【发布时间】：2013-01-01 04:17:07
【问题描述】：
我在Qt Mac中编译ffmpeg的例子时发现了一个奇怪的问题。
我已经安装了ffmpeg库，并在终端用cc和gcc编译器测试了这个例子，编译运行没有任何问题。
但是当我在 Qt 中调用库（ffmpeg 是 C 库）来编译示例的相同代码时，g++ 编译器给了我很多错误。
我在main.cpp代码中使用过这个结构：
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
extern "C" {
#include <libavutil/imgutils.h>
#include <libavutil/samplefmt.h>
#include <libavutil/timestamp.h>
#include <libavformat/avformat.h>
}
#include <QDebug>
编译输出给了我：
In file included from ../audvid/main.cpp:7:
/opt/local/include/libavutil/timestamp.h: In function 'char*
av_ts_make_string(char*, int64_t)':
/opt/local/include/libavutil/timestamp.h:48: warning: comparison
between signed and unsigned integer expressions
/opt/local/include/libavutil/timestamp.h:49: error: expected `)'
before 'PRId64' /opt/local/include/libavutil/timestamp.h:49: warning:
spurious trailing '%' in format
/opt/local/include/libavutil/timestamp.h:49: warning: too many
arguments for format /opt/local/include/libavutil/timestamp.h: At
global scope: /opt/local/include/libavutil/timestamp.h:68: error:
'AVRational' has not been declared
/opt/local/include/libavutil/timestamp.h: In function 'char*
av_ts_make_time_string(char*, int64_t, int*)':
/opt/local/include/libavutil/timestamp.h:70: warning: comparison
between signed and unsigned integer expressions
/opt/local/include/libavutil/timestamp.h:71: error: 'av_q2d' was not
declared in this scope ../audvid/main.cpp: In function 'int
decode_packet(int*, int)': ../audvid/main.cpp:50: error: cannot
convert 'AVRational*' to 'int*' for argument '3' to 'char*
av_ts_make_time_string(char*, int64_t, int*)' ../audvid/main.cpp:73:
error: cannot convert 'AVRational*' to 'int*' for argument '3' to
'char* av_ts_make_time_string(char*, int64_t, int*)'
../audvid/main.cpp:75: error: 'struct AVFrame' has no member named
'channels' ../audvid/main.cpp:84: error: 'struct AVFrame' has no
member named 'channels' ../audvid/main.cpp:90: error: 'struct AVFrame'
has no member named 'channels' ../audvid/main.cpp: In function 'int
open_codec_context(int*, AVFormatContext*, AVMediaType)':
../audvid/main.cpp:112: error: 'av_get_media_type_string' was not
declared in this scope ../audvid/main.cpp:123: error:
'av_get_media_type_string' was not declared in this scope
../audvid/main.cpp:129: error: 'av_get_media_type_string' was not
declared in this scope ../audvid/main.cpp: In function 'int
get_format_from_sample_fmt(const char**, AVSampleFormat)':
../audvid/main.cpp:152: warning: comparison between signed and
unsigned integer expressions ../audvid/main.cpp: In function 'int
main(int, char**)': ../audvid/main.cpp:239: error: invalid conversion
from 'void*' to 'uint8_t**' make: *** [main.o] Error 1 make: Leaving
directory
`/Users/polin/Desktop/audvid/audvid-build- Qt_4_8_0_qt_everywhere_opensource_src_4_8_0_tp-Release'
10:44:37: The process "/usr/bin/make" exited with code 2. Error while
building/deploying project audvid (target: Qt 4.8.0
(qt-everywhere-opensource-src-4.8.0-tp)) When executing step 'Make'
我不明白我是否在代码中犯了错误，或者我是否必须更改 Qt 编译器？ （我不知道怎么做）
【问题讨论】：
-
我删除了对 Qt 的引用，因为它与任何东西都没有多大关系。您可能正在使用 Qt Creator，它是一个面向 Qt 的 IDE。
-
@rubenvb .. 完全不同意 .. 很多人登陆或可能登陆这里，因为他们不知道这是一个“gcc”问题.. 他们只是在编译 Qt/C++ 时看到它