#18 Errors decoding certain sampling factors

[Calvin Hass]

Originally posted on ImpulseAdventure.com by AllenKK:
(Comment #14146 on 2014/05/21)

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FFMPEG full scale JPEG YUV 422, 444 cannnot be decoded successful but 420 works. You can generate the JPEG file in:

ffmpeg -i my.avi -ss 00:00:10.000 -f image2 -vframes 1 -pix_fmt yuvj422 out.jpg

You can also try this:
https://trac.ffmpeg.org/raw-attachment/ticket/143/yuvj422.jpg

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[Calvin Hass]

I believe the issue involves the use of chroma subsampling factors that have multiple data units per MCU in components other than the first (ie. luminance). This is likely due to a simplification in the way chroma subsampling is expanded in the current code.

Sampling factors from above referenced file:

*** Marker: SOF0 (Baseline DCT) (xFFC0) ***   Number of Img components = 3
        Component[1]: ID=0x01, Samp Fac=0x22 (Subsamp 1 x 1), Quant Tbl Sel=0x00 (Lum: Y)
        Component[2]: ID=0x02, Samp Fac=0x12 (Subsamp 2 x 1), Quant Tbl Sel=0x00 (Chrom: Cb)
        Component[3]: ID=0x03, Samp Fac=0x12 (Subsamp 2 x 1), Quant Tbl Sel=0x00 (Chrom: Cr)

[Calvin Hass]

Chroma subsampling code has now been rewritten in version 1.6.6 and addresses this issue.