 ： avcodec_decode_video2()

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本文分析一下ffmpeg注册编解码器等的函数avcodec_register_all()（注意不是av_register_all()，那是注册所有东西的）。该函数在所有基于ffmpeg的应用程序中几乎都是第一个被调用的。只有调用了该函数，才能使用编解码器等。

之前已经写过一篇文章了：

ffmpeg 源代码简单分析 ： av_register_all()

其实注册编解码器和注册复用器解复用器道理是差不多的，重复的内容不再多说。

编码器的注册是：

REGISTER_ENCODER (X,x);

例如：

REGISTER_ENCODER (LJPEG, ljpeg);

解码器的注册是：

REGISTER_DECODER (X,x);

例如：

REGISTER_DECODER (H264, h264);

既包含编码器有包含解码器的注册是：

REGISTER_ENCDEC (X,x);

例如：

REGISTER_ENCDEC (BMP, bmp);

此外还有几种注册：

Parser：

REGISTER_PARSER (X,x);

例如：

REGISTER_PARSER (H264, h264);

BSF（bitstream filters，比特流滤镜，有一个常用：h264_mp4toannexb）：

REGISTER_BSF (X,x);

例如：

REGISTER_BSF (H264_MP4TOANNEXB, h264_mp4toannexb);

HWACCEL（hardware accelerators，硬件加速器）：

REGISTER_HWACCEL (X,x);

例如：

REGISTER_HWACCEL (H264_DXVA2, h264_dxva2);

我们来看一下宏的定义，这里以编解码器为例：

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#define REGISTER_ENCODER(X,x) { \

extern AVCodec ff_##x##_encoder; \

if(CONFIG_##X##_ENCODER) avcodec_register(&ff_##x##_encoder); }

#define REGISTER_DECODER(X,x) { \

extern AVCodec ff_##x##_decoder; \

if(CONFIG_##X##_DECODER) avcodec_register(&ff_##x##_decoder); }

#define REGISTER_ENCDEC(X,x) REGISTER_ENCODER(X,x); REGISTER_DECODER(X,x)

在这里，我发现其实编码器和解码器用的注册函数都是一样的：avcodec_register()

以REGISTER_DECODER (H264, h264)为例，就是等效于

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extern AVCodec ff_h264_decoder;

if(CONFIG_H264_DECODER) avcodec_register(&ff_h264_decoder);

下面看一下avcodec_register()的源代码：

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//注册所有的AVCodec

void avcodec_register(AVCodec *codec)

{

AVCodec **p;

//初始化

avcodec_init();

//从第一个开始

p = &first_avcodec;

while (*p != NULL) p = &(*p)->next;

*p = codec;

codec->next = NULL;

if (codec->init_static_data)

codec->init_static_data(codec);

}

这段代码是比较容易理解的。首先先提一点，first_avcdec是就是AVCodec链表的头部地址，是一个全局静态变量，定义如下：

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/* encoder management */

static AVCodec *first_avcodec = NULL;

由此我们可以分析出avcodec_register()的含义，一句话概括就是：遍历链表并把当前的AVCodec加到链表的尾部。

同理，Parser，BSF（bitstream filters，比特流滤镜），HWACCEL（hardware accelerators，硬件加速器）的注册方式都是类似的。不再详述。

下面贴出它的原代码：

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/*

*雷霄骅

*leixiaohua1020@126.com

*中国传媒大学/数字电视技术

*/

/*

* Provide registration of all codecs, parsers and bitstream filters for libavcodec.

* Copyright (c) 2002 Fabrice Bellard

*

* This file is part of FFmpeg.

*

* FFmpeg 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.

*

* FFmpeg 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 FFmpeg; if not, write to the Free Software

* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

*/

/**

* @file

* Provide registration of all codecs, parsers and bitstream filters for libavcodec.

*/

#include "avcodec.h"

//硬件加速

#define REGISTER_HWACCEL(X,x) { \

extern AVHWAccel ff_##x##_hwaccel; \

if(CONFIG_##X##_HWACCEL) av_register_hwaccel(&ff_##x##_hwaccel); }

#define REGISTER_ENCODER(X,x) { \

extern AVCodec ff_##x##_encoder; \

if(CONFIG_##X##_ENCODER) avcodec_register(&ff_##x##_encoder); }

//定义的宏？宏的速度会快一点？注册AVCodec

//extern AVCodec ff_##x##_decoder;

//注意：extern表明全局唯一

//在h264中，对应的就是ff_h264_decoder

//由此可见AVCodecParser的名字是固定的

#define REGISTER_DECODER(X,x) { \

extern AVCodec ff_##x##_decoder; \

if(CONFIG_##X##_DECODER) avcodec_register(&ff_##x##_decoder); }

#define REGISTER_ENCDEC(X,x) REGISTER_ENCODER(X,x); REGISTER_DECODER(X,x)

//定义的宏？宏的速度会快一点？注册AVCodecParser

//extern AVCodecParser ff_##x##_parser;

//在h264中，对应的就是ff_h264_parser

//由此可见AVCodecParser的名字是固定的

#define REGISTER_PARSER(X,x) { \

extern AVCodecParser ff_##x##_parser; \

if(CONFIG_##X##_PARSER) av_register_codec_parser(&ff_##x##_parser); }

#define REGISTER_BSF(X,x) { \

extern AVBitStreamFilter ff_##x##_bsf; \

if(CONFIG_##X##_BSF) av_register_bitstream_filter(&ff_##x##_bsf); }

void avcodec_register_all(void)

{

static int initialized;

if (initialized)

return;

initialized = 1;

/* hardware accelerators */

REGISTER_HWACCEL (H263_VAAPI, h263_vaapi);

REGISTER_HWACCEL (H264_DXVA2, h264_dxva2);

REGISTER_HWACCEL (H264_VAAPI, h264_vaapi);

REGISTER_HWACCEL (H264_VDA, h264_vda);

REGISTER_HWACCEL (MPEG1_VDPAU, mpeg1_vdpau);

REGISTER_HWACCEL (MPEG2_DXVA2, mpeg2_dxva2);

REGISTER_HWACCEL (MPEG2_VAAPI, mpeg2_vaapi);

REGISTER_HWACCEL (MPEG2_VDPAU, mpeg2_vdpau);

REGISTER_HWACCEL (MPEG4_VAAPI, mpeg4_vaapi);

REGISTER_HWACCEL (VC1_DXVA2, vc1_dxva2);

REGISTER_HWACCEL (VC1_VAAPI, vc1_vaapi);

REGISTER_HWACCEL (WMV3_DXVA2, wmv3_dxva2);

REGISTER_HWACCEL (WMV3_VAAPI, wmv3_vaapi);

/* video codecs */

REGISTER_ENCODER (A64MULTI, a64multi);

REGISTER_ENCODER (A64MULTI5, a64multi5);

REGISTER_DECODER (AASC, aasc);

REGISTER_ENCDEC (AMV, amv);

REGISTER_DECODER (ANM, anm);

REGISTER_DECODER (ANSI, ansi);

REGISTER_ENCDEC (ASV1, asv1);

REGISTER_ENCDEC (ASV2, asv2);

REGISTER_DECODER (AURA, aura);

REGISTER_DECODER (AURA2, aura2);

REGISTER_ENCDEC (AVRP, avrp);

REGISTER_DECODER (AVS, avs);

REGISTER_DECODER (BETHSOFTVID, bethsoftvid);

REGISTER_DECODER (BFI, bfi);

REGISTER_DECODER (BINK, bink);

REGISTER_ENCDEC (BMP, bmp);

REGISTER_DECODER (BMV_VIDEO, bmv_video);

REGISTER_DECODER (C93, c93);

REGISTER_DECODER (CAVS, cavs);

REGISTER_DECODER (CDGRAPHICS, cdgraphics);

REGISTER_DECODER (CINEPAK, cinepak);

REGISTER_ENCDEC (CLJR, cljr);

REGISTER_DECODER (CSCD, cscd);

REGISTER_DECODER (CYUV, cyuv);

REGISTER_DECODER (DFA, dfa);

REGISTER_DECODER (DIRAC, dirac);

REGISTER_ENCDEC (DNXHD, dnxhd);

REGISTER_ENCDEC (DPX, dpx);

REGISTER_DECODER (DSICINVIDEO, dsicinvideo);

REGISTER_ENCDEC (DVVIDEO, dvvideo);

REGISTER_DECODER (DXA, dxa);

REGISTER_DECODER (DXTORY, dxtory);

REGISTER_DECODER (EACMV, eacmv);

REGISTER_DECODER (EAMAD, eamad);

REGISTER_DECODER (EATGQ, eatgq);

REGISTER_DECODER (EATGV, eatgv);

REGISTER_DECODER (EATQI, eatqi);

REGISTER_DECODER (EIGHTBPS, eightbps);

REGISTER_DECODER (EIGHTSVX_EXP, eightsvx_exp);

REGISTER_DECODER (EIGHTSVX_FIB, eightsvx_fib);

REGISTER_DECODER (ESCAPE124, escape124);

REGISTER_DECODER (ESCAPE130, escape130);

REGISTER_ENCDEC (FFV1, ffv1);

REGISTER_ENCDEC (FFVHUFF, ffvhuff);

REGISTER_ENCDEC (FLASHSV, flashsv);

REGISTER_ENCDEC (FLASHSV2, flashsv2);

REGISTER_DECODER (FLIC, flic);

REGISTER_ENCDEC (FLV, flv);

REGISTER_DECODER (FOURXM, fourxm);

REGISTER_DECODER (FRAPS, fraps);

REGISTER_DECODER (FRWU, frwu);

REGISTER_ENCDEC (GIF, gif);

REGISTER_ENCDEC (H261, h261);

REGISTER_ENCDEC (H263, h263);

REGISTER_DECODER (H263I, h263i);

REGISTER_ENCODER (H263P, h263p);

REGISTER_DECODER (H264, h264);

REGISTER_DECODER (H264_CRYSTALHD, h264_crystalhd);

REGISTER_DECODER (H264_VDPAU, h264_vdpau);

REGISTER_ENCDEC (HUFFYUV, huffyuv);

REGISTER_DECODER (IDCIN, idcin);

REGISTER_DECODER (IFF_BYTERUN1, iff_byterun1);

REGISTER_DECODER (IFF_ILBM, iff_ilbm);

REGISTER_DECODER (INDEO2, indeo2);

REGISTER_DECODER (INDEO3, indeo3);

REGISTER_DECODER (INDEO4, indeo4);

REGISTER_DECODER (INDEO5, indeo5);

REGISTER_DECODER (INTERPLAY_VIDEO, interplay_video);

REGISTER_ENCDEC (JPEG2000, jpeg2000);

REGISTER_ENCDEC (JPEGLS, jpegls);

REGISTER_DECODER (JV, jv);

REGISTER_DECODER (KGV1, kgv1);

REGISTER_DECODER (KMVC, kmvc);

REGISTER_DECODER (LAGARITH, lagarith);

REGISTER_ENCODER (LJPEG, ljpeg);

REGISTER_DECODER (LOCO, loco);

REGISTER_DECODER (MDEC, mdec);

REGISTER_DECODER (MIMIC, mimic);

REGISTER_ENCDEC (MJPEG, mjpeg);

REGISTER_DECODER (MJPEGB, mjpegb);

REGISTER_DECODER (MMVIDEO, mmvideo);

REGISTER_DECODER (MOTIONPIXELS, motionpixels);

REGISTER_DECODER (MPEG_XVMC, mpeg_xvmc);

REGISTER_ENCDEC (MPEG1VIDEO, mpeg1video);

REGISTER_ENCDEC (MPEG2VIDEO, mpeg2video);

REGISTER_ENCDEC (MPEG4, mpeg4);

REGISTER_DECODER (MPEG4_CRYSTALHD, mpeg4_crystalhd);

REGISTER_DECODER (MPEG4_VDPAU, mpeg4_vdpau);

REGISTER_DECODER (MPEGVIDEO, mpegvideo);

REGISTER_DECODER (MPEG_VDPAU, mpeg_vdpau);

REGISTER_DECODER (MPEG1_VDPAU, mpeg1_vdpau);

REGISTER_DECODER (MPEG2_CRYSTALHD, mpeg2_crystalhd);

REGISTER_DECODER (MSMPEG4_CRYSTALHD, msmpeg4_crystalhd);

REGISTER_DECODER (MSMPEG4V1, msmpeg4v1);

REGISTER_ENCDEC (MSMPEG4V2, msmpeg4v2);

REGISTER_ENCDEC (MSMPEG4V3, msmpeg4v3);

REGISTER_DECODER (MSRLE, msrle);

REGISTER_ENCDEC (MSVIDEO1, msvideo1);

REGISTER_DECODER (MSZH, mszh);

REGISTER_DECODER (MXPEG, mxpeg);

REGISTER_DECODER (NUV, nuv);

REGISTER_ENCDEC (PAM, pam);

REGISTER_ENCDEC (PBM, pbm);

REGISTER_ENCDEC (PCX, pcx);

REGISTER_ENCDEC (PGM, pgm);

REGISTER_ENCDEC (PGMYUV, pgmyuv);

REGISTER_DECODER (PICTOR, pictor);

REGISTER_ENCDEC (PNG, png);

REGISTER_ENCDEC (PPM, ppm);

REGISTER_ENCDEC (PRORES, prores);

REGISTER_DECODER (PRORES_LGPL, prores_lgpl);

REGISTER_DECODER (PTX, ptx);

REGISTER_DECODER (QDRAW, qdraw);

REGISTER_DECODER (QPEG, qpeg);

REGISTER_ENCDEC (QTRLE, qtrle);

REGISTER_ENCDEC (R10K, r10k);

REGISTER_ENCDEC (R210, r210);

REGISTER_ENCDEC (RAWVIDEO, rawvideo);

REGISTER_DECODER (RL2, rl2);

REGISTER_ENCDEC (ROQ, roq);

REGISTER_DECODER (RPZA, rpza);

REGISTER_ENCDEC (RV10, rv10);

REGISTER_ENCDEC (RV20, rv20);

REGISTER_DECODER (RV30, rv30);

REGISTER_DECODER (RV40, rv40);

REGISTER_DECODER (S302M, s302m);

REGISTER_ENCDEC (SGI, sgi);

REGISTER_DECODER (SMACKER, smacker);

REGISTER_DECODER (SMC, smc);

REGISTER_ENCDEC (SNOW, snow);

REGISTER_DECODER (SP5X, sp5x);

REGISTER_DECODER (SUNRAST, sunrast);

REGISTER_ENCDEC (SVQ1, svq1);

REGISTER_DECODER (SVQ3, svq3);

REGISTER_ENCDEC (TARGA, targa);

REGISTER_DECODER (THEORA, theora);

REGISTER_DECODER (THP, thp);

REGISTER_DECODER (TIERTEXSEQVIDEO, tiertexseqvideo);

REGISTER_ENCDEC (TIFF, tiff);

REGISTER_DECODER (TMV, tmv);

REGISTER_DECODER (TRUEMOTION1, truemotion1);

REGISTER_DECODER (TRUEMOTION2, truemotion2);

REGISTER_DECODER (TSCC, tscc);

REGISTER_DECODER (TXD, txd);

REGISTER_DECODER (ULTI, ulti);

REGISTER_DECODER (UTVIDEO, utvideo);

REGISTER_ENCDEC (V210, v210);

REGISTER_DECODER (V210X, v210x);

REGISTER_ENCDEC (V308, v308);

REGISTER_ENCDEC (V410, v410);

REGISTER_DECODER (VB, vb);

REGISTER_DECODER (VBLE, vble);

REGISTER_DECODER (VC1, vc1);

REGISTER_DECODER (VC1_CRYSTALHD, vc1_crystalhd);

REGISTER_DECODER (VC1_VDPAU, vc1_vdpau);

REGISTER_DECODER (VC1IMAGE, vc1image);

REGISTER_DECODER (VCR1, vcr1);

REGISTER_DECODER (VMDVIDEO, vmdvideo);

REGISTER_DECODER (VMNC, vmnc);

REGISTER_DECODER (VP3, vp3);

REGISTER_DECODER (VP5, vp5);

REGISTER_DECODER (VP6, vp6);

REGISTER_DECODER (VP6A, vp6a);

REGISTER_DECODER (VP6F, vp6f);

REGISTER_DECODER (VP8, vp8);

REGISTER_DECODER (VQA, vqa);

REGISTER_ENCDEC (WMV1, wmv1);

REGISTER_ENCDEC (WMV2, wmv2);

REGISTER_DECODER (WMV3, wmv3);

REGISTER_DECODER (WMV3_CRYSTALHD, wmv3_crystalhd);

REGISTER_DECODER (WMV3_VDPAU, wmv3_vdpau);

REGISTER_DECODER (WMV3IMAGE, wmv3image);

REGISTER_DECODER (WNV1, wnv1);

REGISTER_DECODER (XAN_WC3, xan_wc3);

REGISTER_DECODER (XAN_WC4, xan_wc4);

REGISTER_DECODER (XL, xl);

REGISTER_ENCDEC (XWD, xwd);

REGISTER_ENCDEC (Y41P, y41p);

REGISTER_DECODER (YOP, yop);

REGISTER_ENCDEC (YUV4, yuv4);

REGISTER_ENCDEC (ZLIB, zlib);

REGISTER_ENCDEC (ZMBV, zmbv);

/* audio codecs */

REGISTER_ENCDEC (AAC, aac);

REGISTER_DECODER (AAC_LATM, aac_latm);

REGISTER_ENCDEC (AC3, ac3);

REGISTER_ENCODER (AC3_FIXED, ac3_fixed);

REGISTER_ENCDEC (ALAC, alac);

REGISTER_DECODER (ALS, als);

REGISTER_DECODER (AMRNB, amrnb);

REGISTER_DECODER (AMRWB, amrwb);

REGISTER_DECODER (APE, ape);

REGISTER_DECODER (ATRAC1, atrac1);

REGISTER_DECODER (ATRAC3, atrac3);

REGISTER_DECODER (BINKAUDIO_DCT, binkaudio_dct);

REGISTER_DECODER (BINKAUDIO_RDFT, binkaudio_rdft);

REGISTER_DECODER (BMV_AUDIO, bmv_audio);

REGISTER_DECODER (COOK, cook);

REGISTER_ENCDEC (DCA, dca);

REGISTER_DECODER (DSICINAUDIO, dsicinaudio);

REGISTER_ENCDEC (EAC3, eac3);

REGISTER_DECODER (FFWAVESYNTH, ffwavesynth);

REGISTER_ENCDEC (FLAC, flac);

REGISTER_ENCDEC (G723_1, g723_1);

REGISTER_DECODER (G729, g729);

REGISTER_DECODER (GSM, gsm);

REGISTER_DECODER (GSM_MS, gsm_ms);

REGISTER_DECODER (IMC, imc);

REGISTER_DECODER (MACE3, mace3);

REGISTER_DECODER (MACE6, mace6);

REGISTER_DECODER (MLP, mlp);

REGISTER_DECODER (MP1, mp1);

REGISTER_DECODER (MP1FLOAT, mp1float);

REGISTER_ENCDEC (MP2, mp2);

REGISTER_DECODER (MP2FLOAT, mp2float);

REGISTER_DECODER (MP3, mp3);

REGISTER_DECODER (MP3FLOAT, mp3float);

REGISTER_DECODER (MP3ADU, mp3adu);

REGISTER_DECODER (MP3ADUFLOAT, mp3adufloat);

REGISTER_DECODER (MP3ON4, mp3on4);

REGISTER_DECODER (MP3ON4FLOAT, mp3on4float);

REGISTER_DECODER (MPC7, mpc7);

REGISTER_DECODER (MPC8, mpc8);

REGISTER_ENCDEC (NELLYMOSER, nellymoser);

REGISTER_DECODER (QCELP, qcelp);

REGISTER_DECODER (QDM2, qdm2);

REGISTER_ENCDEC (RA_144, ra_144);

REGISTER_DECODER (RA_288, ra_288);

REGISTER_DECODER (SHORTEN, shorten);

REGISTER_DECODER (SIPR, sipr);

REGISTER_DECODER (SMACKAUD, smackaud);

REGISTER_ENCDEC (SONIC, sonic);

REGISTER_ENCODER (SONIC_LS, sonic_ls);

REGISTER_DECODER (TRUEHD, truehd);

REGISTER_DECODER (TRUESPEECH, truespeech);

REGISTER_DECODER (TTA, tta);

REGISTER_DECODER (TWINVQ, twinvq);

REGISTER_DECODER (VMDAUDIO, vmdaudio);

REGISTER_ENCDEC (VORBIS, vorbis);

REGISTER_DECODER (WAVPACK, wavpack);

REGISTER_DECODER (WMALOSSLESS, wmalossless);

REGISTER_DECODER (WMAPRO, wmapro);

REGISTER_ENCDEC (WMAV1, wmav1);

REGISTER_ENCDEC (WMAV2, wmav2);

REGISTER_DECODER (WMAVOICE, wmavoice);

REGISTER_DECODER (WS_SND1, ws_snd1);

/* PCM codecs */

REGISTER_ENCDEC (PCM_ALAW, pcm_alaw);

REGISTER_DECODER (PCM_BLURAY, pcm_bluray);

REGISTER_DECODER (PCM_DVD, pcm_dvd);

REGISTER_ENCDEC (PCM_F32BE, pcm_f32be);

REGISTER_ENCDEC (PCM_F32LE, pcm_f32le);

REGISTER_ENCDEC (PCM_F64BE, pcm_f64be);

REGISTER_ENCDEC (PCM_F64LE, pcm_f64le);

REGISTER_DECODER (PCM_LXF, pcm_lxf);

REGISTER_ENCDEC (PCM_MULAW, pcm_mulaw);

REGISTER_ENCDEC (PCM_S8, pcm_s8);

REGISTER_DECODER (PCM_S8_PLANAR, pcm_s8_planar);

REGISTER_ENCDEC (PCM_S16BE, pcm_s16be);

REGISTER_ENCDEC (PCM_S16LE, pcm_s16le);

REGISTER_DECODER (PCM_S16LE_PLANAR, pcm_s16le_planar);

REGISTER_ENCDEC (PCM_S24BE, pcm_s24be);

REGISTER_ENCDEC (PCM_S24DAUD, pcm_s24daud);

REGISTER_ENCDEC (PCM_S24LE, pcm_s24le);

REGISTER_ENCDEC (PCM_S32BE, pcm_s32be);

REGISTER_ENCDEC (PCM_S32LE, pcm_s32le);

REGISTER_ENCDEC (PCM_U8, pcm_u8);

REGISTER_ENCDEC (PCM_U16BE, pcm_u16be);

REGISTER_ENCDEC (PCM_U16LE, pcm_u16le);

REGISTER_ENCDEC (PCM_U24BE, pcm_u24be);

REGISTER_ENCDEC (PCM_U24LE, pcm_u24le);

REGISTER_ENCDEC (PCM_U32BE, pcm_u32be);

REGISTER_ENCDEC (PCM_U32LE, pcm_u32le);

REGISTER_DECODER (PCM_ZORK , pcm_zork);

/* DPCM codecs */

REGISTER_DECODER (INTERPLAY_DPCM, interplay_dpcm);

REGISTER_ENCDEC (ROQ_DPCM, roq_dpcm);

REGISTER_DECODER (SOL_DPCM, sol_dpcm);

REGISTER_DECODER (XAN_DPCM, xan_dpcm);

/* ADPCM codecs */

REGISTER_DECODER (ADPCM_4XM, adpcm_4xm);

REGISTER_ENCDEC (ADPCM_ADX, adpcm_adx);

REGISTER_DECODER (ADPCM_CT, adpcm_ct);

REGISTER_DECODER (ADPCM_EA, adpcm_ea);

REGISTER_DECODER (ADPCM_EA_MAXIS_XA, adpcm_ea_maxis_xa);

REGISTER_DECODER (ADPCM_EA_R1, adpcm_ea_r1);

REGISTER_DECODER (ADPCM_EA_R2, adpcm_ea_r2);

REGISTER_DECODER (ADPCM_EA_R3, adpcm_ea_r3);

REGISTER_DECODER (ADPCM_EA_XAS, adpcm_ea_xas);

REGISTER_ENCDEC (ADPCM_G722, adpcm_g722);

REGISTER_ENCDEC (ADPCM_G726, adpcm_g726);

REGISTER_DECODER (ADPCM_IMA_AMV, adpcm_ima_amv);

REGISTER_DECODER (ADPCM_IMA_APC, adpcm_ima_apc);

REGISTER_DECODER (ADPCM_IMA_DK3, adpcm_ima_dk3);

REGISTER_DECODER (ADPCM_IMA_DK4, adpcm_ima_dk4);

REGISTER_DECODER (ADPCM_IMA_EA_EACS, adpcm_ima_ea_eacs);

REGISTER_DECODER (ADPCM_IMA_EA_SEAD, adpcm_ima_ea_sead);

REGISTER_DECODER (ADPCM_IMA_ISS, adpcm_ima_iss);

REGISTER_ENCDEC (ADPCM_IMA_QT, adpcm_ima_qt);

REGISTER_DECODER (ADPCM_IMA_SMJPEG, adpcm_ima_smjpeg);

REGISTER_ENCDEC (ADPCM_IMA_WAV, adpcm_ima_wav);

REGISTER_DECODER (ADPCM_IMA_WS, adpcm_ima_ws);

REGISTER_ENCDEC (ADPCM_MS, adpcm_ms);

REGISTER_DECODER (ADPCM_SBPRO_2, adpcm_sbpro_2);

REGISTER_DECODER (ADPCM_SBPRO_3, adpcm_sbpro_3);

REGISTER_DECODER (ADPCM_SBPRO_4, adpcm_sbpro_4);

REGISTER_ENCDEC (ADPCM_SWF, adpcm_swf);

REGISTER_DECODER (ADPCM_THP, adpcm_thp);

REGISTER_DECODER (ADPCM_XA, adpcm_xa);

REGISTER_ENCDEC (ADPCM_YAMAHA, adpcm_yamaha);

/* subtitles */

REGISTER_ENCDEC (ASS, ass);

REGISTER_ENCDEC (DVBSUB, dvbsub);

REGISTER_ENCDEC (DVDSUB, dvdsub);

REGISTER_DECODER (PGSSUB, pgssub);

REGISTER_ENCDEC (SRT, srt);

REGISTER_ENCDEC (XSUB, xsub);

/* external libraries */

REGISTER_ENCODER (LIBAACPLUS, libaacplus);

REGISTER_DECODER (LIBCELT, libcelt);

REGISTER_ENCDEC (LIBDIRAC, libdirac);

REGISTER_ENCODER (LIBFAAC, libfaac);

REGISTER_ENCDEC (LIBGSM, libgsm);

REGISTER_ENCDEC (LIBGSM_MS, libgsm_ms);

REGISTER_ENCODER (LIBMP3LAME, libmp3lame);

REGISTER_ENCDEC (LIBOPENCORE_AMRNB, libopencore_amrnb);

REGISTER_DECODER (LIBOPENCORE_AMRWB, libopencore_amrwb);

REGISTER_ENCDEC (LIBOPENJPEG, libopenjpeg);

REGISTER_ENCDEC (LIBSCHROEDINGER, libschroedinger);

REGISTER_ENCDEC (LIBSPEEX, libspeex);

REGISTER_DECODER (LIBSTAGEFRIGHT_H264, libstagefright_h264);

REGISTER_ENCODER (LIBTHEORA, libtheora);

REGISTER_DECODER (LIBUTVIDEO, libutvideo);

REGISTER_ENCODER (LIBVO_AACENC, libvo_aacenc);

REGISTER_ENCODER (LIBVO_AMRWBENC, libvo_amrwbenc);

REGISTER_ENCODER (LIBVORBIS, libvorbis);

REGISTER_ENCDEC (LIBVPX, libvpx);

REGISTER_ENCODER (LIBX264, libx264);

REGISTER_ENCODER (LIBX264RGB, libx264rgb);

REGISTER_ENCODER (LIBXAVS, libxavs);

REGISTER_ENCODER (LIBXVID, libxvid);

/* text */

REGISTER_DECODER (BINTEXT, bintext);

REGISTER_DECODER (XBIN, xbin);

REGISTER_DECODER (IDF, idf);

/* parsers */

REGISTER_PARSER (AAC, aac);

REGISTER_PARSER (AAC_LATM, aac_latm);

REGISTER_PARSER (AC3, ac3);

REGISTER_PARSER (ADX, adx);

REGISTER_PARSER (CAVSVIDEO, cavsvideo);

REGISTER_PARSER (DCA, dca);

REGISTER_PARSER (DIRAC, dirac);

REGISTER_PARSER (DNXHD, dnxhd);

REGISTER_PARSER (DVBSUB, dvbsub);

REGISTER_PARSER (DVDSUB, dvdsub);

REGISTER_PARSER (FLAC, flac);

REGISTER_PARSER (GSM, gsm);

REGISTER_PARSER (H261, h261);

REGISTER_PARSER (H263, h263);

REGISTER_PARSER (H264, h264);

REGISTER_PARSER (MJPEG, mjpeg);

REGISTER_PARSER (MLP, mlp);

REGISTER_PARSER (MPEG4VIDEO, mpeg4video);

REGISTER_PARSER (MPEGAUDIO, mpegaudio);

REGISTER_PARSER (MPEGVIDEO, mpegvideo);

REGISTER_PARSER (PNM, pnm);

REGISTER_PARSER (RV30, rv30);

REGISTER_PARSER (RV40, rv40);

REGISTER_PARSER (VC1, vc1);

REGISTER_PARSER (VP3, vp3);

REGISTER_PARSER (VP8, vp8);

/* bitstream filters */

REGISTER_BSF (AAC_ADTSTOASC, aac_adtstoasc);

REGISTER_BSF (CHOMP, chomp);

REGISTER_BSF (DUMP_EXTRADATA, dump_extradata);

REGISTER_BSF (H264_MP4TOANNEXB, h264_mp4toannexb);

REGISTER_BSF (IMX_DUMP_HEADER, imx_dump_header);

REGISTER_BSF (MJPEG2JPEG, mjpeg2jpeg);

REGISTER_BSF (MJPEGA_DUMP_HEADER, mjpega_dump_header);

REGISTER_BSF (MP3_HEADER_COMPRESS, mp3_header_compress);

REGISTER_BSF (MP3_HEADER_DECOMPRESS, mp3_header_decompress);

REGISTER_BSF (MOV2TEXTSUB, mov2textsub);

REGISTER_BSF (NOISE, noise);

REGISTER_BSF (REMOVE_EXTRADATA, remove_extradata);

REGISTER_BSF (TEXT2MOVSUB, text2movsub);

}

整个代码的过程就是首先确定是不是已经初始化过了（initialized），如果没有，就注册，注册，注册...直到完成所有注册。