如何将来自摄像机的输入图像编码为H.264流？

Question

我试图使用Mac OS X 10.9.5上的libx264实时将来自MacBook Pro内置FaceTime高清摄像头的输入图像实时编码为H.264视频流。

下面是我所采取的步骤：在15fps的使用AVFoundation API（AVCaptureDevice类等）

使用libswscale将图像转换成看见320×180 YUV420P格式

1. 获取1280×720从相机32BGRA图像。
2. 使用libx264将图像编码为H.264视频流（基线配置文件）。

我每次从相机获取图像时都会应用上述步骤，相信编码器会跟踪编码状态并在可用时生成NAL单元。因为我希望在向编码器提供输入图像的同时获得编码帧，所以我决定每隔30帧（2秒）刷新一次编码器（调用x264_encoder_delayed_frames（））以调用x264_encoder_delayed_frames（）。但是，当我重新启动编码时，编码器会在一段时间后停止（x264_encoder_encode（）永不返回）。我尝试在刷新之前更改帧数，但情况没有改变。

下面是相关的代码（我省略了图像捕捉代码，因为它看起来没有问题。）

你能指出什么我可能是做错了？

x264_t *encoder; 
x264_param_t param; 

// Will be called only first time. 
int initEncoder() { 
    int ret; 

    if ((ret = x264_param_default_preset(&param, "medium", NULL)) < 0) { 
    return ret; 
    } 

    param.i_csp = X264_CSP_I420; 
    param.i_width = 320; 
    param.i_height = 180; 
    param.b_vfr_input = 0; 
    param.b_repeat_headers = 1; 
    param.b_annexb = 1; 

    if ((ret = x264_param_apply_profile(&param, "baseline")) < 0) { 
    return ret; 
    } 

    encoder = x264_encoder_open(&param); 
    if (!encoder) { 
    return AVERROR_UNKNOWN; 
    } 

    return 0; 
} 

// Will be called from encodeFrame() defined below. 
int convertImage(const enum AVPixelFormat srcFmt, const int srcW, const int srcH, const uint8_t *srcData, const enum AVPixelFormat dstFmt, const int dstW, const int dstH, x264_image_t *dstData) { 
    struct SwsContext *sws_ctx; 
    int ret; 
    int src_linesize[4]; 
    uint8_t *src_data[4]; 

    sws_ctx = sws_getContext(srcW, srcH, srcFmt, 
         dstW, dstH, dstFmt, 
         SWS_BILINEAR, NULL, NULL, NULL); 

    if (!sws_ctx) { 
    return AVERROR_UNKNOWN; 
    } 

    if ((ret = av_image_fill_linesizes(src_linesize, srcFmt, srcW)) < 0) { 
    sws_freeContext(sws_ctx); 
    return ret; 
    } 

    if ((ret = av_image_fill_pointers(src_data, srcFmt, srcH, (uint8_t *) srcData, src_linesize)) < 0) { 
    sws_freeContext(sws_ctx); 
    return ret; 
    } 

    sws_scale(sws_ctx, (const uint8_t * const*)src_data, src_linesize, 0, srcH, dstData->plane, dstData->i_stride); 
    sws_freeContext(sws_ctx); 
    return 0; 
} 

// Will be called for each frame. 
int encodeFrame(const uint8_t *data, const int width, const int height) { 
    int ret; 
    x264_picture_t pic; 
    x264_picture_t pic_out; 
    x264_nal_t *nal; 
    int i_nal; 

    if ((ret = x264_picture_alloc(&pic, param.i_csp, param.i_width, param.i_height)) < 0) { 
    return ret; 
    } 

    if ((ret = convertImage(AV_PIX_FMT_RGB32, width, height, data, AV_PIX_FMT_YUV420P, 320, 180, &pic.img)) < 0) { 
    x264_picture_clean(&pic); 
    return ret; 
    } 

    if ((ret = x264_encoder_encode(encoder, &nal, &i_nal, &pic, &pic_out)) < 0) { 
    x264_picture_clean(&pic); 
    return ret; 
    } 

    if(ret) { 
    for (int i = 0; i < i_nal; i++) { 
     printNAL(nal + i); 
    } 
    } 

    x264_picture_clean(&pic); 
    return 0; 
} 

// Will be called every 30 frames. 
int flushEncoder() { 
    int ret; 
    x264_nal_t *nal; 
    int i_nal; 
    x264_picture_t pic_out; 

    /* Flush delayed frames */ 
    while (x264_encoder_delayed_frames(encoder)) { 
    if ((ret = x264_encoder_encode(encoder, &nal, &i_nal, NULL, &pic_out)) < 0) { 
     return ret; 
    } 

    if (ret) { 
     for (int j = 0; j < i_nal; j++) { 
     printNAL(nal + j); 
     } 
    } 
    } 
} 

Answer 1

当不存在更多输入帧时，即在编码结束时，您不应该在每帧之后刷新延迟帧，而只能刷新一次。