On Tue, 2010-11-16 at 12:28 +0000, Mark Kenna wrote:
> 
> On 16/11/2010 12:24, sq.cheng wrote:
> > use the video decode to do it
> > just like decoding mpeg4 or h.264, with the JPEG codec id(I don't remember
> > what's name, something like MJPEG)
> > then decode one frame, it will output one yuv frame,
> > and it seems I once met the output is yuyv, according to the input image.
> >
> >
> > On Tue, Nov 16, 2010 at 8:11 PM, Mark Kenna<
> > [email protected]>  wrote:
> >
> >> Hi Guys
> >>
> >> Does anyone know if it's possible to convert a JPEG to YUV frame simply
> >> using LibAv*? Currently I am converting to a Bitmap and converting the RGB
> >> data to a YUV frame using sws. If there is a simpler (and more efficient)
> >> method I would love to know about it.
> >>
> >> Thanks,
> >> Mark.
> >>
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> >>
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> Interesting - I will give it a try. If someone could specify the exact 
> codec to use I would appreciate it.
> 
> Thanks,
> Mark.

Use the mjpeg decoder (CODEC_ID_MJPEG). It should work fine.

Also, since jpeg supports a number of YUV formats you might want to make
sure your input is in the format you want. Otherwise you will have to
use libswscale anyway. It's probably quite a bit faster converting YUV
-> YUV than RGB -> YUV though.

/Tomas

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