DVSDK码率控制的理解

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我是靠谱客的博主怕孤单寒风，最近开发中收集的这篇文章主要介绍DVSDK码率控制的理解，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

1.动态参数和静态参数：

创建编码器的时候，有params和dynParams两种参数，顾名思义，Venc根据params创建，运行过程中又可以对dynParams改变配置

Venc1_Handle Venc1_create(Engine_Handle hEngine, Char *codecName,

VIDENC1_Params *params,

VIDENC1_DynamicParams *dynParams)

typedef struct IVIDENC1_Params {
XDAS_Int32 size; /**< @sizeField */
XDAS_Int32 encodingPreset; /**< Encoding preset. */
XDAS_Int32 rateControlPreset;/**< @copydoc IVIDEO_RateControlPreset
*
* @sa IVIDEO_RateControlPreset
*/
XDAS_Int32 maxHeight; /**< Maximum height. */
XDAS_Int32 maxWidth; /**< Maximum width. */
XDAS_Int32 maxFrameRate; /**< Maximum frame rate in fps * 1000.
* For example, if max frame rate is 30
* frames per second, set this field
* to 30000.
*/
XDAS_Int32 maxBitRate; /**< Maximum bit rate, bits per second. */
XDAS_Int32 dataEndianness; /**< Endianness of output data.
*
* @sa XDM_DataFormat
*/
XDAS_Int32 maxInterFrameInterval;/**< I to P frame distance. e.g. = 1 if
* no B frames, 2 to insert one B frame.
*
* @remarks This is used for setting the
* maximum number of B frames
* between two refererence frames.
*/
XDAS_Int32 inputChromaFormat;/**< Chroma format for the input buffer.
*
* @sa XDM_ChromaFormat
*/
XDAS_Int32 inputContentType;/**< Video content type of the buffer being
* encoded.
*
* @sa IVIDEO_ContentType
*/
XDAS_Int32 reconChromaFormat;/**< Chroma formats for the reconstruction
* buffers.
*
* @remarks The application should set
* this to #XDM_CHROMA_NA
* if reconstruction
* buffers are not
* required.
*
* @sa XDM_ChromaFormat
*/
} IVIDENC1_Params;

typedef struct IVIDENC1_DynamicParams {
XDAS_Int32 size; /**< @sizeField */
XDAS_Int32 inputHeight; /**< Input frame height. */
XDAS_Int32 inputWidth; /**< Input frame width. */
XDAS_Int32 refFrameRate; /**< Reference, or input, frame rate in
* fps * 1000.
*
* @remarks For example, if ref frame
* rate is 30 frames per second,
* this field will be 30000.
*/
XDAS_Int32 targetFrameRate; /**< Target frame rate in
* fps * 1000.
*
* @remarks For example, if target frame
* rate is 30 frames per second,
* this field will be 30000.
*/
XDAS_Int32 targetBitRate; /**< Target bit rate in bits per second. */
XDAS_Int32 intraFrameInterval;/**< The number of frames between two I
* frames. For example, 30.
*
* @remarks For example, this field will be:
* - 0 - Only first frame to be intra
* coded. e.g. IPPPPPP...
* - 1 - No inter frames (all intra
* frames).
* - 2 - Consecutive IPIPIP... sequence (if
* no B frames).
* - 3 - IPPIPP... or IPBIPBI... and so on.
*/
XDAS_Int32 generateHeader; /**< @copydoc XDM_EncMode
*
* @sa XDM_EncMode
*/
XDAS_Int32 captureWidth; /**< DEFAULT(0): use imagewidth as
* pitch else use given capture
* width for pitch provided it
* is greater than image width.
*/
XDAS_Int32 forceFrame; /**< Force the current (immediate) frame to be
* encoded as a specific frame type.
*
* @remarks For example, this field will be:
* - IVIDEO_NA_FRAME - No forcing of any
* specific frame type for the frame.
* - IVIDEO_I_FRAME - Force the frame to be
* encoded as I frame.
* - IVIDEO_IDR_FRAME - Force the frame to
* be encoded as an IDR frame (specific
* to H.264 codecs).
* - IVIDEO_P_FRAME - Force the frame to be
* encoded as a P frame.
* - IVIDEO_B_FRAME - Force the frame to be
* encoded as a B frame.
*
* @sa IVIDEO_FrameType.
*/
XDAS_Int32 interFrameInterval;/**< Number of B frames between two reference
* frames; that is, the number of B frames
* between two P frames or I/P frames.
* DEFAULT(0).
*
* @remarks For example, this field will be:
* - 0 - to use maxInterFrameInterval.
* - 1 - 0 B frames between two reference
* frames.
* - 2 - 1 B frame between two reference
* frames.
* - 3 - 2 B frames between two reference
* frames.
* - and so on...
*
* @sa IVIDENC1_Params.maxInterFrameInterval.
*/
XDAS_Int32 mbDataFlag; /**< Flag to indicate that the algorithm should
* use MB data supplied in additional buffer
* within inBufs.
*/
} IVIDENC1_DynamicParams;

2.重要参数

若要进行码率和帧率控制，首先静态参数中，rateControlPreset是非常重要的一个参数，可选项有以下五种，其中CBR和VBR是我们要进行选择的，若不需要对码率帧率控制可直接选择NONE。

CBR编码时，在配置为较低比特率的时候，帧率也会随之下降，若采用VBR编码，可以始终保持较高的帧率，因为CBR是很定比特率编码，而VBR是根据图片复杂度优化。较少的变化采用较少的bit，复杂的地方采用较多的bit。因此码率较高的时候，CBR速度快，码率低的时候VBR较能改变图片质量。

IVIDEO_LOW_DELAY = 1, /**< CBR rate control for video conferencing. */
IVIDEO_STORAGE = 2, /**< VBR rate control for local storage (DVD)
* recording.
*/
IVIDEO_TWOPASS = 3, /**< Two pass rate control for non real time
* applications.
*/
IVIDEO_NONE = 4, /**< No configurable video rate control
* mechanism.
*/
IVIDEO_USER_DEFINED = 5,/**< User defined configuration using extended
* parameters.

在动态参数中，有两个值是同一个意思，可能是为了兼容性考虑，targetFrameRate是DM6467要配置的，refFrameRate虽然可以置之不理，但是当两个值设置为一致时，配置才不会报错，

XDAS_Int32 refFrameRate; /**< Reference, or input, frame rate in
* fps * 1000.
*
* @remarks For example, if ref frame
* rate is 30 frames per second,
* this field will be 30000.
*/
XDAS_Int32 targetFrameRate; /**< Target frame rate in
* fps * 1000.
*
* @remarks For example, if target frame
* rate is 30 frames per second,
* this field will be 30000.
*/