FFMPEG sws_scale在Android上崩溃

Question

我有一个应用程序将图像转换为视频,在Google Play中我看到以下崩溃(我得到的唯一细节是函数的名称,我不理解其余的):

backtrace:
#00 pc 0000cc78 /data/app-lib/com.myapp-1/libswscale.so (sws_scale+204)
#01 pc 000012af /data/app-lib/com.myapp-1/libffmpeg.so (OpenImage+322)

code around pc:
79065c58 e58d8068 e58d2070 e58d3074 059d00b0 

代码指向该功能sws_scale,代码几乎一直在我的设备上工作(Nexus 5)但我看到很多报告,即使是同一个设备也有这个问题.知道为什么会这样吗？

AVFrame* OpenImage(const char* imageFileName, int W_VIDEO, int H_VIDEO, int* numBytes)
{
    AVFormatContext *pFormatCtx;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame;
    int frameFinished;
    uint8_t *buffer;
    AVPacket packet;
    int srcBytes;

    AVFrame* frame2 = NULL;// scaled frame
    uint8_t* frame2_buffer;
    struct SwsContext *resize;

    if(av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL)!=0)
    {
        LOGI("Can't open image file '%s'\n", imageFileName);
        return NULL;
    }
    //dump_format(pFormatCtx, 0, imageFileName, 0);
    if (av_find_stream_info(pFormatCtx) < 0)
    {
        LOGI("Can't find stream info.");
        return NULL;
    }
    pCodecCtx = pFormatCtx->streams[0]->codec;
    pCodecCtx->pix_fmt = PIX_FMT_YUV420P;

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

    // Open codec
    if(avcodec_open(pCodecCtx, pCodec)<0)
    {
        LOGI("Could not open codec\n");
        return NULL;
    }
    pFrame = avcodec_alloc_frame();
    if (!pFrame)
    {
        LOGI("Can't allocate memory for AVFrame\n");
        return NULL;
    }

    // Determine required buffer size and allocate buffer
    srcBytes = avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
    buffer = (uint8_t *) av_malloc(srcBytes * sizeof(uint8_t));
    avpicture_fill((AVPicture *) pFrame, buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);

    // Read frame
    if (av_read_frame(pFormatCtx, &packet) >= 0)
    {
        int ret;
//      if(packet.stream_index != 0)
//          continue;
        ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
        if (ret > 0)
        {
            //LOGI("Frame is decoded, size %d\n", ret);
            pFrame->quality = 4;

            // Create another frame for resized result
            frame2 = avcodec_alloc_frame();
            *numBytes = avpicture_get_size(PIX_FMT_YUV420P, W_VIDEO, H_VIDEO);
            frame2_buffer = (uint8_t *)av_malloc(*numBytes * sizeof(uint8_t));
            avpicture_fill((AVPicture*)frame2, frame2_buffer, PIX_FMT_YUV420P, W_VIDEO, H_VIDEO);

            // Get resize context
            resize = sws_getContext(pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, W_VIDEO, H_VIDEO, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);

            // frame2 should be filled with resized samples
            ret = sws_scale(resize, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, frame2->data, frame2->linesize);
            sws_freeContext(resize);
        }
        else
            LOGI("Error [%d] while decoding frame: %s\n", ret, strerror(AVERROR(ret)));
    }
    av_free(pFrame);
    av_free_packet(&packet);
    avcodec_close(pCodecCtx);
    //av_free(pCodecCtx);
    av_close_input_file(pFormatCtx);
    return frame2;
}

Answer 1

您之后avcodec_decode_video2，仅不检查ret。你也需要检查一下frameFinished。如果frameFinished == 0，则不应使用您的框架（因为未填充）。我不知道图像，但当你解码视频时，这种情况经常发生。您需要读取下一个数据包并提供给 的下一个调用avcodec_decode_video2。

旁注：你为什么要强迫pCodecCtx->pix_fmt = PIX_FMT_YUV420P？它会自动设置为正确的格式av_find_stream_info，您应该将其用作sws_getContext参数。

最后一件事：无需填写您pFrame的avpicture_fill. 您只需要av_frame_alloc()它，并且avcodec_decode_video2会负责填充它。