what is 'linesize alignment' meaning?

Question

I\'m following ffmpeg tutorial in http://dranger.com/ffmpeg/tutorial01.html.

I have just found that avpicture_get_size function is deprecated.

So I

Answer 1

My practice：

1.avpicture deprecated problem, I replace avpicture functions with AVFrame & imgutils functions. code sample:

   //AVPicture           _picture;
   AVFrame             *_pictureFrame;
   uint8_t             *_pictureFrameData;

...

//_pictureValid = avpicture_alloc(&_picture,
//                                AV_PIX_FMT_RGB24,
//                               _videoCodecCtx->width,
//                               _videoCodecCtx->height) == 0;

_pictureFrame = av_frame_alloc();
_pictureFrame->width = _videoCodecCtx->width;
_pictureFrame->height = _videoCodecCtx->height;
_pictureFrame->format = AV_PIX_FMT_RGB24;

int size = av_image_get_buffer_size(_pictureFrame->format,
                                    _pictureFrame->width,
                                    _pictureFrame->height,
                                    1);

//dont forget to free _pictureFrameData at last                                    
_pictureFrameData = (uint8_t*)av_malloc(size);

 av_image_fill_arrays(_pictureFrame->data,
                      _pictureFrame->linesize,
                      _pictureFrameData,
                      _pictureFrame->format,
                      _pictureFrame->width,
                      _pictureFrame->height,
                      1);

...

if (_pictureFrame) {
    av_free(_pictureFrame);
    if (_pictureFrameData) {
        free(_pictureFrameData);
    }
}

2.align parameter

first I set align to 32, but for some video streams it did not work, cause distorted images. Then I set it to 16(my environment : mac, Xcode, iPhone6), the some streams works well. But at last i set align to 1, for I have found this

Fill in the AVPicture fields, always assume a linesize alignment of 1.