ffmpeg跟sdl的学习过程:
一、版本信息:
ffmpeg-3.0.2.tar.bz2
SDL2-2.0.4.tar.gz
二、编译过程:
1、ffmgeg的编译:
./configure --enable-shared --disable-yasm --prefix=/usr/local/ffmpeg
make
make install
2、sdl的编译:
./configure --prefix=/usr/local/sdl
make
make install
3、系统环境配置:
查看/etc/ld.so.conf,知道 ”系统共享库路径”
方法一:把编译好的sdl的动态库,ffmpeg的动态库,复制到 “系统共享库路径“ 中,复制完成后,创建好软连接。
(完成之后调用指令ldconfig ???)
方法二:修改/etc/ld.so.conf
把下面的两行追加到ld.so.conf文件中
/usr/local/ffmpeg/lib
/usr/local/sdl/lib
调用ldconfig指令。
ldconfig做的这些东西都与运行程序时有关,跟编译连接sdl库,编译连接ffmpeg库一点关系都没有。编译的时候还是该加-L就得加,不要混淆了
方法三:临时环境变量
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/ffmpeg/lib:/usr/local/sdl/lib
方法四:修改shell文件:
$ vi ~/.bash_profile
没有LD_LIBRARY_PATH的话,添加:
LD_LIBRARY_PATH=/usr/local/ffmpeg/lib:/usr/local/sdl/lib
export LD_LIBRARY_PATH
有LD_LIBRARY_PATH的话,
在LD_LIBRARY_PATH之后进行路径添加即可。
LD_LIBRARY_PATH=.......:/usr/local/ffmpeg/lib:/usr/local/sdl/lib
修改完shell文件之后,然后运行
$ source ~/.bash_profile 就行了。
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在shell下尝试设置LD_LIBRARY_PATH,以下面这种形式设置,老是报错bash: LD_LIBRARY_PATH: command not found,
LD_LIBRARY_PATH=/usr/local/lib
LD_LIBRARY_PATH = $ LD_LIBRARY_PATH:/usr/local/lib
可能是因为系统之前没有设置过LD_LIBRARY_PATH,于是改成这样:
export LD_LIBRARY_PATH=/usr/local/lib
然后用 echo $LD_LIBRARY_PATH检查一下是否真的设置成功
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三、编写代码,调用ffmpeg动态库。
代码,读取视屏文件,保存帧图片为ppm文件
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <stdio.h>
void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame)
{
FILE *pFile;
char szFilename[32];
int y;
// Open file
sprintf(szFilename, "frame%d.ppm", iFrame);
pFile=fopen(szFilename, "wb");
if(pFile==NULL)
return;
// Write header
fprintf(pFile, "P6\n%d %d\n255\n", width, height);
// Write pixel data
for(y=0; y<height; y++)
fwrite(pFrame->data[0]+y*pFrame->linesize[0], 1, width*3, pFile);
// Close file
fclose(pFile);
}
int main(int argc, char* argv[])
{
AVFormatContext *pFormatCtx;
int i, videoindex;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
av_register_all();
avformat_network_init();
pFormatCtx = avformat_alloc_context();
if(avformat_open_input(&pFormatCtx,argv[1],NULL,NULL)!=0)
{
printf("open file error\n");
return -1;
}
if ( avformat_find_stream_info(pFormatCtx,NULL) < 0 )
{
return -1;
}
i = 0;
int videostream = -1;
printf("pFormatCtx->nb_streams=%d\n", pFormatCtx->nb_streams);
for(i=0;i<pFormatCtx->nb_streams;i++)
{
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
videostream = i;
break;
}
}
printf("videostream=%d\n", videostream);
if (-1 == videostream)
{
printf("error no video stream\n");
return;
}
pCodecCtx = pFormatCtx->streams[videostream]->codec;
pCodec = avcodec_find_decoder( pCodecCtx->codec_id );
if(NULL == pCodec)
{
printf("couldn't find the decode\n");
return -1;
}
if( avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
{
printf("open decode error\n");
return -1;
}
AVFrame *pFrame,*pFrameRGB;
pFrame = av_frame_alloc();
pFrameRGB = av_frame_alloc();
uint8_t *out_buffer;
int num = avpicture_get_size(AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height);
printf("num=%d\n", num);
out_buffer = (uint8_t *)av_malloc(num*sizeof(uint8_t));
avpicture_fill((AVPicture *)pFrameRGB, out_buffer, AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height);
AVPacket packet;
int ret = -1;
i = 0;
struct SwsContext *img_convert_ctx = NULL;
img_convert_ctx = sws_getContext(pCodecCtx->width,pCodecCtx->height,pCodecCtx->pix_fmt , pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL);
while(av_read_frame(pFormatCtx, &packet)>=0)
{
//printf("i=%d, videoindex=%d, packet.stream_index=%d\n", i++, videoindex, packet.stream_index);
if(packet.stream_index == videostream)
{
//printf("111111\n");
int got_picture = -1;
ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, &packet);
if(ret < 0)
{
printf("decode error\n");
return -1;
}
//printf("got_picture:%d\n",got_picture);
if(got_picture)
{
sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
if(++i<=20)
{
SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);
}
}
}
av_free_packet(&packet);
}
free(out_buffer);
av_free(pFrameRGB);
// Free the YUV frame
av_free(pFrame);
// Close the codec
avcodec_close(pCodecCtx);
// Close the video file
avformat_close_input(&pFormatCtx);
return 0;
}
编译指令:
gcc -o test main.c -I/usr/local/ffmpeg/include -L/usr/local/ffmpeg/lib -lavutil -lavformat -lavcodec -lswscale -lz
sdl,ffmpeg都调用的编译指令:
gcc -o test main.c -I/usr/local/ffmpeg/include -I/usr/local/sdl/include -L/usr/local/ffmpeg/lib -L/usr/local/sdl/lib -lavutil -lavformat -lavcodec -lswscale -lz -lSDL2