i take a look at your config file but i haven't see the exact package which conntains codecs.
;; This is an operating system configuration template
(use-modules (gnu)
(gnu system nss)
(gnu services databases))
(use-service-modules desktop)
(use-package-modules certs gnome)
(operating-system
(host-name "guixSd")
(timezone "Europe/Paris")
(locale "en_US.utf8")
(bootloader (bootloader-configuration
(bootloader grub-bootloader)
(target "/dev/sda")))
(file-systems (cons (file-system
(device (file-system-label "my-root"))
(mount-point "/")
(type "ext4"))
%base-file-systems))
(users (cons (user-account
(name "guy")
(comment "brother")
(group "users")
(supplementary-groups '("wheel" "netdev"
"audio" "video"))
(home-directory "/home/guy"))
%base-user-accounts))
;; This is where we specify system-wide packages.
(packages (cons* nss-certs ;for HTTPS access
gvfs ;for user mounts
%base-packages))
(services (cons* (gnome-desktop-service)
(service mysql-service-type)
%desktop-services))
;; Allow resolution of '.local' host names with mDNS.
(name-service-switch %mdns-host-lookup-nss))
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