如何使用的Qt4 libav codeC？ [英] How to use libavcodec in Qt4?
问题描述
我如何使用libav codeC在Qt4的访问单个视频帧？
How do I use libavcodec in Qt4 to access individual video frames?
验证该视频流可以通过libav $ C $立方厘米德$ C $光盘通过编译<经过href=\"http://web.me.com/dhoerl/Home/Tech_Blog/Entries/2009/1/22_Revised_av$c$cc_sample.c_files/av$c$cc_sample.0.5.0.c\"相对=nofollow>这个例子，我搬到源$ C $ C到我的C ++程序。现在 av_open_input_file（）突然无法打开我的视频文件。（返回错误code：-2）
After verifying that the video stream can be decoded by libavcodec by compiling this example, I moved the source code to my C++ program. Now av_open_input_file() is suddenly unable to open my video file (returning an errorcode: -2).
调用看起来像这样现在：
The call looks like this right now:
...
// Register all formats and codecs
avcodec_register_all();
// Open video file
QString videoFileName("/absolute/path/to/video.avi"); // from somewhere else in the application
const char* fileName = videoFileName.toStdString().c_str();
int err = 0;
if((err = av_open_input_file(&pFormatCtx, fileName, NULL, 0, NULL)) != 0)
{
doErrorHandling(err, fileName); // err = -2
}
当我在看为const char *文件名在调试器中它看起来是正确的。我在做一些基本的错误在混合C和C ++ code（我刚刚从倾倒的例子中，code到一个类的构造函数第一次尝试）？
When I look at const char* fileName inside the debugger it looks correct. Am I making some basic mistake in mixing C and C++ code (for a first attempt I just dumped the code from the example into the constructor of a class)?
注意：为了获取应用程序编译包括我这样的标题：
Note: In order to get the application to compile I include the headers like this:
extern "C"
{
#define __STDC_CONSTANT_MACROS // for UINT64_C
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
}
我也试图硬code的路径，视频文件到应用程序中没有任何成功：
I have also tried to hard code the path to the video file into the application without any success:
av_open_input_file(&pFormatCtx, "/home/bjoernz/video.avi", NULL, 0, NULL);
我是能够编译和执行使用的例子（AV codec_sample.0.5.0.c） G ++ 。
推荐答案
那么，这是尴尬的：
当我转移从这个例子给C ++应用程序我犯了一个愚蠢的错误，当我链接错误，这对我的源$ C $ C，它 av_register_all（）; 不可用......我它重命名为 AV codec_register_all（），一会儿后，我固定链接问题，忘了...
When I transfered the source code from the example to the c++ application I made a stupid mistake when I got linker errors, that told me that av_register_all(); was unavailable... and I renamed it to avcodec_register_all(), a little while later I fixed the linker problem and forgot about it...
解决方案： AV codec_register_all（）需要更改为 av_register_all（）。
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