A311D的视频路径如下图所示。
其中视频输入包括MIPI CSI和DEMUX，还自带ISP（Image Signal Processor ，图像信号处理器）。CSI是Camera Serial Interface的缩写，用于接摄像头，工作在BT656模式下。Demux用于接外部数字TV tuner和解调器。它可以从TS（MPEG-2 transport stream）/DDR中的输入信号分解成视频信号、音频信号和时钟信号，其中视频信号先被写入DDR，然后由VDEC（video decoder，视频解码器）进行解码。
视频输出主要指VPU（Video Process Unit），包括RDMA（Register Direct Memory Access）、VIU（Video Input Unit）、HDMITX、CVBS（Composite Video Blanking and Sync）和MIPI（Mobile Industry Processor Interface）DSI（Display Serial Interface）等子模块。
VPU是视频处理单元，主要功能就是从Decoder/DDR/HDMIRX等外设接收数据，然后对原数据进行处理以得到高质量的视频画面，最后将这些视频数据通过HDMITX/CVBS/MIPI等外设发送到屏幕。
VIU是视频输入单元，处理像素扫出和基本的色彩空间转换，比如RGB565或RGB888扫出，RGB转换为x/cb/cr等。VIU还包括VPP（Video Post Processing），负责所有从VIU扫出后的后处理，比如混合OSD（On Screen Display）。
Amlogic uses a proprietary lossless image compression protocol and format for their hardware video codec accelerators, either video decoders or video input encoders.
It considerably reduces memory bandwidth while writing and reading frames in memory.
The video decoding IP lies within the DOS memory region, except for the hardware bitstream parser that makes use of an undocumented region.
The Amlogic Meson AO-CEC module is present is Amlogic SoCs and its purpose is to handle communication between HDMI connected devices over the CEC bus.
ESPARSER(Elementary Stream Parser) hardware bitstream parser
ESPARSER is a bitstream parser that outputs to a VIFIFO. Further VDEC blocks then feed from this VIFIFO.
VDEC_1 is a video decoding block that allows decoding of MPEG-1, MPEG-2, MPEG-4 part 2, MJPEG, H.263, H.264, VC-1.
VDEC_HEVC can decode HEVC and VP9.
Both VDEC_1 and VDEC_HEVC share the “vdec” IRQ and as such cannot run concurrently.
VDEC: Video Decoder
FBC Framebuffer Compression
CANVAS is a memory zone where physical memory frames information are stored for the VIU to scanout.
VCLK is the “Pixel Clock” frequency generator from a dedicated PLL.
若有收获，就点个赞吧
0 人点赞
