Read video file, save frame picture as ppm file

FFmpeg and SDL's learning process:
First, version information:
ffmpeg-3.0.2.tar.bz2
Sdl2-2.0.4.tar.gz
Second, the compilation process:
1, Ffmgeg of the compilation:
./configure--enable-shared--disable-yasm--prefix=/usr/local/ffmpeg
Make
Make install

2, SDL's compilation:
./configure--prefix=/usr/local/sdl
Make
Make install

3, the System environment configuration:
View/etc/ld.so.conf, known as "System shared Library Path"

Method One: The compiled SDL Dynamic library, ffmpeg dynamic library, copied to the "System shared Library path", after the replication is complete, create a soft connection.
(Call command Ldconfig after completion??? ）

Method Two: Modify/etc/ld.so.conf
Append the following two lines to the ld.so.conf file
/usr/local/ffmpeg/lib
/usr/local/sdl/lib
Call the ldconfig directive.
Ldconfig do these things are related to running the program, with the compiler to connect to the SDL library, compiled connection FFmpeg library a little relationship. Compile the time or the addition-l will have to add, do not confuse the

Method Three: Temporary environment variables
Export Ld_library_path= $LD _library_path:/usr/local/ffmpeg/lib:/usr/local/sdl/lib

Method Four: Modify the shell file:
$ VI ~/.bash_profile
Without ld_library_path words, add:
Ld_library_path=/usr/local/ffmpeg/lib:/usr/local/sdl/lib
Export Ld_library_path

If there is Ld_library_path,
Add the path after Ld_library_path.
Ld_library_path=.......:/usr/local/ffmpeg/lib:/usr/local/sdl/lib

After you finish modifying the shell file, then run
$ source ~/.bash_profile on the line.
------------------------------------------------------------------
Under the shell to try to set Ld_library_path, the following form of Setup, always error Bash:LD_LIBRARY_PATH:command not found,
Ld_library_path=/usr/local/lib
Ld_library_path = $ ld_library_path:/usr/local/lib
It may be because the system has not been set up before Ld_library_path, so change to this:
Export Ld_library_path=/usr/local/lib
Then use the Echo $LD _library_path to check if it really sets the success
------------------------------------------------------------
Third, write code, call ffmpeg dynamic Library.
Code, read the video file, save the frame picture as ppm file

#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; yFwrite (Pframe->data[0]+y*pframe->linesize[0], 1, width*3, pFile);

Close file
Fclose (PFile);
}

int main (int argc, char* argv[])
{
Avformatcontext*pformatctx;
Inti, 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;
}

Compile Instructions:
Gcc-o Test Main.c-i/usr/local/ffmpeg/include-l/usr/local/ffmpeg/lib-lavutil-lavformat-lavcodec-lswscale-lz

Sdl,ffmpeg are called by the compiler directive:
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

Read video file, save frame picture as ppm file