[Bug 1809014] [NEW] mpeg-2 detected as tga (Targa image)

[Finn Kempers]

Public bug reported:

It appears that currently using either the file command or through the
File::LibMagic interface that 1:5.34-2 on Cosmic (18.10) makes a MPEG-2
file be detected as Targa at a higher priority, thus taking precedence
over being what it actually is. See the below lines as examples using
clips from http://hubblesource.stsci.edu/sources/video/clips/ as
examples:

$ file -k /home/piratefinn/Downloads/hst_2.mpg 
/home/piratefinn/Downloads/hst_2.mpg: Targa image data - Map 63635 x 65536 x 1 +268 +60928 - 11-bit alpha - top - right - four way interleave MPEG sequence, v2, program multiplex (Lepton 3.x), scale 0-0, spot sensor temperature 0.000000, unit celsius, color scheme 0, calibration: offset 0.000000, slope 0.000000\012- data

Note that this appears to only affect MPEG-2 (and possibly higher) as
MPEG-1 is detected corretly.

$ file -k /home/piratefinn/Downloads/hst_1.mpg 
/home/piratefinn/Downloads/hst_1.mpg: MPEG sequence, v1, progressive Y'CbCr 4:2:0 video, 320x240, 4:3, 29.97 fps (Lepton 2.x), scale 1-2, spot sensor temperature 0.000000, unit celsius, color scheme 0, show spot sensor, show scale bar, maximum point enabled, calibration: offset 586.228088, slope -411899156202779801569722368.000000\012- data
file -k /home/piratefinn/Downloads/hst_1.mpg

This appears to not be an issue in 1:5.25 used in 16.04, however looking
through the github it appears since then in possible 5.26 (or above)
changes as seen in
https://github.com/file/file/commit/aee048a020badb5f36008f6d11e7d5b32834bcb2
affected this.

** Affects: file (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1809014

Title:
  mpeg-2 detected as tga (Targa image)

Status in file package in Ubuntu:
  New

Bug description:
  It appears that currently using either the file command or through the
  File::LibMagic interface that 1:5.34-2 on Cosmic (18.10) makes a
  MPEG-2 file be detected as Targa at a higher priority, thus taking
  precedence over being what it actually is. See the below lines as
  examples using clips from
  http://hubblesource.stsci.edu/sources/video/clips/ as examples:

  $ file -k /home/piratefinn/Downloads/hst_2.mpg 
  /home/piratefinn/Downloads/hst_2.mpg: Targa image data - Map 63635 x 65536 x 1 +268 +60928 - 11-bit alpha - top - right - four way interleave MPEG sequence, v2, program multiplex (Lepton 3.x), scale 0-0, spot sensor temperature 0.000000, unit celsius, color scheme 0, calibration: offset 0.000000, slope 0.000000\012- data

  Note that this appears to only affect MPEG-2 (and possibly higher) as
  MPEG-1 is detected corretly.

  $ file -k /home/piratefinn/Downloads/hst_1.mpg 
  /home/piratefinn/Downloads/hst_1.mpg: MPEG sequence, v1, progressive Y'CbCr 4:2:0 video, 320x240, 4:3, 29.97 fps (Lepton 2.x), scale 1-2, spot sensor temperature 0.000000, unit celsius, color scheme 0, show spot sensor, show scale bar, maximum point enabled, calibration: offset 586.228088, slope -411899156202779801569722368.000000\012- data
  file -k /home/piratefinn/Downloads/hst_1.mpg

  This appears to not be an issue in 1:5.25 used in 16.04, however
  looking through the github it appears since then in possible 5.26 (or
  above) changes as seen in
  https://github.com/file/file/commit/aee048a020badb5f36008f6d11e7d5b32834bcb2
  affected this.

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