Openmax (OMX) framework

This article is divided into two parts to explain

Codec  In section  AwesomePlayer  To  OMX  service

Previously, I introduced NuPlayer The final decoding will arrive OMX frame , That is to say  OpenMAX frame , This paper begins to analyze the AwesomePlayer To OMX Service process , That is to say, open OpenMAX Prepare relevant contents .Android Used in the system OpenMAX To encode and decode ,Android An upward abstraction   layer OMXCodec, Provide to the upper player AwesomePlayer Use . There's a IOMX Interface , stay ACodec  Through IOMX call OpenMAX Components . Audio and video decoder in player mVideoSource、 mAudioSource  All are  OMXCodec  Example .OMXCodec::Create It is the entrance of decoder initialization .OMXCodec adopt IOMX rely on Binder Mechanism acquisition  OMX service ,OMX Service is OpenMAX stay Android In the implementation of .

OpenMAX And StageFright The hierarchical framework of

StageFright The framework passes OpenMAX Communicate with the hardware layer , chart 1 yes OpenMAX and StageFright Of   Hierarchy diagram . In the figure 1 Can be seen in ,StrageFright There are two routes to the floor OpenMAX frame °  All the way through NuPlayer  arrive ACodec class , Then call directly OMX IL Core The interface . The other way is through StagefrightPlayer To  AwesomePlayer, And then arrive at 0MXCodec class , And then call OMX Component interface for data transmission . In the past AwesomePlayer in , Audio and video data will arrive OMXCodec Search for the corresponding decoder in   decode , Pictured 2 Shown ：IOMX and OMX Components through Binder signal communication , The middle also involves OMXClient.OMX  Medium OMXNodelnstance Responsible for creating and maintaining different instances , These instances are created according to the above requirements , With  Node As only … identification . So every one of the players OMXCodec stay OMX The server side has its own corresponding  OMXNodelnstance example .OMXMaster Maintain the underlying software and hardware decoding library , according to OMXNodelnstance I want to   To create a decoding entity component .

OpenMAX and StageFright The hierarchy diagram of

AwesomePlayer  And  OMX  The relationship between