X265源码解析1-Encode方法

最新推荐文章于 2025-04-30 13:55:11 发布

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本文介绍了X265编码器的`encode`方法，讲解了如何创建和初始化Frame对象，包括分配内存、设置编码起始时间以及拷贝输入YUV数据。还涉及到编码流程中的WaveFront并行处理策略，以及如何进行码率控制和帧的压缩准备工作。

int Encoder::encode(const x265_picture* pic_in, x265_picture* pic_out)

Frame *inFrame;
x265_param* p = (m_reconfigure || m_reconfigureRc) ? m_latestParam : m_param;
if (m_dpb->m_freeList.empty())
{

如果dpb的中没有free状态的Frame，就会去创建。freeList是一个Frame的pool，这样可以节约内存。

inFrame = new Frame;

Frame主要包括编码完成的数据，重建帧的YUV数据和要编码的YUV数据。
inFrame->m_encodeStartTime = x265_mdate();

这一帧的开始时间单位是ms。
if (inFrame->create(p, pic_in->quantOffsets))
{

主要是创建了要存储编码YUV数据的PicYUV，后续再详细分析

/* the first PicYuv created is asked to generate the CU and block unit offset
* arrays which are then shared with all subsequent PicYuv (orig and recon)
* allocated by this top level encoder */
if (m_sps.cuOffsetY)
{
inFrame->m_fencPic->m_cuOffsetY = m_sps.cuOffsetY;
inFrame->m_fencPic->m_buOffsetY = m_sps.buOffsetY;
if (m_param->internalCsp != X265_CSP_I400)
{
inFrame->m_fencPic->m_cuOffsetC = m_sps.cuOffsetC;
inFrame->m_fencPic->m_buOffsetC = m_sps.buOffsetC;
}
}

..........................

}

.......

}

把要编码的YUV数据拷贝到Frame结构体中
inFrame->m_fencPic->copyFromPicture(*pic_in, *m_param, m_sps.conformanceWindow.rightOffset, m_sps.conformanceWindow.bottomOffset);

/* The synchronization of slicetypeDecide is managed here. The findJob() method
* polls the occupancy of the input queue. If the queue is
* full, it will run slicetypeDecide() and output a mini-gop of frames to the
* output queue. If the flush() method has been called (implying no new pictures
* will be received) then the input queue is considered full if it has even one
* picture left. getDecidedPicture() removes pictures from the output queue and
* only blocks as a last resort. It does not start removing pictures until
* m_filled is true, which occurs after *more than* the lookahead depth of
* pictures have been input so slicetypeDecide() should have started prior to
* output pictures being withdrawn. The first slicetypeDecide() will obviously
* still require a blocking wait, but after this slicetypeDecide() will maintain
* its lead over the encoder (because one picture is added to the input queue
* each time one is removed from the output) and decides slice types of pictures
* just ahead of when the encoder needs them */

m_lookahead->addPicture(*inFrame, sliceType);

Manages the wave-front processing of a single encoding frame
class FrameEncoder : public WaveFront, public Thread。wave-font是一种并行处理的方式。

FrameEncoder *curEncoder = m_frameEncoder[m_curEncoder];
m_curEncoder = (m_curEncoder + 1) % m_param->frameNumThreads;
int ret = 0;

/* getEncodedPicture() should block until the FrameEncoder has completed
* encoding the frame. This is how back-pressure through the API is
* accomplished when the encoder is full */
if (!m_bZeroLatency || pass)
outFrame = curEncoder->getEncodedPicture(m_nalList);

/* pop a single frame from decided list, then provide to frame encoder
* curEncoder is guaranteed to be idle at this point */
if (!pass)
frameEnc = m_lookahead->getDecidedPicture();

创建要编码的数据结构

frameEnc->allocEncodeData(m_reconfigure ? m_latestParam : m_param, m_sps);
Slice* slice = frameEnc->m_encData->m_slice;
slice->m_sps = &m_sps;
slice->m_pps = &m_pps;
slice->m_param = m_param;

/* determine references, setup RPS, etc */
m_dpb->prepareEncode(frameEnc);

码率控制

if (m_param->rc.rateControlMode != X265_RC_CQP)
m_lookahead->getEstimatedPictureCost(frameEnc);
slice->m_maxNumMergeCand = m_param->maxNumMergeCand;
slice->m_endCUAddr = slice->realEndAddress(m_sps.numCUs

/* Allow FrameEncoder::compressFrame() to start in the frame encoder thread */开始压缩帧
if (!curEncoder->startCompressFrame(frameEnc))