// avcodec_sample.0.5.0.c // A small sample program that shows how to use libavformat and libavcodec to // read video from a file. // // This version is for the 0.4.9+ release of ffmpeg. This release adds the // av_read_frame() API call, which simplifies the reading of video frames // considerably. // // Use // // gcc -o avcodec_sample.0.5.0 avcodec_sample.0.5.0.c -lavformat -lavcodec -lavutil -lswscale -lz -lbz2 // // to build (assuming libavformat, libavcodec, libavutil, and swscale are correctly installed on // your system). // // Run using // // avcodec_sample.0.5.0 myvideofile.mpg // // to write the first five frames from "myvideofile.mpg" to disk in PPM // format. #include <libavcodec/avcodec.h> #include <libavformat/avformat.h> #include <libswscale/swscale.h> #include <stdio.h> #include <stdlib.h> #include <stdbool.h> static void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame); int main (int argc, const char * argv[]) { AVFormatContext *pFormatCtx; int i, videoStream; AVCodecContext *pCodecCtx; AVCodec *pCodec; AVFrame *pFrame; AVFrame *pFrameRGB; AVPacket packet; int frameFinished; int numBytes; uint8_t *buffer; // Register all formats and codecs av_register_all(); avformat_network_init(); // Open video file if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0) return -1; // Couldn't open file // Retrieve stream information if(avformat_find_stream_info(pFormatCtx, NULL)<0) return -1; // Couldn't find stream information // Dump information about file onto standard error av_dump_format(pFormatCtx, 0, argv[1], false); // Find the first video stream videoStream=-1; for(i=0; i<pFormatCtx->nb_streams; i++) if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) { videoStream=i; break; } if(videoStream==-1) return -1; // Didn't find a video stream // Get a pointer to the codec context for the video stream pCodecCtx=pFormatCtx->streams[videoStream]->codec; // Find the decoder for the video stream pCodec=avcodec_find_decoder(pCodecCtx->codec_id); if(pCodec==NULL) return -1; // Codec not found // Open codec if(avcodec_open2(pCodecCtx, pCodec, NULL)<0) return -1; // Could not open codec // Hack to correct wrong frame rates that seem to be generated by some codecs if(pCodecCtx->time_base.num>1000 && pCodecCtx->time_base.den==1) pCodecCtx->time_base.den=1000; // Allocate video frame pFrame=avcodec_alloc_frame(); // Allocate an AVFrame structure pFrameRGB=avcodec_alloc_frame(); if(pFrameRGB==NULL) return -1; // Determine required buffer size and allocate buffer numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height); buffer=malloc(numBytes); // Assign appropriate parts of buffer to image planes in pFrameRGB avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height); // Read frames and save first five frames to disk i=0; while(av_read_frame(pFormatCtx, &packet)>=0) { // Is this a packet from the video stream? if(packet.stream_index==videoStream) { // Decode video frame avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet); // Did we get a video frame? if(frameFinished) { static struct SwsContext *img_convert_ctx; #if 0 // Older removed code // Convert the image from its native format to RGB swscale img_convert((AVPicture *)pFrameRGB, PIX_FMT_RGB24, (AVPicture*)pFrame, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height); // function template, for reference int sws_scale(struct SwsContext *context, uint8_t* src[], int srcStride[], int srcSliceY, int srcSliceH, uint8_t* dst[], int dstStride[]); #endif // Convert the image into YUV format that SDL uses if(img_convert_ctx == NULL) { int w = pCodecCtx->width; int h = pCodecCtx->height; img_convert_ctx = sws_getContext(w, h, pCodecCtx->pix_fmt, w, h, PIX_FMT_RGB24, SWS_BICUBIC, NULL, NULL, NULL); if(img_convert_ctx == NULL) { fprintf(stderr, "Cannot initialize the conversion context!\n"); exit(1); } } int ret = sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize); #if 0 // this use to be true, as of 1/2009, but apparently it is no longer true in 3/2009 if(ret) { fprintf(stderr, "SWS_Scale failed [%d]!\n", ret); exit(-1); } #endif // Save the frame to disk if(i++<=5) SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i); } } // Free the packet that was allocated by av_read_frame av_free_packet(&packet); } // Free the RGB image free(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; } static 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); }