Decoding mJPEG with libavcodec

Question

I am creating video conference application. I have discovered that webcams (at least 3 I have) provide higher resolutions and framerates for mJPEG output format. So far I was us

Answer 1

After suggestions from comments, I came up with working solution.

Initialization:

av_init_packet(&_inputPacket);

AVCodec * codecDecode = avcodec_find_decoder(AV_CODEC_ID_MJPEG);

_transcoder = avcodec_alloc_context3(codecDecode);
avcodec_get_context_defaults3(_transcoder, codecDecode);
avcodec_open2(_transcoder, codecDecode, nullptr);

// swscale contex init
mJPEGconvertCtx = sws_getContext(width, height, AV_PIX_FMT_YUVJ422P, 
        width, height, AV_PIX_FMT_YUV420P, SWS_FAST_BILINEAR, nullptr, nullptr, nullptr);

// x264 pic init
x264_picture_t _pic_in;
x264_picture_alloc(&_pic_in, X264_CSP_I420, width, height);
_pic_in.img.i_csp = X264_CSP_I420 ;
_pic_in.img.i_plane = 3;
_pic_in.img.i_stride[0] = width;
_pic_in.img.i_stride[1] = width / 2;
_pic_in.img.i_stride[2] = width / 2;

_pic_in.i_type = X264_TYPE_AUTO ;
_pic_in.i_qpplus1 = 0;

Transcoding:

_inputPacket.size = size;
_inputPacket.data = data;

int got_picture;

// decode
avcodec_decode_video2(_transcoder, _outputFrame, &got_picture, &_inputPacket); 

// transform
sws_scale(_mJPEGconvertCtx, _outputFrame->data, _outputFrame->linesize, 0, height, 
        _pic_in.img.plane, _pic_in.img.i_stride);

Afterwards, _pic_in is used directly by x264. Image is fine, but the transcoding times are horrible for higher resolutions.