ffmpeg 源代码简单分析 ： avcodec_register_all()
=====================================================
FFmpeg的库函数源代码分析文章列表：
【架构图】
FFmpeg源代码结构图 - 解码
FFmpeg源代码结构图 - 编码
【通用】
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：内存的分配和释放（av_malloc()、av_free()等）
FFmpeg 源代码简单分析：常见结构体的初始化和销毁（AVFormatContext，AVFrame等）
FFmpeg 源代码简单分析：avio_open2()
FFmpeg 源代码简单分析：av_find_decoder()和av_find_encoder()
FFmpeg 源代码简单分析：avcodec_open2()
FFmpeg 源代码简单分析：avcodec_close()
【解码】
图解FFMPEG打开媒体的函数avformat_open_input
FFmpeg 源代码简单分析：avformat_open_input()
FFmpeg 源代码简单分析：avformat_find_stream_info()
FFmpeg 源代码简单分析：av_read_frame()
FFmpeg 源代码简单分析：avcodec_decode_video2()
FFmpeg 源代码简单分析：avformat_close_input()
【编码】
FFmpeg 源代码简单分析：avformat_alloc_output_context2()
FFmpeg 源代码简单分析：avformat_write_header()
FFmpeg 源代码简单分析：avcodec_encode_video()
FFmpeg 源代码简单分析：av_write_frame()
FFmpeg 源代码简单分析：av_write_trailer()
【其它】
FFmpeg源代码简单分析：日志输出系统（av_log()等）
FFmpeg源代码简单分析：结构体成员管理系统-AVClass
FFmpeg源代码简单分析：结构体成员管理系统-AVOption
FFmpeg源代码简单分析：libswscale的sws_getContext()
FFmpeg源代码简单分析：libswscale的sws_scale()
FFmpeg源代码简单分析：libavdevice的avdevice_register_all()
FFmpeg源代码简单分析：libavdevice的gdigrab
【脚本】
FFmpeg源代码简单分析：makefile
FFmpeg源代码简单分析：configure
【H.264】
FFmpeg的H.264解码器源代码简单分析：概述
=====================================================
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：
#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
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：
//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：
/* 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：
/* *雷霄骅 *[email protected] *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。
函数的调用关系图如下图所示。av_register_all()调用了avcodec_register_all()。因此如果调用过av_register_all()的话就不需要再调用avcodec_register_all()了。
下面附上硬件加速器，编码器/解码器，parser，Bitstream Filter的注册代码。
硬件加速器注册函数是av_register_hwaccel()。
void av_register_hwaccel(AVHWAccel *hwaccel)
{
AVHWAccel **p = last_hwaccel;
hwaccel->next = NULL;
while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, hwaccel))
p = &(*p)->next;
last_hwaccel = &hwaccel->next;
}
编解码器注册函数是avcodec_register()。
av_cold void avcodec_register(AVCodec *codec)
{
AVCodec **p;
avcodec_init();
p = last_avcodec;
codec->next = NULL;
while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, codec))
p = &(*p)->next;
last_avcodec = &codec->next;
if (codec->init_static_data)
codec->init_static_data(codec);
}
parser注册函数是av_register_codec_parser()。
void av_register_codec_parser(AVCodecParser *parser)
{
do {
parser->next = av_first_parser;
} while (parser->next != avpriv_atomic_ptr_cas((void * volatile *)&av_first_parser, parser->next, parser));
}
Bitstream Filter注册函数是av_register_bitstream_filter()。
void av_register_bitstream_filter(AVBitStreamFilter *bsf)
{
do {
bsf->next = first_bitstream_filter;
} while(bsf->next != avpriv_atomic_ptr_cas((void * volatile *)&first_bitstream_filter, bsf->next, bsf));
}后两个函数中的avpriv_atomic_ptr_cas()定义如下。
void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
{
if (*ptr == oldval) {
*ptr = newval;
return oldval;
}
return *ptr;
}