On 9 September 2010 08:30, Naveed Gazi <[email protected]> wrote:
> Hi all,
>
> I'm new to using the libavcodec library and am currently running into some
> issues trying to decode a M-JPEG stream that I collect from a webcam. I
> check the avContext->pix_fmt both before and after I call
>
> avcodec_decode_video2(avContext, decPict, &gotPic, &avpkt)
>
> to determine what the pixel format is before/after decoding. Prior to
> decoding pix_fmt = -1 (i.e. PIX_FMT_NONE) and after decoding pix_fmt = 13
> (i.e. PIX_FMT_YUVJ422P).
>
> I am not sure how to deal with YUVJ422P. My video player is currently
> capable of working with YUV420P and I have to make it capable of handling
> YUVJ422P as well. So far I didn't find any information on how the Y,U and V
> arrays are organized in YUVJ422P or any other relevant information about how
> this format works (google did not help). I was hoping someone could help me
> determine how to either convert YUVJ422P to YUV420P or explain how YUVJ422P
> works or point me to some good resources. Your help is much appreciated and
> thanks in advance.
>

YUVJ indicates the scaling used by the JPEG algorithm, which uses the
full [0, 255] range rather than the typical [16, 235].

As Mark mentioned, just use sws_scaler for the conversion.

Josh
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