Engine Library Database: Album Art Hash

Engine DJ Software Engine DJ (Mac & PC)
3

Thank you for the tag @MrWilks <3. This is something i’ve honestly been meaning to look into.

Short answer

I don’t know how they calculate the SHA1 and I can verify your findings. A simple sha1sum <image.png|jpg|whatever> doesn’t produce the same value as what’s in AlbumArt.hash.

Long Answer

  • Images are all stored in raw PNG format in AlbumArt.albumArt
  • All album art are all scaled to (max) 256x256 pixels
  • Images may be salted or the SHA1 may be calculated somewhere in the pipeline from extracting the source image from the audio metadata before it’s stored in the DB

image
image1704×1140 271 KB

Using exiftool and ffmpeg, one can extract images from files:

ffmpeg -hide_banner -loglevel error -y -i INPUT_FILE_HERE -an -vcodec copy OUTPUT_FILE_HERE

or

 exiftool -Picture INPUT_FILE_HERE  -b  > OUTPUT_FILE_HERE

Running sha1 against both tools nets the same result, telling me that the extract works well. I also added the extract of a target album art image directly from the database blob and even tried to use ffmpeg to resize the image to a png file and got different results. (i’m not sure what PNG settings are used to resize fwiw).

user@CommanderKeen:x$ sha1sum from*
439d586667e14887f730cd34b2cd7fde6cdc2189  from-db.png
319454523f3d77b2aebf4d9ba543c64ee0fa9c0a  from-exiftool.jpg
319454523f3d77b2aebf4d9ba543c64ee0fa9c0a  from-ffmpeg.jpg
96aef873f12e55447650d700f65437b37bdd34de  from-ffmpeg.png

@DeathCamel57 , one thing to think about is that Engine OS likely does not care about the how the SHA1 is calculated, but Engine DJ does, because it’s responsible for importing data. So… your tool likely can do what it wants to do and just use the raw SHA1 value from the extracted image of a song and put that in the table. Worse case scenario, a database has a some duplicate image records. Doesn’t seem to be a huge deal for most users with small collections.

If you do come up with the answer, please share =)

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