c++ - FFmpeg H264解析

Question

我正在使用 FFmpeg 解码 H.264 视频，用于以下程序:

    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <signal.h>

    #include <sys/time.h>
    #include <time.h>

#include <libavcodec/avcodec.h>
#include <libavutil/mathematics.h>

#include <SDL/SDL.h>

void sigint_handler(int signal) {
    printf("\n");
    exit(0);
}

const char *window_title;
SDL_Surface *screen;
SDL_Overlay *yuv_overlay;

#define INBUF_SIZE 80000

/*
 * Video decoding example
 */

static long get_time_diff(struct timeval time_now) {
   struct timeval time_now2;
   gettimeofday(&time_now2,0);
   return time_now2.tv_sec*1.e6 - time_now.tv_sec*1.e6 + time_now2.tv_usec - time_now.tv_usec;
}

int video_open(AVCodecContext *avctx, const char *filename){
    int flags = SDL_HWSURFACE|SDL_ASYNCBLIT|SDL_HWACCEL;
    int w,h;

    flags |= SDL_RESIZABLE;

    if (avctx->width){
        w = avctx->width;
        h = avctx->height;
    } else {
        w = 640;
        h = 480;
    }

    if(SDL_Init(SDL_INIT_VIDEO) < 0) {
    fprintf(stderr, "SDL_INIT_VIDEO failed!\n");
    exit(1);
    }

    screen = SDL_SetVideoMode(w, h, 0, flags);

    if (!screen) {
        fprintf(stderr, "SDL: could not set video mode - exiting\n");
        return -1;
    }
    if (!window_title)
        window_title = filename;
    SDL_WM_SetCaption(window_title, window_title);

    yuv_overlay = SDL_CreateYUVOverlay(w, h, SDL_YV12_OVERLAY, screen);

    if (yuv_overlay->hw_overlay) {
    fprintf(stderr, "Using hardware overlay!\n");
    }

    return 0;
}

int main(int argc, char **argv) {
    AVCodec *codec;
    AVCodecContext *c= NULL;
    AVCodecParserContext *parser = NULL;
    int frame, got_picture, len2, len;
    const char *filename;
    FILE *f;
    AVFrame *picture;
    char *arghwtf = malloc(INBUF_SIZE);
    char *luma = NULL;
    char *chroma = NULL;
    int i=0;
    uint64_t in_len;
    int pts, dts;
    struct timeval t;
    float inv_fps = 1e6/23.98;
    AVPacket avpkt;
    SDL_Rect rect;


    /* register all the codecs */
    avcodec_register_all();

    filename = argv[1];

    av_init_packet(&avpkt);

    printf("Decoding file %s...\n", filename);

    /* find the H.264 video decoder */
    codec = avcodec_find_decoder(CODEC_ID_H264);
    if (!codec) {
        fprintf(stderr, "codec not found\n");
        exit(1);
    }

    c = avcodec_alloc_context3(codec);
    picture = avcodec_alloc_frame();

    c->skip_loop_filter = 48; // skiploopfilter=all

    if (avcodec_open(c, codec) < 0) {
        fprintf(stderr, "could not open codec\n");
        exit(1);
    }

    /* the codec gives us the frame size, in samples */
    parser = av_parser_init(c->codec_id);
    parser->flags |= PARSER_FLAG_ONCE;

    f = fopen(filename, "rb");
    if (!f) {
        fprintf(stderr, "could not open %s\n", filename);
        exit(1);
    }

    frame = 0;
    gettimeofday(&t, 0);
    if(fread(arghwtf, 1, INBUF_SIZE, f) == 0) {
    exit(1);
    }
    in_len = 80000;
        while (in_len > 0 && !feof(f)) {
        len = av_parser_parse2(parser, c, &avpkt.data, &avpkt.size, arghwtf, in_len,
                                   pts, dts, AV_NOPTS_VALUE);

            len2 = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
            if (len2 < 0) {
                fprintf(stderr, "Error while decoding frame %d\n", frame);
                exit(1);
            }
            if (got_picture) {
        if(!screen) {
            video_open(c, filename);

            rect.x = 0;
            rect.y = 0;
            rect.w = c->width;
            rect.h = c->height;
            inv_fps = av_q2d(c->time_base);
            fprintf(stderr, "w:%i h:%i\n", rect.w, rect.h);

            luma = malloc(c->width*c->height);
            chroma = malloc(c->width*c->height/4);

            SDL_DisplayYUVOverlay(yuv_overlay, &rect);

            signal(SIGINT, sigint_handler);
        }
                fprintf(stderr, "\rDisplaying %c:frame %3d (%02d:%02d)...", av_get_pict_type_char(picture->pict_type), frame, frame/1440, (frame/24)%60);
                fflush(stderr);

        SDL_LockYUVOverlay(yuv_overlay);

                for(i=0;i<c->height;i++) {
                  memcpy(luma + i * c->width, picture->data[0] + i * picture->linesize[0], c->width);
                }
        memcpy(yuv_overlay->pixels[0], luma, c->width * c->height);
                for(i=0;i<c->height/2;i++) {
                  memcpy(chroma + i * c->width/2, picture->data[2] + i * picture->linesize[2], c->width/2);
                }
        memcpy(yuv_overlay->pixels[1], chroma, c->width * c->height / 4);
                for(i=0;i<c->height/2;i++) {
                  memcpy(chroma + i * c->width/2, picture->data[1] + i * picture->linesize[1], c->width/2);
                }
        memcpy(yuv_overlay->pixels[2], chroma, c->width * c->height / 4);

        SDL_UnlockYUVOverlay(yuv_overlay);
        SDL_DisplayYUVOverlay(yuv_overlay, &rect);

        while(get_time_diff(t) < inv_fps) {
            sleep(1000);
        }
                frame++;
        gettimeofday(&t, 0);
            }
        memcpy(arghwtf, arghwtf + len, 80000-len);
        fread(arghwtf + 80000 - len, 1, len, f);
        }

    /* some codecs, such as MPEG, transmit the I and P frame with a
       latency of one frame. You must do the following to have a
       chance to get the last frame of the video */
    avpkt.data = NULL;
    avpkt.size = 0;
    len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
    if (got_picture) {
        printf("saving last frame %3d\n", frame);
        fflush(stdout);

    /* Display last frame here, same code as in the decoding loop above. */

        frame++;
    }

    fclose(f);

    avcodec_close(c);
    av_free(c);
    av_free(picture);
    printf("\n");
}

它给出了错误:

||=== H264_decoding, Debug ===|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp||In function ‘int main(int, char**)’:|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|107|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|136|warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h:3629) [-Wdeprecated-declarations]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|136|warning: ‘AVFrame* avcodec_alloc_frame()’ is deprecated (declared at /home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h:3629) [-Wdeprecated-declarations]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|138|error: invalid conversion from ‘int’ to ‘AVDiscard’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|140|error: ‘avcodec_open’ was not declared in this scope|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|163|error: invalid conversion from ‘char*’ to ‘const uint8_t* {aka const unsigned char*}’ [-fpermissive]|
/home/yoohoo/ffmpeg_build/include/libavcodec/avcodec.h|4465|error:   initializing argument 5 of ‘int av_parser_parse2(AVCodecParserContext*, AVCodecContext*, uint8_t**, int*, const uint8_t*, int, int64_t, int64_t, int64_t)’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|181|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|182|error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|188|error: ‘av_get_pict_type_char’ was not declared in this scope|
/home/yoohoo/codeblocks/Real-time video streaming/H264_decoding/main.cpp|210|error: ‘sleep’ was not declared in this scope|
||=== Build finished: 9 errors, 2 warnings ===|

我想知道这是一个不兼容的问题，因为我将这个 C 程序移到了 C++，但我最终需要在 C++ 中使用它。如何解决这些无效转换问题？提前致谢!

Answer 1

在代码的 main() 函数中

  char *arghwtf = malloc(INBUF_SIZE);

您已经使用返回 void * 的 malloc 函数分配了内存，并且您正在将此 void * 分配给 char *，这就是您收到错误的原因。您必须将其类型转换为 char *。

试试这个。

 char *arghwtf =(char *) malloc(INBUF_SIZE);