xenial (1) thumbnailer-admin.1.gz

Provided by: thumbnailer-service_2.4+16.04.20160321-0ubuntu1_amd64 bug

NAME

       thumbnailer-admin - Thumbnailer administrative tool

SYNOPSIS

       thumbnailer-admin command [options]

DESCRIPTION

       The thumbnailer-admin program provides a simple administrative tool to access the thumbnailer-service(1),
       for example, to retrieve a thumbnail, display statistics, or  selectively  clear  one  ore  more  of  the
       service's internal caches.

   Internal caches
       The thumbnailer service maintains three internal caches:

       Image cache
              The  image  cache  stores images that are expensive to retrieve (namely images downloaded from the
              image server (dash.ubuntu.com) or extracted from video files). Images in this cache  are  kept  at
              high resolution, up to a limit of max-thumbnail-size (usually 1920) pixels in the larger dimension
              (see thumbnailer-settings(5)). The image cache is used to create thumbnails at smaller sizes  that
              are  then  inserted  into  the  thumbnail  cache  (to avoid repeated download or extraction of the
              original images).

       Thumbnail cache
              The thumbnail cache stores images that are scaled to a size that was  previously  requested  by  a
              client.  If  a  client  asks for a thumbnail that was previously generated at the same size, it is
              returned from this cache.

       Failure cache
              The failure cache contains the keys for media (local or remote) for which no  thumbnail  could  be
              generated,  either  because a local file does not contain artwork, or because the image server has
              returned an authoritative answer that no image is available.  If a client asks for an  image  that
              is  in  the failure cache, the service does not try to create a thumbnail for some period of time,
              to avoid expensive repeated attempts to retrieve artwork that does not exist.

       Commands that can selectively be applied to these caches use the following cache-id:

       i      Image cache

       t      Thumbnail cache

       f      Failure cache

   Sizes and scaling
       Thumbnails are  never  larger  than  max-thumbnail-size  in  the  larger  dimension  (usually  1920,  see
       thumbnailer-settings(5)), even if a larger size is requested.

       Commands that create thumbnails expect a size in pixels to be specified as follows:

       widthxheight
              Create  a thumbnail scaled to fit a bounding box of width and height, for example, --size 640x480.
              If only a single dimension is provided, the thumbnail is scaled to fit into a square bounding  box
              of the specified size, for example, -s 256.

              Specifying  a  size with one dimension explicitly set to zero leaves that dimension unconstrained.
              For example, --size 0x480 produces a thumbnail no taller than 480 pixels of any width, (subject to
              the max-thumbnail-size limit).

              Specifying   a   size   of  zero  (or  not  specifying  any  size)  is  equivalent  to  specifying
              max-thumbnail-size in both dimensions.

              Scaling always maintains the aspect ratio of the original image, and ensures that a thumbnail  has
              a size of at least one pixel in the smaller dimension.

              Requests  for  thumbnails that are larger than the original image are automatically reduced to the
              original image size, that is, original artwork is never scaled up.

   Media formats and output files
       Most common image formats, such as PNG, JPEG, BMP, and so on, are recognized. For  streaming  media,  the
       recognized formats depend on the installed gstreamer codecs.

       Thumbnails  are  always  returned  in  PNG  format, regardless of the encoding of the original image. The
       generated thumbnail file is tagged with the requested (not actual) image size. For example,

              thumbnailer-admin get --size=320x240 screen.jpg

       creates a file named screen_320x480.png.

COMMAND OVERVIEW

       thumbnailer-admin clear [cache-id]
              Clear all internal caches.

       thumbnailer-admin stats [cache-id]
              Display cache statistics.

       thumbnailer-admin zero-stats [cache-id]
              Zero statistics counters.

       thumbnailer-admin get file [dir]
              Get a thumbnail from a file.

       thumbnailer-admin get-artist artist album [dir]
              Get an artist thumbnail from the image server.

       thumbnailer-admin get-album artist album [dir]
              Get an album thumbnail from the image server.

       thumbnailer-admin compact
              Compact internal caches.

       thumbnailer-admin shutdown
              Shut down the thumbnailer service.

COMMAND REFERENCE

       thumbnailer-admin --help
       thumbnailer-admin -h
              Display a general help message for all commands.

       thumbnailer-admin clear [cache-id]
              Options:
                     --help
                     -h
                            Show help message.

              Clear all three internal caches. If cache-id is provided, clear only the selected cache.

       thumbnailer-admin stats [cache-id]
              Options:
                     --help
                     -h
                            Show help message.
                     --verbose
                     -v
                            Show histogram of entry sizes.

              Display detailed cache statistics. If cache-id is provided, limit  the  display  to  the  selected
              cache.

       thumbnailer-admin zero-stats [cache-id]
              Options:
                     --help
                     -h
                            Show help message.

              Reset  the  statistics  counters  and  timestamps  to  zero.  If  cache-id  is provided, reset the
              statistics only for the selected cache.

       thumbnailer-admin get file [dir]
              Options:
                     --help
                     -h
                            Show help message.
                     --size pixels
                     --s pixels
                            Set the thumbnail size.

              Extract a thumbnail from the specified media file.

              If dir  is  specified,  place  the  thumbnail  into  the  specified  directory  (default:  current
              directory).

              The  output file name is basename_size.png. For example, for a file song.mp3, the output file name
              is song_0x0.png if no specific size was provided.

       thumbnailer-admin get-artist artist album [dir]
              Options:
                     --help
                     -h
                            Show help message.
                     --size pixels
                     --s pixels
                            Set the thumbnail size.

              Retrieve artist artwork for the specified artist and album. The album can be an empty string  but,
              because  artist  names  alone  can  be  ambiguous,  specifying an album as well may yield a better
              result.

              If dir  is  specified,  place  the  thumbnail  into  the  specified  directory  (default:  current
              directory).

              The  output  file name is artist_album_artist_size.png. For example, for Jethro Tull's "Aqualung",
              the file name is Jethro Tull_Aqualung_artist_0x0.png if no specific size was provided.

       thumbnailer-admin get-album artist album [dir]
              Options:
                     --help
                     -h
                            Show help message.
                     --size pixels
                     --s pixels
                            Set the thumbnail size.

              Retrieve album cover artwork for the specified artist and album. The artist can be an empty string
              but,  because album titles alone can be ambiguous, specifying an artist as well may yield a better
              result.

              If dir  is  specified,  place  the  thumbnail  into  the  specified  directory  (default:  current
              directory).

              The  output  file  name is artist_album_album_size.png. For example, for Jethro Tull's "Aqualung",
              the file name is Jethro Tull_Aqualung_album_0x0.png if no specific size was provided.

       thumbnailer-admin compact [cache-id]
              Options:
                     --help
                     -h
                            Show help message.

              Compact all three internal caches so the take up the smallest possible amount of  disk  space.  If
              cache-id is provided, clear only the selected cache.

              After  some  time  of use, the on-disk size of a cache can be 25–30% larger than its nominal size.
              Compaction reclaims the wasted space, but is slow and, while in progress, other thumbnail requests
              are  delayed  until  compaction completes.  (It can take tens of seconds to compact a cache with a
              nominal size of 100 MB, depending on the speed of the hardware.)

       thumbnailer-admin shutdown
              Options:
                     --help
                     -h
                            Show help message.

              Shut down the thumbnailer service. This is useful mainly after changing settings (which  are  read
              only once when the service starts).

SEE ALSO

       thumbnailer-service(1), thumbnailer-settings(5)