转载： https://geek.csdn.net/65e5982f9a0b6f536f0c0e36.html
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
① 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。② 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。③ 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。④ 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。
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解码文件：
Video_Decoder_API_Guide.pdf
https://blog.csdn.net/TheDayIn_CSDN/article/details/86582797
视频编解码（五）：解码器驱动代码理解
一、结构体定义的方法
VideoStreamInfo mVideoInfo1 = 0;
VideoStreamInfo *pVideoInfo1 = &mVideoInfo1;
VideoStreamInfo *pp = (VideoStreamInfo *)malloc(sizeof(VideoStreamInfo));
free(pp);二、指针分配内存方法：
int *data_count1;
data_count1 = (int*)malloc(sizeof(int));
memset(data_count1, 0, sizeof(int));三、码流提取
指针
动态内存非配
命名规则
fread()/fseek()指针跳转
fseek()
fseek(fp,0L,SEEK_END);末尾 0L代表偏移位数（可以为负）
fseek(fp,0L,SEEK_CUR);当前
fseek(fp,0L,SEEK_SET);开始
fopen(w)和fopen(ab) ab 代表连续写
四、解码器申请内存
VideoStreamInfo mVideoInfo1;
VideoStreamInfo* pVideoInfo1 = &mVideoInfo1 ;
pSpecilData1 = (char*)malloc(SPEC_DATA_SIZE);五、读取码流文件
fread(&pVideoInfo1->eCodecFormat, 1, sizeof(int), fp);六、解码器基本数据结构
VideoStreamInfo mVideoInfo1;
mVideoInfo1.eCodecFormat = VIDEO_CODEC_FORMAT_H263; 编码格式
VConfig vConfig;
extra frame buffer=
vConfig.nDisplayHoldingFrameBufferNum = 5;
vConfig.nRotateHoldingFrameBufferNum = 5;
vConfig.nDecodeSmoothFrameBufferNum = 5;七、申请内存
struct ScMemOpsS* memops = MemAdapterGetOpsS();
vConfig.memops = memops;八、基本数据结构
码流基本信息 ：mVideoInfo1
解码器配置信息： vConfig
InitializeVideoDecoder(pVideo, &mVideoInfo1, &vConfig)
九、请求码流
datalen: 码流数据一笔一笔
RequestVideoStreamBuffer(pVideo,
dataLen,
(char**)&buf,
&buflen,
(char**)&ringBuf,
&ringBufLen,
0)buffer循环方法
if(buflen >= dataLen)
{
memcpy(buf,AwspData,dataLen); //copy data to buf
}
else{
memcpy(buf,AwspData,buflen); //the first part of data
memcpy(ringBuf,AwspData+buflen,dataLen - buflen); //the left part of data
}一笔码流数据是否开始结束
DataInfo.bIsFirstPart = 1;
DataInfo.bIsLastPart = 1;
VideoStreamDataInfo DataInfo; 码流数据信息
SubmitVideoStreamData(pVideo, &DataInfo, 0)
DecodeVideoStream(pVideo, endofstream, decodekeyframeonly,
dropBFrameifdelay, currenttimeus);十、返回值
VDECODE_RESULT_UNSUPPORTED = -1,
VDECODE_RESULT_OK = 0,
VDECODE_RESULT_FRAME_DECODED = 1,
VDECODE_RESULT_CONTINUE = 2,
VDECODE_RESULT_KEYFRAME_DECODED = 3,
VDECODE_RESULT_NO_FRAME_BUFFER = 4,
VDECODE_RESULT_NO_BITSTREAM = 5,
VDECODE_RESULT_RESOLUTION_CHANGE = 6,（11）内存：
#ifdef #else #endif （如果定义执行1） 只能判断一个宏
#ifndef #else #endif （如果定义执行1）
DMA_HEAP（连续内存）、SYSTEM_HEAP（非连续内存）
CACHED_FLAG（自动同步）、SUNC_FLAG（手动同步）
#if #elif #else #endif （判断多个宏）
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