MPP (Media Process Platform) design (2016.10.12)
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The mpp is a middleware library for Rockchip SoC's cross platform media process.
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The main purpose of mpp is to provide very high performance, high flexibility
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and expansibility on multimedia (mainly video and image) process.
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The design target of mpp is to connect different Rockchip hardware kernel driver
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and different userspace application.
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Rockchip has two sets of hardware kernel driver.
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The first one is vcodec_service/vpu_service/mpp_service which is a high
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performance stateless frame base hardware kernel driver. This driver supports
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all available codecs that hardware can provide. This driver is used on Android/
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Linux.
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The second one is v4l2 driver which is developed for ChromeOS. It currently
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supports H.264/H.265/vp8/vp9. This driver is used on ChomeOS/Linux.
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Mpp plans to support serval userspace applications including OpenMax, FFmpeg,
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gstreamer, libva.
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Feature explaination
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1. Cross Platform
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The target OS platform including Android, Linux, ChromeOS and windows. Mpp uses
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cmake to compile on different platform.
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2. High Performance
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Mpp supports sync / async interface to reduce the time blocked in interface. And
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mpp internally make hardware and software run parallelly. When hardware is
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running sofware will prepare next hardware task at the same time.
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3. High Flexibility
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mpi (Media Process Interface) is easy to extend by different control function.
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The input/output element packet/frame/buffer is easy to extend different
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components.
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System Diagram
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================================================================================
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+---------------------------------------+
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| ffmpeg / OpenMax / gstreamer / libva |
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+---------------------------------------+
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+-------------------- MPP ----------------------+
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| +-------------------------+ +--------+ |
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| | | | | |
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| | MPI / MPP | | | |
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| | buffer queue manage | | | |
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| | | | | |
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| +-------------------------+ | | |
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| +-------------------------+ | | |
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| | codec | | OSAL | |
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| | decoder / encoder | | | |
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| | | | | |
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| +-------------------------+ | | |
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| +-----------+ +-----------+ | | |
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| | parser | | HAL | | | |
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| | control | | reg_gen | | | |
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| +-----------+ +-----------+ +--------| |
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+-------------------- MPP ----------------------+
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+---------------------------------------+
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| kernel |
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| RK vcodec_service / v4l2 |
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+---------------------------------------+
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Mpp is composed of four main sub-modules:
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OSAL (Operation System Abstraction Layer)
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This module shutters the differences between different operation systems and
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provide basic components including memory, time, thread, log and hardware memory
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allocator.
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MPI (Media Process Interface) / MPP
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This module is on charge of interaction with external user. Mpi layer has two
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ways for user. The simple way - User can use put/get packet/frame function set.
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The advanced way - User has to config MppTask and use dequeue/enqueue funciton
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set to communicate with mpp. MppTask can carry different meta data and complete
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complex work.
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Codec (encoder / decoder)
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This module implements the high efficiency internal work flow. The codec module
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provides a general call flow for different video format. Software process will
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be separated from hardware specified process. The software will communicate with
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hardware with a common task interface which combines the buffer information and
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codec specified infomation.
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Parser/Controller and hal (Hardware Abstraction Layer)
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This layer provides the implement function call of different video format and
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different hardware. For decoder parser provide the video stream parse function
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and output format related syntax structure to hal. The hal will translate the
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syntax structure to register set on different hardware. Current hal supports
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vcodec_service kernel driver and plan to support v4l2 driver later.
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