I just tested it out, here's your issue: You should be using ecm-uncompress
How I found the issue:
dpkg -L [PACKAGE NAME]
shows all files that were installed by a certain package. In this case, with dpkg -L ecm
it shows:
/.
/usr
/usr/bin
/usr/bin/ecm-compress
/usr/share
/usr/share/doc
/usr/share/doc/ecm
/usr/share/doc/ecm/changelog.Debian.gz
/usr/share/doc/ecm/copyright
/usr/share/man
/usr/share/man/fr
/usr/share/man/fr/man1
/usr/share/man/fr/man1/ecm-uncompress.1.gz
/usr/share/man/fr/man1/ecm-compress.1.gz
/usr/share/man/man1
/usr/share/man/man1/ecm-uncompress.1.gz
/usr/share/man/man1/ecm-compress.1.gz
/usr/bin/ecm-uncompress
Chiefly of note there are the ones in the /usr/bin
directory:
/usr/bin
/usr/bin/ecm-compress
/usr/bin/ecm-uncompress
These are the only 'commands' that were installed by the package (aside from man ecm-uncompress ecm-compress