Ffmpeg 使用libavcodec读取.mkv视频文件
试图读取.mkv文件并将其写入.bmp,但生成的.bmp是黑白的,由多个本应写入内容的迷你图像组成:Ffmpeg 使用libavcodec读取.mkv视频文件,ffmpeg,libav,libavcodec,libavformat,Ffmpeg,Libav,Libavcodec,Libavformat,试图读取.mkv文件并将其写入.bmp,但生成的.bmp是黑白的,由多个本应写入内容的迷你图像组成: int main() { av_register_all(); avformat_network_init(); avfilter_register_all(); //crashes on -Ofast without =NULL initialization: AVFormatContext * format = NULL; if ( avfo
int main()
{
av_register_all();
avformat_network_init();
avfilter_register_all();
//crashes on -Ofast without =NULL initialization:
AVFormatContext * format = NULL;
if ( avformat_open_input( & format, VIDEO_FILE, NULL, NULL ) != 0 ) {
cerr << "Could not open file " << VIDEO_FILE << endl;
return -1;
}
// Retrieve stream information
if ( avformat_find_stream_info( format, NULL ) < 0) {
cerr << "avformat_find_stream_info() failed." << endl;
return -1;
}
av_dump_format( format, 0, VIDEO_FILE, false );
AVCodec * video_dec = (AVCodec*)1;
AVCodec * audio_dec = (AVCodec*)1;
const auto video_stream_index = av_find_best_stream( format, AVMEDIA_TYPE_VIDEO, -1, -1, & video_dec, 0 );
const auto audio_stream_index = av_find_best_stream( format, AVMEDIA_TYPE_AUDIO, -1, -1, & audio_dec, 0 );
if ( video_stream_index < 0 ) {
cerr << "Failed to find video stream." << endl;
return -1;
}
if ( audio_stream_index < 0 ) {
cerr << "Failed to find audio stream." << endl;
return -1;
}
AVCodecParameters * videoParams = format->streams[ video_stream_index ]->codecpar;
cout << "Having " << videoParams->width << " | " << videoParams->height << " video." << endl;
av_read_play( format );
// create decoding context
AVCodecContext * video_ctx = avcodec_alloc_context3( video_dec );
AVCodecContext * audio_ctx = avcodec_alloc_context3( audio_dec );
if ( ! video_ctx || ! audio_ctx ) {
cerr << "Failed to avcodec_alloc_context3()" << endl;
return -1;
}
if ( video_dec->capabilities & AV_CODEC_CAP_TRUNCATED ) video_ctx->flags |= AV_CODEC_FLAG_TRUNCATED; // we do not send complete frames
/* For some codecs, such as msmpeg4 and mpeg4, width and height
MUST be initialized there because this information is not
available in the bitstream. */
avcodec_parameters_to_context( video_ctx, format->streams[ video_stream_index ]->codecpar );
avcodec_parameters_to_context( audio_ctx, format->streams[ audio_stream_index ]->codecpar );
if ( avcodec_open2( video_ctx, video_dec, NULL ) < 0 ) {
cout << "Failed to open video decoder." << endl;
return -1;
}
if ( avcodec_open2( audio_ctx, audio_dec, NULL ) < 0 ) {
cout << "Failed to open audio decoder." << endl;
return -1;
}
uint8_t* picture_buffer = (uint8_t*) (av_malloc( avpicture_get_size( AV_PIX_FMT_RGB24 , videoParams->width, videoParams->height ) ));
AVFrame* picture = av_frame_alloc();
avpicture_fill( (AVPicture *) picture, picture_buffer, AV_PIX_FMT_RGB24, video_ctx->width, video_ctx->height );
AVPacket packet;
av_init_packet( & packet );
int cnt = 0;
while ( av_read_frame( format, & packet ) >= 0 && cnt < 10 ) {
if ( packet.stream_index == video_stream_index ) {
int check;
const auto result = avcodec_decode_video2( video_ctx, picture, & check, & packet );
cout << "Bytes decoded " << result << " check " << check << endl;
std::string name = "debug/av/";
name += std::to_string( cnt ) + ".bmp";
cout << "Writing frame " << name << " with linesize " << picture->linesize[0] << " ..." << endl;
write_bmp( (uint8_t*) picture->data, videoParams->width, videoParams->height, name.c_str() );
av_frame_unref( picture );
++ cnt;
}
else if ( packet.stream_index == audio_stream_index ) {
cout << "Sound packet" << endl;
}
av_free_packet( & packet );
av_init_packet( & packet );
}
}
intmain()
{
av_寄存器_all();
avformat_network_init();
avfilter_register_all();
//在-Ofast上崩溃,不带=NULL初始化:
AVFormatContext*格式=空;
if(avformat\u open\u输入(&format,VIDEO\u文件,NULL,NULL)!=0){
cerr您必须使用swscale将图片转换为RGB。谢谢您的回答!正如我正确理解的,图像是AV_PIX_FMT_YUV420P格式的,但如何将其转换为RGB?是否有一种方法可以通过编程确定帧格式,以便任何视频文件都可以工作?是的,请查看AVFrame的文档。它有一种格式您可以传递给swscale的值。swscale在互联网上的许多示例中也有很好的文档记录。不,我尝试使用大约10个libav示例,但都失败了,主要是因为我的Ubuntu 18.04和内核v5.4 libav太现代了。例如,我得到了最远的结果:它至少可以编译,但给出了[mpeg1video@0x55ded11f97e0]无效的帧尺寸0x0。
错误:(因此,当前正在尝试调整来自和为swsscale()构造AVFrame的样本,但获得了swscaler:错误的src图像指针
错误…。另一次尝试(记不起在哪里找到它)使用实用函数av_image_alloc()初始化AVFrame)
在if()内部失败。
。