硬件解码器API接口对比(google decoder-allwinner decoder)

迈不过友情╰ 2022-11-11 05:14 47阅读 0赞

# Google Decoder API #

/* Decoder client interface. */
    typedef void* ClientInst; /* Opaque pointer to the client. */
    
    /* Function to notify the client that decoder has successfully initialized. */
    typedef void ClientInitialized(ClientInst inst);
    /* Function to notify about successful decoding of the stream parameters. * Decoder expects client to provide needed buffers through DecSetPictureBuffers * function to continue decoding the actual stream. */
    typedef void ClientHeadersDecoded(ClientInst inst,
                                      struct DecSequenceInfo sequence_info);
    /* Function to notify client that a buffer has been consumed by the decoder and * it can be handled freely by the client. */
    typedef void ClientBufferDecoded(ClientInst inst, struct DecInput* input);
    typedef void ClientStreamDecoded(ClientInst inst);
    /* Function to notify about successful decoding of a picture. * This is just a notification, no action expected from client. */
    typedef void ClientPictureDecoded(ClientInst inst,
                                      struct DecDecodedPictureInfo info);
    /* Function to notify about picture that is ready to be output. Client is * expected to notify the decoder when it has finished processing the picture, * so decoder can reuse the picture buffer for another picture. * picture_secondary may be used again with show_existing_frame so it should * not be modified in the callback function */
    typedef void ClientPictureReady(ClientInst inst, struct DecPicture picture,
                                    struct DecPicture picture_secondary);
    /* Function to notify the client that all the pending pictures have been * outputted and decoder can be safely shut down. */
    typedef void ClientEndOfStream(ClientInst inst);
    /* Function to notify the client that decoder has shut down. */
    typedef void ClientReleased(ClientInst inst);
    /* Function to notify client about error in the decoding process. */
    typedef void ClientNotifyError(ClientInst inst, u32 pic_id, enum DecRet rv);
    
    /* Datatype to package information about client instance for decoder's use. */
    struct DecClientHandle { 
      ClientInst client;
      ClientInitialized* Initialized;
      ClientHeadersDecoded* HeadersDecoded;
      ClientBufferDecoded* BufferDecoded;
      ClientStreamDecoded* StreamDecoded;
      ClientPictureDecoded* PictureDecoded;
      ClientPictureReady* PictureReady;
      ClientEndOfStream* EndOfStream;
      ClientReleased* Released;
      ClientNotifyError* NotifyError;
    };
    
    /* Decoder interface. */
    typedef const void* DecInst; /* Opaque pointer to the decoder instance. */
    
    /* Function to query build information about the software and hardware build of * the underlying hardware decoder. */
    struct DecSwHwBuild DecGetBuild(void);
    
    /* Function to initialize the decoder. Functionality provided by the client to * the component are collected into the callbacks parameter. Client is expected * to outlive the decoder component, i.e. the callbacks and instance given in * callbacks parameter must be valid until client has successfully executed * a call to DecRelease function. */
    enum DecRet DecInit(enum DecCodec codec, DecInst* decoder,
                        struct DecConfig config, struct DecClientHandle callbacks,
                        void *cwl);
    
    /* Function to dispatch a buffer containing video bitstream to be decoded by the * component. Buffer can be reused after the function has returned, during the * call the buffer must not be written into. */
    enum DecRet DecDecode(DecInst dec_inst, const struct DecInput* input);
    
    /* Function to assign picture buffers for the decoder. When decoder has finished * decoding the stream headers and knows which types of buffers and how many of * them it will need, it will inform that through the HeadersDecoded callback. * Buffers must not be written into until client has successfully called * DecRelease or decoder has requested new set of buffers through HeadersDecoded * callback. */
    enum DecRet DecSetPictureBuffers(DecInst dec_inst,
                                     const struct CWLLinearMem* buffers,
                                     u32 num_of_buffers);
    
    /* Function to tell the decoder that client has finished processing a specific * picture that was previously sent to client through the PictureReady callback. */
    enum DecRet DecPictureConsumed(DecInst dec_inst, struct DecPicture picture);
    
    /* Function to tell the decoder that it should not be expecting any more input * stream and Finish decoding and outputting all the buffers that are currently * pending in the component. Once decoder has finished outputting the pending * pictures it will notify the client about it by calling the EndOfStream * callback. */
    enum DecRet DecEndOfStream(DecInst dec_inst);
    
    /* Function to release the decoder instance. When the function returns decoder * has released all the resources it has acquired. */
    void DecRelease(DecInst dec_inst);

# Awinner Deocder API #

typedef void* VideoDecoder;
    VideoDecoder* CreateVideoDecoder(void);
    void DestroyVideoDecoder(VideoDecoder* pDecoder);
    int InitializeVideoDecoder(VideoDecoder* pDecoder,
                         VideoStreamInfo* pVideoInfo,
                         VConfig* pVconfig);
    void ResetVideoDecoder(VideoDecoder* pDecoder);
    int DecodeVideoStream(VideoDecoder* pDecoder,
                          int           bEndOfStream,
                          int           bDecodeKeyFrameOnly,
                          int           bDropBFrameIfDelay,
                          int64_t       nCurrentTimeUs);
    int RequestVideoStreamBuffer(VideoDecoder* pDecoder,
                                 int           nRequireSize,
                                 char**        ppBuf,
                                 int*          pBufSize,
                                 char**        ppRingBuf,
                                 int*          pRingBufSize,
                                 int           nStreamBufIndex);
    int SubmitVideoStreamData(VideoDecoder*        pDecoder,
                              VideoStreamDataInfo* pDataInfo,
                              int                  nStreamBufIndex);
    VideoPicture* RequestPicture(VideoDecoder* pDecoder, int nStreamIndex);
    int ReturnPicture(VideoDecoder* pDecoder, VideoPicture* pPicture);

# API对比分析 #

## 内存消耗 ##

在输入数据方面，google dec内部没有缓存，allwiner dec有缓存；输出数据方面，两者都有缓存，在内部实现其他存储相同情况下，google dec需要更小的空间。

## 性能分析 ##

在输出图像方面，google dec采用回调的方式通知用户可用的输出图像；而allwinner dec采用轮询的方式，通过轮询接口来查询是否有输出图像。  
在输入数据方面，由于内部没有输入缓存，google dec同样采用回调方式通知用户输入buffer已被消费，从而实现异步操作；而allwinner dec由于有输入缓存，可直接实现异步。  
为了实现异步，两者的实现有所不同：  
google dec: 内部需实现deocder线程，才能使输入buffer已被消费的回调函数实现在另一线程上，实现异步。同理也需要一个output线程查询输出缓存，并回调给用户。  
allwinner dec： 内部无任何线程，需要用户自己安排好各API所运行的线程，相应的同步机制也需要用户实现，由于缓存外部不可见，API接口只提供轮询机制，性能上有所损失。

## 灵活性 ##

google dec：输入缓存用户可自己设计，提高灵活性，但未提供复位操作，无法实现刷新内部缓存的操作，在需要跳播的场景，google dec无能为力。输出buffer地址只能由外部设置。  
allwiner dec：提供复位操作，可实现跳播等场景。输出buffer地址可由内部申请，也可由外部设置。

# 总结 #

总体来说google dec api更合理一点，将两者的优势结合一下，可以更合理。