Video Writer always uses YUV420P to write raw videos (Bug #782)

When I am trying to add images to an uncompressed AVI file, the VideoWriter always uses the YUV420P+H263 format. However my intention is to generate the Gray8+Raw format.

Later I figured out the problem that the switch (codec_id) goes to the default "PIX_FMT_YUV420P". Please refer to the following code.

/********* cap_ffmpeg.cpp @ line 1267 ***/
case CODEC_ID_RAWVIDEO:
default:
// good for lossy formats, MPEG, etc.
codec_pix_fmt = PIX_FMT_YUV420P;
break;
/**********************************************/

It works fine, when I change the code as below.

/************* cap_ffmpeg.cpp *******/
case CODEC_ID_RAWVIDEO:
codec_pix_fmt = input_pix_fmt;
break;
default:
// good for lossy formats, MPEG, etc.
codec_pix_fmt = PIX_FMT_YUV420P;
break;
/*******************************************/