🛠 Serveur multimédia HDMI avec le GPU VideoCore IV

Objectives

Transform the Raspberry Pi 3 A+ into a living room media player: 1080p30 video hardware-decoded by the VideoCore IV GPU (H.264 and MPEG-4, 1080p30 decoding and encoding, OpenGL ES 1.1/2.0), full-size HDMI output — plus composite video via the 4-pole jack for older TVs. All over WiFi, without Ethernet.

Hardware

• Raspberry Pi 3 A+, 5 V/2.5 A power supply, TV via HDMI (or composite jack)
• microSD ≥ 16 GB; video streams via WiFi from a network share
• 512 MB of RAM shared between CPU/GPU: gpu_mem tuning is essential
• "Appliance" alternative: dedicated LibreELEC image for Kodi

Full code

# 1) Allouer la mémoire GPU (128 Mo suffisent pour du 1080p ; au-delà,
#    l'OS n'a plus que 384 Mo sur les 512 Mo partagés)
echo 'gpu_mem=128' | sudo tee -a /boot/firmware/config.txt

# 2) Lecteur avec décodage matériel H.264
sudo apt install -y omxplayer mpv
omxplayer --horizon 0 video_1080p.mp4          # décodage GPU VideoCore
mpv --hwdec=mmal video_1080p.mp4               # ou lecture via Kodi/mpv

# 3) Montage du NAS en WiFi (seul réseau de la carte)
sudo mkdir -p /mnt/nas && sudo mount -t nfs nas:/videos /mnt/nas

# 4) Sortie composite (téléviseur cathodique) : ajouter au config.txt
#    sdtv_mode=pal  puis redémarrer ; l'HDMI reste disponible.
sudo reboot

Expected verification

omxplayer plays a 1080p30 H.264 file smoothly while watch vcgencmd get_throttled remains at 0x0; the CPU (4× A53) stays below 40% thanks to GPU decoding. Audio outputs via the 4-pole jack or HDMI depending on the setting.

Common errors

• Running a browser + Kodi simultaneously: with 512 MB of RAM, the OS saturates quickly (swap/OOM) — choose a single use case, or use LibreELEC.
• gpu_mem=256 copied from a Pi 4 tutorial: the OS no longer has enough RAM on this board; stick to 96–128 MB.
• Expecting 4K/H.265: the VideoCore IV only decodes H.264/MPEG-4 at 1080p30; HEVC would have to be decoded by the CPUs, to no avail.
• Choppy network streams: WiFi 802.11ac is good but finicky behind furniture — move the router closer rather than increasing power.
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