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Hi~. I'm testing ipp7.0 sample code for jpeg decoding.
An interest thing is there is no defintion about YUV420 format(not pixel but planar).
The supported sampling formats are
JS_444, JS_422, JS_244, JS_411, JS_OTHER.
In addition, I think the function, JERRCODE CJPEGDecoder::DetectSampling(void) function in jpegdec.cpp file is used for acquring sampling format.
By the way, inside the function,
case 3:
if(m_ccomp[0].m_hsampling == 1 && m_ccomp[0].m_vsampling == 1 &&
m_ccomp[1].m_hsampling == 1 && m_ccomp[1].m_vsampling == 1 &&
m_ccomp[2].m_hsampling == 1 && m_ccomp[2].m_vsampling == 1)
{
m_jpeg_sampling = JS_444;
}
else if(m_ccomp[0].m_hsampling == 2 && m_ccomp[0].m_vsampling == 1 &&
m_ccomp[1].m_hsampling == 1 && m_ccomp[1].m_vsampling == 1 &&
m_ccomp[2].m_hsampling == 1 && m_ccomp[2].m_vsampling == 1)
{
m_jpeg_sampling = JS_422; <=== Is this correct? YUV420 is also the same hsampling and vsampling value if the function search the sampling like this. Isn't it?
}
If I am wrong, please forgive my ignorance. Anyway I would like to know how to decode YUV420 encoded jpeg image without using additional converting such as YUV422toYUV420....with ipp.
Many thanks ahead.
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UIC JPEG use 411 sampling name to refer to actually 420 sampling factors (that is by historic reasons). In other words, in UIC caseJS_411point to horizontal sampling 2:1 and vertical sampling 2:1 which is what other call as 420.
Regards,
Vladimir
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