FFmpeg:Jpeg 文件到 AVFrame [英] FFmpeg: Jpeg file to AVFrame

问题描述

我需要使用 FFmpeg 库将几个 jpg 文件加入视频中.但是我在阅读这些文件时遇到了问题.这是一个读取图像文件并制作 AVFrame 的函数:

I need to join several jpg files into video using FFmpeg library. But I have a problem with reading this files. Here is a function which reads image file and makes AVFrame:

AVFrame* OpenImage(const char* imageFileName)
{
    AVFormatContext *pFormatCtx;

    if(av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL)!=0)
    {
        printf("Can't open image file '%s'
", imageFileName);
        return NULL;
    }       

    dump_format(pFormatCtx, 0, imageFileName, false);

    AVCodecContext *pCodecCtx;

    pCodecCtx = pFormatCtx->streams[0]->codec;
    pCodecCtx->width = W_VIDEO;
    pCodecCtx->height = H_VIDEO;
    pCodecCtx->pix_fmt = PIX_FMT_YUV420P;

    // Find the decoder for the video stream
    AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if (!pCodec)
    {
        printf("Codec not found
");
        return NULL;
    }

    // Open codec
    if(avcodec_open(pCodecCtx, pCodec)<0)
    {
        printf("Could not open codec
");
        return NULL;
    }

    // 
    AVFrame *pFrame;

    pFrame = avcodec_alloc_frame();

    if (!pFrame)
    {
        printf("Can't allocate memory for AVFrame
");
        return NULL;
    }

    int frameFinished;
    int numBytes;

    // Determine required buffer size and allocate buffer
    numBytes = avpicture_get_size(PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);
    uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));

    avpicture_fill((AVPicture *) pFrame, buffer, PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);

    // Read frame

    AVPacket packet;

    int framesNumber = 0;
    while (av_read_frame(pFormatCtx, &packet) >= 0)
    {
        if(packet.stream_index != 0)
            continue;

        int ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
        if (ret > 0)
        {
            printf("Frame is decoded, size %d
", ret);
            pFrame->quality = 4;
            return pFrame;
        }
        else
            printf("Error [%d] while decoding frame: %s
", ret, strerror(AVERROR(ret)));
    }
}

这不会导致错误，但只会创建黑框，没有图像.怎么了?

This causes no error but creates only black frame, no image. What is wrong?

推荐答案

这段代码是正确的(除了配色问题).向视频添加帧时出现错误.

This code is correct (except of problem with color scheme). There was a bug in adding frame to video.

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