Data Set Overview
      =================

      This data set contains products acquired by the MAHLI
      instrument. 

      This data set uses the Committee on Data Management
      and Computation (CODMAC) data level numbering system.
      The MSL MAHLI EDRs are considered Level 2 or Edited
      Data (equivalent to NASA Level 0). The EDRs are
      reconstructed from Level 1 or Raw Data.


      Processing
      ==========

      After receipt on Earth, processing at JPL begins
      with the reconstruction of packetized telemetry data
      (raw telemetry packet SFDU's with CFDP headers) into
      depacketized binary data products and associated Earth
      metadata files. MMMEDRGEN combines the Earth metadata
      with additional data extracted from the binary data files
      to create an EDR with the corresponding label.  (SFDU -
      Standard Formatted Data Unit; CCSDS - Consultative
      Committee for Space Data Systems; CFDP - CCSDS File
      Delivery Protocol)


      Data
      ==== 

      The EDRs produced contain raw, uncalibrated data
      and have detached PDS-compliant labels. The Mast Camera
      (Mastcam), Mars Hand Lens Imager (MAHLI), and Mars Descent
      Imager (MARDI) Experiment Data Record (EDR) and Reduced Data
      Record (RDR) PDS Data Products Software Interface Specification
      contains a detailed description of the EDR formatted products.

      There are 8 video data types (5 images, 3 thumbnails) that can
      be wrapped into the original data format that is transferred
      from the cameras. Some of these are compressed in a format
      which can reproduce an image identical to the original image
      on the instrument (lossless compression), some are transferred
      in lossy format, some are full-scale and others sub-sampled
      (the only sub-sampled is by a factor of 8, used to produce
      thumbnail images). The EDR data file includes the camera
      mini-header generated by the camera, followed by original
      image data as formatted by the camera.

      Not including sub-framing, MAHLI can take a variety of
      image data formats and accomplish this by internal processing.
      The cameras always acquire raw 12-bit data. Normally, the
      12-bit raw data are converted from 12-to-8-bits through the
      use of a variety of companding (compress/expand) lookup tables,
      the most generally used being a modified square-root encoding
      scheme that allocates additional values to low DNs. These
      companded, 8-bit images can then be processed either immediately,
      and stored into each camera's 8-Gbyte buffer, or they can be
      stored unprocessed in the buffer, and then later processed in
      response to downlink commands. It is this flexibility that leads
      to the complexities of the raw data format and its description.

      In addition to the 12-to-8-bit companding, on-board processing
      includes the following capabilities: Bayer pattern
      interpolation, lossless compression, and JPEG compression.
      Except for thumbnails, the cameras do not support sub-sampling
      or resampling, but do support sub-framing.

      Thumbnails are produced by creating a scratch JPEG image, and
      extracting the lowest order coefficients of the discrete cosine
      transform 8x8 pixel compression block, or minimum compression
      unit (MCU), which is essentially the average of the 8x8 spatial
      domain MCU. These coefficients are then assembled into a smaller
      image which is then JPEG compressed.  The extraction of these
      coefficients is the only way MAHLI images are ever sub-sampled.

      The following is a table of the different video product types
      generated by MAHLI which are contained within the raw camera
      data record.
 
      Type  Product     Format      Pixel bits
      -------------------------------------------
      J     Video       Raster       8
      K     Video       Lossless     8
      L     Video       JPEG gray    8
      M     Video       JPEG 422    24
      N     Video       JPEG 444    24
      O     Thumbnail   Raster       8
      P     Thumbnail   JPEG gray    8
      Q     Thumbnail   JPEG 444    24


      Refer to the Mast Camera (Mastcam), Mars Hand Lens Imager (MAHLI),
      and Mars Descent Imager (MARDI) Experiment Data Record (EDR)
      and Reduced Data Record (RDR) PDS Data Products Software
      Interface Specification for further details on the MAHLI data
      products.

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