Question

在我的previous question之后，我找到here的代码，使用C++ avcodec个库在ffmpeg创建视频。

我修改了此代码以符合C++。一切都很好，它会创建mp4个视频。除了输出视频与某些视频管理器一起打开，并且不与其他视频管理器打开。

E.g。我可以通过图腾在Linux上打开它（滑块无论如何都不允许来回）。但是VLC（在同一台Linux机器上）无法打开此文件。可能在Windows中会出现类似的问题。

此代码是否有任何遗漏的过程导致此问题？

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

extern "C" {
    #include <libavcodec/avcodec.h>
    #include <libavutil/opt.h>
    #include <libavutil/imgutils.h>
}

static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,
                   FILE *outfile)
{
    int ret;

    /* send the frame to the encoder */
    if (frame)
        std::cout<<"Send frame "<<(frame->pts)<<std::endl;

    ret = avcodec_send_frame(enc_ctx, frame);
    if (ret < 0) {
        fprintf(stderr, "Error sending a frame for encoding\n");
        exit(1);
    }

    while (ret >= 0) {
        ret = avcodec_receive_packet(enc_ctx, pkt);
        if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
            return;
        else if (ret < 0) {
            fprintf(stderr, "Error during encoding\n");
            exit(1);
        }

        std::cout<<"Write packet "<<(pkt->pts)<<" (size="<<(pkt->size)<<")"<<std::endl;
        // printf("Write packet %3" PRId64" (size=%5d)\n", pkt->pts, pkt->size);
        fwrite(pkt->data, 1, pkt->size, outfile);
        av_packet_unref(pkt);
    }
}

int main(int argc, char **argv)
{
    const char *filename;
    const AVCodec *codec;
    AVCodecContext *c= NULL;
    int i, ret, x, y;
    FILE *f;
    AVFrame *frame;
    AVPacket *pkt;
    uint8_t endcode[] = { 0, 0, 1, 0xb7 };

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
        exit(0);
    }
    filename = argv[1];
    std::string codec_name = "mpeg4";

    avcodec_register_all();

    /* find the mpeg1video encoder */
    codec = avcodec_find_encoder_by_name(codec_name.c_str());
    if (!codec) {
        fprintf(stderr, "Codec '%s' not found\n", codec_name.c_str());
        exit(1);
    }

    c = avcodec_alloc_context3(codec);
    if (!c) {
        fprintf(stderr, "Could not allocate video codec context\n");
        exit(1);
    }

    pkt = av_packet_alloc();
    if (!pkt)
        exit(1);

    /* put sample parameters */
    // c->bit_rate = 400000;
    c->bit_rate = 4000000;
    /* resolution must be a multiple of two */
    // c->width = 352;
    // c->height = 288;
    c->width = 640;
    c->height = 480;
    /* frames per second */
    c->time_base = (AVRational){1, 25};
    c->framerate = (AVRational){25, 1};

    /* emit one intra frame every ten frames
     * check frame pict_type before passing frame
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
    c->gop_size = 10;
    c->max_b_frames = 1;
    c->pix_fmt = AV_PIX_FMT_YUV420P;

    if (codec->id == AV_CODEC_ID_H264)
        av_opt_set(c->priv_data, "preset", "slow", 0);

    /* open it */
    ret = avcodec_open2(c, codec, NULL);
    if (ret < 0) {
        fprintf(stderr, "Could not open codec\n");
        // fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
        exit(1);
    }

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

    frame = av_frame_alloc();
    if (!frame) {
        fprintf(stderr, "Could not allocate video frame\n");
        exit(1);
    }
    frame->format = c->pix_fmt;
    frame->width  = c->width;
    frame->height = c->height;

    ret = av_frame_get_buffer(frame, 32);
    if (ret < 0) {
        fprintf(stderr, "Could not allocate the video frame data\n");
        exit(1);
    }

    /* encode 10 second of video */
    for (i = 0; i < 250; i++) {
        fflush(stdout);

        /* make sure the frame data is writable */
        ret = av_frame_make_writable(frame);
        if (ret < 0)
            exit(1);

        /* prepare a dummy image */
        /* Y */
        for (y = 0; y < c->height; y++) {
            for (x = 0; x < c->width; x++) {
                frame->data[0][y * frame->linesize[0] + x] = uint8_t(x + y + i * 3);
            }
        }

        /* Cb and Cr */
        for (y = 0; y < c->height/2; y++) {
            for (x = 0; x < c->width/2; x++) {
                frame->data[1][y * frame->linesize[1] + x] = uint8_t(128 + y + i * 2);
                frame->data[2][y * frame->linesize[2] + x] = uint8_t(64 + x + i * 5);
            }
        }

        frame->pts = i;

        /* encode the image */
        encode(c, frame, pkt, f);
    }

    /* flush the encoder */
    encode(c, NULL, pkt, f);

    /* add sequence end code to have a real MPEG file */
    fwrite(endcode, 1, sizeof(endcode), f);
    fclose(f);

    avcodec_free_context(&c);
    av_frame_free(&frame);
    av_packet_free(&pkt);

    return 0;
}

构建

g++ -I ./FFmpeg/ video.cpp -L ./fflibs -lavdevice -lavfilter -lavformat -lavcodec -lrt -ldl -lXfixes -lXext -lX11 -lasound -lSDL -lz -lrt -lswresample -lswscale -lavutil -lm -llzma -lbz2 -lswresample -lpthread

运行

./a.out myvideo.mp4

如果通过

转换为bash，此视频就可以了

ffmpeg -i myvideo.mp4 out1.mp4

但我在寻找一种从代码中修复它的方法。

在图腾（Ubuntu）上播放生成的视频：

转化后的视频：

C ++ ffmpeg API创建的视频在某些播放器中无法打开

0 个答案: