JPEG features

The following features are supported for JPEG:

Info

The "info" feature for JPEG is currently empty. It doesn’t export anything.

Quantized DCT coefficients

The "q_dct" feature for JPEG exports the quantized coefficients of the DCT transform that are encoded in the bitstream.

TODO: number:

  • The DC coefficient for this block.

TODO: number:

  • An AC coefficient for this block (from 1 to 63), in the zig-zag scan order.

TODO: (informative) number:

  • The count of vertical blocks per macroblock for each component.

TODO: (informative) number:

  • The count of horizontal blocks per macroblock for each component.

TODO: (informative) number:

  • The index for the Quantization Table for each plane, as defined in the "dqt" feature.

Quantized DCT coefficients (with DC delta)

The "q_dct_delta" feature for JPEG is similar to the "q_dct" feature, but the DC coefficient is expressed as a delta value from the previous DC coefficient.

Note that the previous DC coefficient is not necessarily the one from the block immediately to the left since there might be multiple blocks inside a macroblock, which will be encoded in a raster scan order (left to right, top to bottom) per-macroblock.

TODO: number:

  • The DC coefficient delta for this block.

TODO: number:

  • An AC coefficient for this block (from 1 to 63), in the zig-zag scan order.

TODO: (informative) number:

  • The count of vertical blocks per macroblock for each component.

TODO: (informative) number:

  • The count of horizontal blocks per macroblock for each component.

TODO: (informative) number:

  • The index for the Quantization Table for each plane, as defined in the "dqt" feature.

Quantized DCT coefficients (DC only)

The "q_dc" feature for JPEG is similar to the "q_dct" feature, but only the DC coefficients are available.

TODO: number:

  • The DC coefficient for this block.

TODO: (informative) number:

  • The count of vertical blocks per macroblock for each component.

TODO: (informative) number:

  • The count of horizontal blocks per macroblock for each component.

TODO: (informative) number:

  • The index for the Quantization Table for each plane, as defined in the "dqt" feature.

Quantized DCT coefficients (DC delta only)

The "q_dc_delta" feature for JPEG is similar to the "q_dc" feature, but the DC coefficient is expressed as a delta value from the previous DC coefficient.

TODO: number:

  • The DC coefficient delta for this block.

TODO: (informative) number:

  • The count of vertical blocks per macroblock for each component.

TODO: (informative) number:

  • The count of horizontal blocks per macroblock for each component.

TODO: (informative) number:

  • The index for the Quantization Table for each plane, as defined in the "dqt" feature.

Quantization Table

The "dqt" feature for JPEG exports the quantization tables. These values will be used to multiply the quantized coefficients before they go through the IDCT.

There may be one or multiple tables (for luminance or chrominance planes for example), depending on the encoder.

TODO: number:

  • The quantization value for this index.

Huffman Table

Honestly, you don’t want to mess with this one… You will break the glitched file in incomprehensible ways. I don’t even know why I implemented it… So I won’t even bother explaining it.

TODO: number:

  • The Huffman Table class.

TODO: number:

  • The Huffman Table index.

TODO: number:

  • The Huffman Table value for this amount of bits.