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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
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前一阵子看了一下ffmpeg的源代码,并且做了一些注释,在此贴出来以作备忘。
本文分析一下ffmpeg注册复用器,编码器等的函数av_register_all()。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,才能使用复用器,编码器等。
可见解复用器注册都是用
REGISTER_DEMUXER (X,x)
例如:
REGISTER_DEMUXER (AAC, aac)
可见复用器注册都是用
REGISTER_MUXER (X,x))
例如:
REGISTER_MUXER (ADTS, adts)
既有解复用器又有复用器的话,可以用
REGISTER_MUXDEMUX (X,x));
例如:
REGISTER_MUXDEMUX (AC3, ac3);
我们来看一下宏的定义,这里以解复用器为例:
- #define REGISTER_DEMUXER(X,x) { \
- extern AVInputFormat ff_##x##_demuxer; \
- if(CONFIG_##X##_DEMUXER) av_register_input_format(&ff_##x##_demuxer); }
注意:define里面的##可能不太常见,它的含义就是拼接两个字符串,比如
#define Conn(x,y) x##y
那么
int n = Conn(123,456); 结果就是n=123456;
我们以REGISTER_DEMUXER (AAC, aac)为例,则它等效于
- extern AVInputFormat ff_aac_demuxer;
- if(CONFIG_AAC_DEMUXER) av_register_input_format(&ff_aac_demuxer);
从上面这段代码我们可以看出,真正注册的函数是av_register_input_format(&ff_aac_demuxer),那我就看看这个和函数的作用,查看一下av_register_input_format()的代码:
- void av_register_input_format(AVInputFormat *format)
- {
- AVInputFormat **p;
- p = &first_iformat;
- while (*p != NULL) p = &(*p)->next;
- *p = format;
- format->next = NULL;
- }
这段代码是比较容易理解的,首先先提一点,first_iformat是个什么东东呢?其实它是Input Format链表的头部地址,是一个全局静态变量,定义如下:
-
- static AVInputFormat *first_iformat = NULL;
由此我们可以分析出av_register_input_format()的含义,一句话概括就是:遍历链表并把当前的Input Format加到链表的尾部。
至此REGISTER_DEMUXER (X, x)分析完毕。
同理,复用器道理是一样的,只是注册函数改为av_register_output_format();
既有解复用器又有复用器的话,有一个宏定义:
- #define REGISTER_MUXDEMUX(X,x) REGISTER_MUXER(X,x); REGISTER_DEMUXER(X,x)
可见是分别注册了复用器和解复用器。
此外还有网络协议的注册,注册函数为ffurl_register_protocol(),在此不再详述。
下面贴出它的源代码(allformats.c)
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- #include "avformat.h"
- #include "rtp.h"
- #include "rdt.h"
- #include "url.h"
-
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- #define REGISTER_MUXER(X,x) { \
- extern AVOutputFormat ff_##x##_muxer; \
- if(CONFIG_##X##_MUXER) av_register_output_format(&ff_##x##_muxer); }
-
- #define REGISTER_DEMUXER(X,x) { \
- extern AVInputFormat ff_##x##_demuxer; \
- if(CONFIG_##X##_DEMUXER) av_register_input_format(&ff_##x##_demuxer); }
-
-
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- #define REGISTER_MUXDEMUX(X,x) REGISTER_MUXER(X,x); REGISTER_DEMUXER(X,x)
-
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-
-
- #define REGISTER_PROTOCOL(X,x) { \
- extern URLProtocol ff_##x##_protocol; \
- if(CONFIG_##X##_PROTOCOL) ffurl_register_protocol(&ff_##x##_protocol, sizeof(ff_##x##_protocol)); }
-
- void av_register_all(void)
- {
- static int initialized;
-
- if (initialized)
- return;
- initialized = 1;
-
- avcodec_register_all();
-
-
- REGISTER_MUXER (A64, a64);
- REGISTER_DEMUXER (AAC, aac);
- REGISTER_MUXDEMUX (AC3, ac3);
- REGISTER_DEMUXER (ACT, act);
- REGISTER_DEMUXER (ADF, adf);
- REGISTER_MUXER (ADTS, adts);
- REGISTER_MUXDEMUX (ADX, adx);
- REGISTER_DEMUXER (AEA, aea);
- REGISTER_MUXDEMUX (AIFF, aiff);
- REGISTER_MUXDEMUX (AMR, amr);
- REGISTER_DEMUXER (ANM, anm);
- REGISTER_DEMUXER (APC, apc);
- REGISTER_DEMUXER (APE, ape);
- REGISTER_DEMUXER (APPLEHTTP, applehttp);
- REGISTER_MUXDEMUX (ASF, asf);
- REGISTER_MUXDEMUX (ASS, ass);
- REGISTER_MUXER (ASF_STREAM, asf_stream);
- REGISTER_MUXDEMUX (AU, au);
- REGISTER_MUXDEMUX (AVI, avi);
- REGISTER_DEMUXER (AVISYNTH, avisynth);
- REGISTER_MUXER (AVM2, avm2);
- REGISTER_DEMUXER (AVS, avs);
- REGISTER_DEMUXER (BETHSOFTVID, bethsoftvid);
- REGISTER_DEMUXER (BFI, bfi);
- REGISTER_DEMUXER (BINTEXT, bintext);
- REGISTER_DEMUXER (BINK, bink);
- REGISTER_MUXDEMUX (BIT, bit);
- REGISTER_DEMUXER (BMV, bmv);
- REGISTER_DEMUXER (C93, c93);
- REGISTER_MUXDEMUX (CAF, caf);
- REGISTER_MUXDEMUX (CAVSVIDEO, cavsvideo);
- REGISTER_DEMUXER (CDG, cdg);
- REGISTER_MUXER (CRC, crc);
- REGISTER_MUXDEMUX (DAUD, daud);
- REGISTER_DEMUXER (DFA, dfa);
- REGISTER_MUXDEMUX (DIRAC, dirac);
- REGISTER_MUXDEMUX (DNXHD, dnxhd);
- REGISTER_DEMUXER (DSICIN, dsicin);
- REGISTER_MUXDEMUX (DTS, dts);
- REGISTER_MUXDEMUX (DV, dv);
- REGISTER_DEMUXER (DXA, dxa);
- REGISTER_DEMUXER (EA, ea);
- REGISTER_DEMUXER (EA_CDATA, ea_cdata);
- REGISTER_MUXDEMUX (EAC3, eac3);
- REGISTER_MUXDEMUX (FFM, ffm);
- REGISTER_MUXDEMUX (FFMETADATA, ffmetadata);
- REGISTER_MUXDEMUX (FILMSTRIP, filmstrip);
- REGISTER_MUXDEMUX (FLAC, flac);
- REGISTER_DEMUXER (FLIC, flic);
- REGISTER_MUXDEMUX (FLV, flv);
- REGISTER_DEMUXER (FOURXM, fourxm);
- REGISTER_MUXER (FRAMECRC, framecrc);
- REGISTER_MUXER (FRAMEMD5, framemd5);
- REGISTER_MUXDEMUX (G722, g722);
- REGISTER_MUXDEMUX (G723_1, g723_1);
- REGISTER_DEMUXER (G729, g729);
- REGISTER_MUXER (GIF, gif);
- REGISTER_DEMUXER (GSM, gsm);
- REGISTER_MUXDEMUX (GXF, gxf);
- REGISTER_MUXDEMUX (H261, h261);
- REGISTER_MUXDEMUX (H263, h263);
- REGISTER_MUXDEMUX (H264, h264);
- REGISTER_DEMUXER (ICO, ico);
- REGISTER_DEMUXER (IDCIN, idcin);
- REGISTER_DEMUXER (IDF, idf);
- REGISTER_DEMUXER (IFF, iff);
- REGISTER_MUXDEMUX (IMAGE2, image2);
- REGISTER_MUXDEMUX (IMAGE2PIPE, image2pipe);
- REGISTER_DEMUXER (INGENIENT, ingenient);
- REGISTER_DEMUXER (IPMOVIE, ipmovie);
- REGISTER_MUXER (IPOD, ipod);
- REGISTER_MUXER (ISMV, ismv);
- REGISTER_DEMUXER (ISS, iss);
- REGISTER_DEMUXER (IV8, iv8);
- REGISTER_MUXDEMUX (IVF, ivf);
- REGISTER_DEMUXER (JV, jv);
- REGISTER_MUXDEMUX (LATM, latm);
- REGISTER_DEMUXER (LMLM4, lmlm4);
- REGISTER_DEMUXER (LOAS, loas);
- REGISTER_DEMUXER (LXF, lxf);
- REGISTER_MUXDEMUX (M4V, m4v);
- REGISTER_MUXER (MD5, md5);
- REGISTER_MUXDEMUX (MATROSKA, matroska);
- REGISTER_MUXER (MATROSKA_AUDIO, matroska_audio);
- REGISTER_MUXDEMUX (MICRODVD, microdvd);
- REGISTER_MUXDEMUX (MJPEG, mjpeg);
- REGISTER_MUXDEMUX (MLP, mlp);
- REGISTER_DEMUXER (MM, mm);
- REGISTER_MUXDEMUX (MMF, mmf);
- REGISTER_MUXDEMUX (MOV, mov);
- REGISTER_MUXER (MP2, mp2);
- REGISTER_MUXDEMUX (MP3, mp3);
- REGISTER_MUXER (MP4, mp4);
- REGISTER_DEMUXER (MPC, mpc);
- REGISTER_DEMUXER (MPC8, mpc8);
- REGISTER_MUXER (MPEG1SYSTEM, mpeg1system);
- REGISTER_MUXER (MPEG1VCD, mpeg1vcd);
- REGISTER_MUXER (MPEG1VIDEO, mpeg1video);
- REGISTER_MUXER (MPEG2DVD, mpeg2dvd);
- REGISTER_MUXER (MPEG2SVCD, mpeg2svcd);
- REGISTER_MUXER (MPEG2VIDEO, mpeg2video);
- REGISTER_MUXER (MPEG2VOB, mpeg2vob);
- REGISTER_DEMUXER (MPEGPS, mpegps);
- REGISTER_MUXDEMUX (MPEGTS, mpegts);
- REGISTER_DEMUXER (MPEGTSRAW, mpegtsraw);
- REGISTER_DEMUXER (MPEGVIDEO, mpegvideo);
- REGISTER_MUXER (MPJPEG, mpjpeg);
- REGISTER_DEMUXER (MSNWC_TCP, msnwc_tcp);
- REGISTER_DEMUXER (MTV, mtv);
- REGISTER_DEMUXER (MVI, mvi);
- REGISTER_MUXDEMUX (MXF, mxf);
- REGISTER_MUXER (MXF_D10, mxf_d10);
- REGISTER_DEMUXER (MXG, mxg);
- REGISTER_DEMUXER (NC, nc);
- REGISTER_DEMUXER (NSV, nsv);
- REGISTER_MUXER (NULL, null);
- REGISTER_MUXDEMUX (NUT, nut);
- REGISTER_DEMUXER (NUV, nuv);
- REGISTER_MUXDEMUX (OGG, ogg);
- REGISTER_MUXDEMUX (OMA, oma);
- REGISTER_MUXDEMUX (PCM_ALAW, pcm_alaw);
- REGISTER_MUXDEMUX (PCM_MULAW, pcm_mulaw);
- REGISTER_MUXDEMUX (PCM_F64BE, pcm_f64be);
- REGISTER_MUXDEMUX (PCM_F64LE, pcm_f64le);
- REGISTER_MUXDEMUX (PCM_F32BE, pcm_f32be);
- REGISTER_MUXDEMUX (PCM_F32LE, pcm_f32le);
- REGISTER_MUXDEMUX (PCM_S32BE, pcm_s32be);
- REGISTER_MUXDEMUX (PCM_S32LE, pcm_s32le);
- REGISTER_MUXDEMUX (PCM_S24BE, pcm_s24be);
- REGISTER_MUXDEMUX (PCM_S24LE, pcm_s24le);
- REGISTER_MUXDEMUX (PCM_S16BE, pcm_s16be);
- REGISTER_MUXDEMUX (PCM_S16LE, pcm_s16le);
- REGISTER_MUXDEMUX (PCM_S8, pcm_s8);
- REGISTER_MUXDEMUX (PCM_U32BE, pcm_u32be);
- REGISTER_MUXDEMUX (PCM_U32LE, pcm_u32le);
- REGISTER_MUXDEMUX (PCM_U24BE, pcm_u24be);
- REGISTER_MUXDEMUX (PCM_U24LE, pcm_u24le);
- REGISTER_MUXDEMUX (PCM_U16BE, pcm_u16be);
- REGISTER_MUXDEMUX (PCM_U16LE, pcm_u16le);
- REGISTER_MUXDEMUX (PCM_U8, pcm_u8);
- REGISTER_DEMUXER (PMP, pmp);
- REGISTER_MUXER (PSP, psp);
- REGISTER_DEMUXER (PVA, pva);
- REGISTER_DEMUXER (QCP, qcp);
- REGISTER_DEMUXER (R3D, r3d);
- REGISTER_MUXDEMUX (RAWVIDEO, rawvideo);
- REGISTER_DEMUXER (RL2, rl2);
- REGISTER_MUXDEMUX (RM, rm);
- REGISTER_MUXDEMUX (ROQ, roq);
- REGISTER_DEMUXER (RPL, rpl);
- REGISTER_MUXDEMUX (RSO, rso);
- REGISTER_MUXDEMUX (RTP, rtp);
- REGISTER_MUXDEMUX (RTSP, rtsp);
- REGISTER_MUXDEMUX (SAP, sap);
- REGISTER_DEMUXER (SBG, sbg);
- REGISTER_DEMUXER (SDP, sdp);
- #if CONFIG_RTPDEC
- av_register_rtp_dynamic_payload_handlers();
- av_register_rdt_dynamic_payload_handlers();
- #endif
- REGISTER_DEMUXER (SEGAFILM, segafilm);
- REGISTER_MUXER (SEGMENT, segment);
- REGISTER_DEMUXER (SHORTEN, shorten);
- REGISTER_DEMUXER (SIFF, siff);
- REGISTER_DEMUXER (SMACKER, smacker);
- REGISTER_MUXDEMUX (SMJPEG, smjpeg);
- REGISTER_DEMUXER (SOL, sol);
- REGISTER_MUXDEMUX (SOX, sox);
- REGISTER_MUXDEMUX (SPDIF, spdif);
- REGISTER_MUXDEMUX (SRT, srt);
- REGISTER_DEMUXER (STR, str);
- REGISTER_MUXDEMUX (SWF, swf);
- REGISTER_MUXER (TG2, tg2);
- REGISTER_MUXER (TGP, tgp);
- REGISTER_DEMUXER (THP, thp);
- REGISTER_DEMUXER (TIERTEXSEQ, tiertexseq);
- REGISTER_MUXER (MKVTIMESTAMP_V2, mkvtimestamp_v2);
- REGISTER_DEMUXER (TMV, tmv);
- REGISTER_MUXDEMUX (TRUEHD, truehd);
- REGISTER_DEMUXER (TTA, tta);
- REGISTER_DEMUXER (TXD, txd);
- REGISTER_DEMUXER (TTY, tty);
- REGISTER_DEMUXER (VC1, vc1);
- REGISTER_MUXDEMUX (VC1T, vc1t);
- REGISTER_DEMUXER (VMD, vmd);
- REGISTER_MUXDEMUX (VOC, voc);
- REGISTER_DEMUXER (VQF, vqf);
- REGISTER_DEMUXER (W64, w64);
- REGISTER_MUXDEMUX (WAV, wav);
- REGISTER_DEMUXER (WC3, wc3);
- REGISTER_MUXER (WEBM, webm);
- REGISTER_DEMUXER (WSAUD, wsaud);
- REGISTER_DEMUXER (WSVQA, wsvqa);
- REGISTER_MUXDEMUX (WTV, wtv);
- REGISTER_DEMUXER (WV, wv);
- REGISTER_DEMUXER (XA, xa);
- REGISTER_DEMUXER (XBIN, xbin);
- REGISTER_DEMUXER (XMV, xmv);
- REGISTER_DEMUXER (XWMA, xwma);
- REGISTER_DEMUXER (YOP, yop);
- REGISTER_MUXDEMUX (YUV4MPEGPIPE, yuv4mpegpipe);
-
-
- #if CONFIG_LIBMODPLUG
- REGISTER_DEMUXER (LIBMODPLUG, libmodplug);
- #endif
- REGISTER_MUXDEMUX (LIBNUT, libnut);
-
-
-
- REGISTER_PROTOCOL (APPLEHTTP, applehttp);
- REGISTER_PROTOCOL (CACHE, cache);
- REGISTER_PROTOCOL (CONCAT, concat);
- REGISTER_PROTOCOL (CRYPTO, crypto);
- REGISTER_PROTOCOL (FILE, file);
- REGISTER_PROTOCOL (GOPHER, gopher);
- REGISTER_PROTOCOL (HTTP, http);
- REGISTER_PROTOCOL (HTTPPROXY, httpproxy);
- REGISTER_PROTOCOL (HTTPS, https);
- REGISTER_PROTOCOL (MMSH, mmsh);
- REGISTER_PROTOCOL (MMST, mmst);
- REGISTER_PROTOCOL (MD5, md5);
- REGISTER_PROTOCOL (PIPE, pipe);
- REGISTER_PROTOCOL (RTMP, rtmp);
-
- #if CONFIG_LIBRTMP
- REGISTER_PROTOCOL (RTMP, rtmpt);
- REGISTER_PROTOCOL (RTMP, rtmpe);
- REGISTER_PROTOCOL (RTMP, rtmpte);
- REGISTER_PROTOCOL (RTMP, rtmps);
- #endif
- REGISTER_PROTOCOL (RTP, rtp);
- REGISTER_PROTOCOL (TCP, tcp);
- REGISTER_PROTOCOL (TLS, tls);
- REGISTER_PROTOCOL (UDP, udp);
- }
整个代码没太多可说的,首先确定是不是已经初始化过了(initialized),如果没有,就调用avcodec_register_all()注册编解码器(这个先不分析),然后就是注册,注册,注册...直到完成所有注册。
PS:曾经研究过一阵子RTMP协议,以及对应的开源工程librtmp。在这里发现有一点值得注意,ffmpeg自带了RTMP协议的支持,只有使用 rtmpt://, rtmpe://, rtmpte://等的时候才会使用librtmp库。
函数调用关系图如下图所示。av_register_all()调用了avcodec_register_all()。avcodec_register_all()注册了和编解码器有关的组件:硬件加速器,解码器,编码器,Parser,Bitstream Filter。av_register_all()除了调用avcodec_register_all()之外,还注册了复用器,解复用器,协议处理器。
![](https://img-blog.csdn.net/20141109152923350?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvbGVpeGlhb2h1YTEwMjA=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast)
下面附上复用器,解复用器,协议处理器的代码。
注册复用器的函数是av_register_output_format()。
- void av_register_output_format(AVOutputFormat *format)
- {
- AVOutputFormat **p;
- p = &first_oformat;
- while (*p != NULL) p = &(*p)->next;
- *p = format;
- format->next = NULL;
- }
注册解复用器的函数是av_register_input_format()。
- void av_register_input_format(AVInputFormat *format)
- {
- AVInputFormat **p;
- p = &first_iformat;
- while (*p != NULL) p = &(*p)->next;
- *p = format;
- format->next = NULL;
- }
注册协议处理器的函数是ffurl_register_protocol()。
- int ffurl_register_protocol(URLProtocol *protocol)
- {
- URLProtocol **p;
- p = &first_protocol;
- while (*p)
- p = &(*p)->next;
- *p = protocol;
- protocol->next = NULL;
- return 0;
- }
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