Linux下MIPS平台交叉编译FFMpeg库 及使用库截取视频中的某一帧
参考http://www.ffmpeg.com.cn网站
一.Linux下MIPS平台交叉编译FFMpeg库:
1.下载ffmpeg库的源代码
(http://sourceforge.net/project/showfiles.php?group_id=205275&package_id=248632):
[root@localhost ffmpeg]# ls
ffmpeg-laster.tar.gz
2.解压:
[root@localhost ffmpeg]# tar zxvf ffmpeg-laster.tar.gz
3.开始配置，并编译:
[root@localhost ffmpeg]# mkdir ffmpeg-release
[root@localhost ffmpeg]# cd ffmpeg
[root@localhost ffmpeg]# ./configure --enable-cross-compile --target-os=linux --cross-prefix=mipsel-linux- --cc=mipsel-linux-gcc --enable-shared --arch=mips --prefix=/opt/brcm/ffmpeg/ffmpeg-release
[root@localhost ffmpeg]# make
[root@localhost ffmpeg]# make install
[root@localhost ffmpeg]# cd ../ffmpeg-release
[root@localhost ffmpeg-release]# tar -zcvf ffjpeg_lib.tar.gz ./lib
板子上运行:
# cp ffjpeg_lib.tar.gz /usr/local/lib/
# cd /usr/local/lib/
# tar -zxvf ffjpeg_lib.tar.gz -C ../
# rm ffjpeg_lib.tar.gz
# cp ffmpeg-release/bin/* /bin/
# ffmpeg
FFmpeg version SVN-r21694, Copyright (c) 2000-2010 Fabrice Bellard, et al.
built on Nov 17 2012 02:25:17 with gcc 4.5.3
configuration: --enable-cross-compile --target-os=linux --cross-prefix=mipsel-linux- --cc=mipsel-linux-gcc --enable-shared --arch=mips --prefix=/opt/brcm/ffmpeg/ffmpeg-release
libavutil 50. 9. 0 / 50. 9. 0
libavcodec 52.52. 0 / 52.52. 0
libavformat 52.51. 0 / 52.51. 0
libavdevice 52. 2. 0 / 52. 2. 0
libswscale 0.10. 0 / 0.10. 0
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
Use -h to get full help or, even better, run 'man ffmpeg'
#
到现在为止， 我们就成功的将 ffmpeg 移植到我们的开发板上了。
二.Linux下使用ffmpeg库:
1.命令行使用:
ffmpeg -i test.mp4 -y -f image2 -ss 30 -s 95*95 -vframes 1 a.jpg
找一个MP4文件:test.mp4,然后使用上面的命令就可以取得30秒时视频的图像，保存为
95*95像素的JPG文件。
ffmpeg -i 000094.mp4 -vframes 30 -pix_fmt rgb24 -y -f gif a.gif
把前30帧转化为GIF文件。
2.在程序中调用函数截获视频图片:
首先加入库支持，在我们的可执行程序的Makefile文件中，加入:
CFLAGS += -I/opt/brcm/ffmpeg/ffmpeg-release/include/
LFLAGS += -L/opt/brcm/ffmpeg/ffmpeg-release/lib/ -lavutil -lavformat -lavcodec -lswscale
(记住，后面最后四个参数缺一不可，否则编译不通过)
然后关于在编程中使用FFMPEG库的方法，附带一个成熟的Demo。
(test_snap.c和Makefile)
三.遇到的问题:
1.找不到关键帧：first frame is no keyframe: 这样的截图为透明色，不满足截图要求。
解决方案: 跟踪截图函数的返回值，如果no keyframe,将开始时间推迟1秒，再截图，直到成功为止。
test_snap.c 如下:
#include <stdlib.h>#include <stdio.h>#include <string.h>#include <math.h>#include <libavformat/avformat.h>#include <libswscale/swscale.h>#undef sprintf#undef uint8_t#undef uint16_t#undef uint32_t#define uint8_t unsigned char#define uint16_t unsigned short#define uint32_t unsigned long#pragma pack(2)typedef struct BMPHeader{ uint16_t identifier; uint32_t file_size; uint32_t reserved; uint32_t data_offset;} BMPHeader;typedef struct BMPMapInfo{ uint32_t header_size; uint32_t width; uint32_t height; uint16_t n_planes; uint16_t bits_per_pixel; uint32_t compression; uint32_t data_size; uint32_t hresolution; uint32_t vresolution; uint32_t n_colors_used; uint32_t n_important_colors;}BMPMapInfo;int CreateBmpImg(AVFrame *pFrame, int width, int height, int iFrame){ BMPHeader bmpheader; BMPMapInfo bmpinfo; FILE *fp; int y; char filename[32]; // Open file memset(filename, 0x0, sizeof(filename)); sprintf(filename, "%d.bmp", iFrame+1);JPRINTF(("Create BMP File : [%s] \n",filename)); fp = fopen(filename, "wb"); if(!fp)return -1; bmpheader.identifier = ('M'<<8)|'B'; bmpheader.reserved = 0; bmpheader.data_offset = sizeof(BMPHeader) + sizeof(BMPMapInfo); bmpheader.file_size = bmpheader.data_offset + width*height*24/8; bmpinfo.header_size = sizeof(BMPMapInfo); bmpinfo.width = width; bmpinfo.height = height; bmpinfo.n_planes = 1; bmpinfo.bits_per_pixel = 24; bmpinfo.compression = 0; bmpinfo.data_size = height*((width*3 + 3) & ~3); bmpinfo.hresolution = 0; bmpinfo.vresolution = 0; bmpinfo.n_colors_used = 0; bmpinfo.n_important_colors = 0; fwrite(&bmpheader,sizeof(BMPHeader),1,fp); fwrite(&bmpinfo,sizeof(BMPMapInfo),1,fp); for(y=height-1; y>=0; y--) fwrite(pFrame->data[0]+y*pFrame->linesize[0], 1, width*3, fp); fclose(fp); return 0;}//解码指定videostream，并保存frame数据到pFrame上//返回: 0--成功，非0--失败int DecodeVideoFrame(AVFormatContext *pFormatCtx, AVCodecContext *pCodecCtx, int videoStream, int64_t endtime, AVFrame *pFrame, int *keyframe_err){ static AVPacket packet; static uint8_t *rawData; static int bytesRemaining = 0; int bytesDecoded; int frameFinished; static int firstTimeFlag = 1;int snap_cnt=0;*keyframe_err=0; if (firstTimeFlag) { firstTimeFlag = 0; packet.data = NULL;//第一次解frame，初始化packet.data为null } while (1) { do { if (packet.data == NULL) av_free_packet(&packet); //释放旧的packet if (av_read_frame(pFormatCtx, &packet) < 0) { //从frame读取数据保存到packet上，<0表明到了stream end printf("-->av_read_frame end\n"); goto exit_decode; } } while (packet.stream_index != videoStream); //判断当前frame是否为指定的video stream //判断当前帧是否到达了endtime，是则返回false，停止取下一帧 if (packet.pts >= endtime) return -1; bytesRemaining = packet.size; rawData = packet.data; while (bytesRemaining > 0) { ++snap_cnt; bytesDecoded = avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, rawData, bytesRemaining); if (bytesDecoded < 0) return -1; bytesRemaining -= bytesDecoded; rawData += bytesDecoded;// if (frameFinished) return 0;if (frameFinished) {if(snap_cnt<=1) *keyframe_err=1; return 0;} } }exit_decode: bytesDecoded = avcodec_decode_video(pCodecCtx, pFrame, &frameFinished, rawData, bytesRemaining); if(packet.data != NULL) av_free_packet(&packet); if (frameFinished != 0) return 0; return -1;}void usage(const char *function){ printf("Usage: %s [File Name] [Start Time] [End Time]\n", function); printf("Ex: ./railgun panda.mpg 003005 003010\n"); printf("Time Format: HrsMinsSecs. Ex 003005 means 00 hours 30 minutes 05 senconds\n"); printf("\n");}void ParseTime(IN ulong snap_start_time, int64_t *pStartSec, IN ulong snap_end_time, int64_t *pEndSec){ int64_t starttime = 0, endtime = 0; if (pStartSec) { starttime = snap_start_time; *pStartSec = (3600*starttime/10000) + \ (60*(starttime%10000)/100) + \ (starttime%100); } if (pEndSec) { endtime = snap_end_time; *pEndSec = (3600*endtime/10000) + \ (60*(endtime%10000)/100) + \ (endtime%100); }}int __navi_snap_mtv_file(IN char *snap_file_name, IN ulong snap_start_time, IN ulong snap_end_time,IN int snap_w, IN int snap_h){//RINTF(("Open snap_file_name == [%s] \n",snap_file_name)); const char *filename; AVFormatContext *ic = NULL; AVCodecContext *dec = NULL; AVCodec *codec = NULL; AVFrame *frame = NULL; AVFrame *frameRGB = NULL; uint8_t *buffer = NULL; int numBytes; int i, videoStream; int64_t startTime = 0; int64_t endTime = 0;int keyframe_err=0; static struct SwsContext *img_convert_ctx = NULL; // Register all formats and codecs av_register_all(); filename = snap_file_name; // parse begin time and end time ParseTime(snap_start_time, &startTime, NULL, NULL); ParseTime(snap_start_time, &startTime, snap_end_time, &endTime); startTime *= AV_TIME_BASE; endTime *= AV_TIME_BASE; // Open video file if(av_open_input_file(&ic, filename, NULL, 0, NULL)!=0) { printf("Cannt open input file\n"); goto exit_err; } // Retrieve stream information if(av_find_stream_info(ic)<0) { printf("Cannt find stream info\n"); goto exit_err; } // Dump information about file onto standard error dump_format(ic, 0, filename, 0); // Find the first video stream videoStream=-1; for(i=0; i<ic->nb_streams; i++) if(ic->streams[i]->codec->codec_type==CODEC_TYPE_VIDEO) { videoStream=i; break; } if(videoStream==-1) { printf("No video stream\n"); goto exit_err; } // Get a pointer to the codec context for the video stream dec=ic->streams[videoStream]->codec; // Find the decoder for the video stream codec=avcodec_find_decoder(dec->codec_id); if(codec==NULL) { printf("Found no codec\n"); goto exit_err; } // Open codec if(avcodec_open(dec, codec)<0) { printf("Cannt open avcodec\n"); goto exit_err; } // Allocate video frame frame=avcodec_alloc_frame(); // Allocate an AVFrame structure frameRGB=avcodec_alloc_frame(); if(frameRGB==NULL) { av_free(frame); printf("Cannt alloc frame buffer for RGB\n"); goto exit_err; } // Determine required buffer size and allocate buffer numBytes=avpicture_get_size(PIX_FMT_RGB24, dec->width, dec->height); buffer=(uint8_t *)av_malloc(numBytes); if (!buffer) { av_free(frame); av_free(frameRGB); printf("Cannt alloc picture buffer\n"); goto exit_err; } // Assign appropriate parts of buffer to image planes in pFrameRGB avpicture_fill((AVPicture *)frameRGB, buffer, PIX_FMT_RGB24, dec->width, dec->height); img_convert_ctx = sws_getContext(dec->width, dec->height, dec->pix_fmt, snap_w, snap_h, PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL); if (img_convert_ctx == NULL) { printf("Cannot initialize the conversion context\n"); goto exit_err; } // Seek frame startTime = av_rescale_q(startTime, AV_TIME_BASE_Q, ic->streams[videoStream]->time_base); endTime = av_rescale_q(endTime, AV_TIME_BASE_Q, ic->streams[videoStream]->time_base); avformat_seek_file(ic, videoStream, INT64_MIN, startTime, startTime, 0); // Read frames and save first five frames to dist i=0; while(!DecodeVideoFrame(ic, dec, videoStream, endTime, frame, &keyframe_err)) { // Save the frame to disk i++; sws_scale(img_convert_ctx, (AVPicture*)frame->data, (AVPicture*)frame->linesize, 0, dec->height, (AVPicture*)frameRGB->data, (AVPicture*)frameRGB->linesize); if(0 == CreateBmpImg(frameRGB, snap_w, snap_h, i)) {break;// get one bmp file, we jump out; if you want get more bmp file, clear this line. } }exit_err: // Free the RGB image if (buffer) av_free(buffer); if (frameRGB) av_free(frameRGB); // Free the YUV frame if (frame) av_free(frame); // Close the codec if (dec) avcodec_close(dec); // Close the video file if (ic) av_close_input_file(ic); if (img_convert_ctx) sws_freeContext(img_convert_ctx);if(keyframe_err==1)// if first frame is no keyframe.return -1;else return 0;}
解决关键帧的代码:
if(-1 == __navi_snap_mtv_file(pXPlayTempFileName,000050,000130,96,96)){// if first frame is no keyframe.int ret=-1;for(i=0; i<30; ++i){if(0==ret) break;ret = __navi_snap_mtv_file(pXPlayTempFileName,000050+i,000130,96,96);}}
Makefile 如下:
CC = mipsel-linux-gccTARGET = test_snapCFLAGS += -I/opt/ffmpeg/ffmpeg-release/include/ LFLAGS += -L/opt/ffmpeg/ffmpeg-release/lib/ -lavutil -lavformat -lavcodec -lswscale$(TARGET):$(CC) -o $(TARGET) test_snap.c $(LFLAGS) $(CFLAGS)
附带几个我自己看过的网站:
http://ray.imiddle.net/2008/10/ffmpeg-install-and-usage/
http://blog.csdn.net/menuconfig/article/details/2600890
http://bbs.chinaunix.net/thread-1932536-1-1.html
OK，今天就这多，去找女朋友了，老板可是催的很急的说... O(∩_∩)O哈哈~