JPEG and 411 sampling

JPEG and 411 sampling

Does the IPP jpeg encoder/decoder supports 411 sampling.For instance if I decode a YUV 411 jpeg toYUV 422 nothing happens. The same goes for the encoder when the source is 422 and the destination 411PS: such functionality is missing from the ColorConvert methods if the encoder and decoder.

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Hi,Could you add some more information regarding your question?UIC JPEG enc/dec should support that.You can try uic_transcoder_con sample ("-s" option) to do some experiments.Regards,Sergey

Regards, Sergey

Hi,Basically this is my case:I have created a DLL based on the IPP for encoding and decoding JPEG files. I'm not using the UIC JPEG enc/dec but rather the JPEG end/dec itself (located in the "\ipp-samples\image-codecs\uic\src\codec\image\jpeg"samples folder). For my needs the simple enc/dec is enough - no need to use the whole UIC framework.In most cases everything is working ready well but a coupe of day ago I had the following situation:I try to decode a JPEG with 411 sampling to a YUV 422 buffer and to resulting buffer was empty despite the decoder's functionCJPEGDecoder::ReadData() returning OK.After some debugging I found that theCJPEGDecoder::ColorConvert method was not converting anything. There is only one conversion forYCbCr to YCbCr but for 422 sampling.Basically the same goes for the encoder - no color conversion between 411 source to 422 jpeg.Regards,Martin.

Vladimir  Dudnik's picture

Hi Martin,as it was commented on this forum earlier, IPP JPEG codec do not support resampling 411 <-> 422Compress to JPEG 411 from YUV422JPEG 411 YCbCr to DIB 422 YCbCr?Regards,
Vladimir

HiVladimir,I found this thread but beeing a little old (more that six years old) I decided to ask :)Does Intel have plans to implement such resampling and 420 sampling in the future (considering that six years a very far future) :DRegards,Martin.

Vladimir  Dudnik's picture

Hi Martin,please note that in IJL and later in IPP JPEG implementation sampling name 411 actually mean what most people would call as 420 sampling. Namely, in IPP JPEG 411 sampling does mean that MCU will contain four 8x8 data units (blocks) and Cb/Cr will be presented with only one 8x8 block each. What is literally 420 sampling. IPP keep 411 name by historic reason only.Regards,
Vladimir

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