Hi all,
To start making my hand dirty with ffmpeg, i tried to adapt the sample
available on the site to the git version of ffmpeg
(using avcodec_decode_video2, sws_alloc_context, sws_init_context and
sws_scale), but the only thing i obtain at the end is a serie of really nice
black pictures.
When viewing the file in hex format, i obtain the good values for the header
(P6.512 512.255) butthen, the the image is filled with 0x00 until the end
(which explains the black).
I must be missing something.
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
static void SaveFrame(AVFrame *pFrame, int width, int height, int iFrame);
int main(int argc, char *argv[]) {
AVFormatContext *pFormatCtx;
int i, videoStream;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
AVFrame *pFrame;
AVFrame *pFrameRGB;
AVPacket packet;
int frameFinished;
int numBytes;
uint8_t *buffer;
if(argc < 2) {
printf("Please provide a movie file\n");
return -1;
}
// Register all formats and codecs
av_register_all();
// Open video file
if(av_open_input_file(&pFormatCtx, argv[1], NULL, 0, NULL)!=0)
return -1; // Couldn't open file
// Retrieve stream information
if(av_find_stream_info(pFormatCtx)<0)
return -1; // Couldn't find stream information
// Dump information about file onto standard error
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==CODEC_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_open(pCodecCtx, pCodec)<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;
// Convert the image into YUV format that SDL uses
//if(img_convert_ctx == NULL) {
img_convert_ctx = sws_alloc_context();
av_set_int(img_convert_ctx, "srcw", pCodecCtx->width);
av_set_int(img_convert_ctx, "srch", pCodecCtx->height);
av_set_int(img_convert_ctx, "dstw", pCodecCtx->width);
av_set_int(img_convert_ctx, "dsth", pCodecCtx->height);
av_set_int(img_convert_ctx, "src_format", pCodecCtx->pix_fmt);
av_set_int(img_convert_ctx, "dst_format", PIX_FMT_RGB24);
av_set_int(img_convert_ctx, "sws_flags", SWS_BICUBIC);
av_set_int(img_convert_ctx, "src_range", 1);
av_set_int(img_convert_ctx, "dst_range", 1);
if (sws_init_context(img_convert_ctx, NULL, NULL) < 0) {
fprintf(stderr, "Cannot initialize the conversion context!\n");
exit(1);
}
//}
sws_scale(img_convert_ctx, (const uint8_t * const*)pFrame->data,
pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data,
pFrameRGB->linesize);
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
av_close_input_file(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, "test/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);
}
Thanks in advance :)
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