The Amlogic S905X is an advanced application processor designed for OTT/IP Set Top Box (STB) and high-end media box applications. It integrates a powerful CPU/GPU subsystem, a secured 4K video CODEC engine and HDR image processing pipeline..

The main system CPU is a quad-core ARM Cortex-A53 CPU with L1 instruction/data cache for each core and a large unified L2 cache to improve system performance. In addition, the Cortex-A53 CPU includes the NEON SIMD co-processor to improve software media processing capability. The quad-core ARM Cortex-A53 CPU can be overdriven to 2GHz and has a wide bus connecting to the memory sub-system.

The graphic subsystem consists of two graphic engines and a flexible video/graphic output pipeline. The five core ARM Mali-450 GPU including dual geometry processors (GP) and triple pixel processors (PP).The multi-core GPU processor handles all OpenGL ES 1.1/2.0 and OpenVG graphics programs, while the 2.5D graphics processor handles additional scaling, alpha, rotation and color space conversion operations. Together, the CPU and GPU handle all operating system, networking, user-interface and gaming related tasks. The video output pipeline includes advanced HDR10 and HLG HDR processing, REC709/BT2020 processing, motion adaptive edge enhancing de-interlacing, flexible programmable scalar, and many picture enhancement filters before passing the enhanced image to the video output ports.

Amlogic Video Engine (AVE-10) offloads the Cortex-A53 CPUs from all video CODEC processing. It includes dedicated hardware video decoder and encoder. AVE-10 is capable of decoding 4Kx2K resolution video at 60fps with complete Trusted Video Path (TVP) for secure applications and supports full formats including MVC, MPEG-1/2/4, VC-1/WMV, AVS, AVS+, RealVideo, MJPEG streams, H.264, H265-10, VP9-10 and also JPEG pictures with no size limitation. The independent encoder is able to encode in JPEG or H.264 up to 1080p at 60fps.

The chipset  integrates all standard audio/video input/output interfaces including a HDMI2.0a transmitter with 3D, HDR, CEC and HDCP 2.2 support, stereo audio DAC, a CVBS output, PCM, I2S and SPDIF digital audio input/output interfaces, and a stereo PDM digital MIC inputs.

The processor has rich network and peripheral interfaces, including a 10/100M Ethernet MAC with FE PHY interface, dual USB 2.0 high-speed ports (one OTG and one HOST) and multiple SDIO/SD card controllers, UART, I2C, high-speed SPI and PWMs. Standard development environment utilizing GNU/GCC Android tool chain is supported.

The greatest spotlight of the S905X is that it supports VP9 decoding while the S905 does not. Both of them support H.265 Another one is the price. As a newer model, S905X has better performance, however, the price is same or a little lower. Last,  S905X is tailored to Android 6.0, while S905 is for Android 5.1: