本文详细解析了x265编码器中的encode()函数，包括其主要功能、内部流程及关键变量的作用。通过分析可知，该函数负责处理输入帧并输出编码后的帧。
转载于：https://blog.youkuaiyun.com/frd2009041510/article/details/51150318
非常感谢原作者的详细分析，再次表示感谢。
在x265中，main()函数中调用了encoder_encode()函数，而encoder_encode()函数调用了encode()函数，encode()函数的主要功能是输入一帧图像，得到一帧图像的输出。
encode()函数主要包括大致三个部分：
（1）分析是否由于错误造成的代码终止，如g_checkFailures、m_aborted。
（2）判断是否有输入帧，若有，则判断该输入帧的像素深度、颜色空间是否支持，并判断List是否为空，若为空则创建；除此之外，还有一个比较重要的变量，即ret，此处初始化了ret为0，ret用于判断encode()函数的执行状况，0代表当前没有可供输出的重构帧，则返回encoder_encode()函数进行处理，1代表有输出，从encode()函数的最后一行代码return ret可以证实这一点。
（3）用一个do/while()判断是否有输出，若有则ret为1，并且调用了startCompressFrame()函数，startCompressFrame()函数的主要目的就是触发线程，为进一步的编码做准备。
对应的代码分析如下：
- /*=============================================================*/
- /*
- ====== Analysed by: RuiDong Fang
- ====== Csdn Blog: http://blog.youkuaiyun.com/frd2009041510
- ====== Date: 2016.04.14
- ====== Funtion： encode()函数,Feed one new input frame into the encoder, get one frame out.
- */
- /*=============================================================*/
- /**
- * Feed one new input frame into the encoder, get one frame out. If pic_in is
- * NULL, a flush condition is implied and pic_in must be NULL for all subsequent
- * calls for this encoder instance.
- *
- * pic_in input original YUV picture or NULL
- * pic_out pointer to reconstructed picture struct
- *
- * returns 0 if no frames are currently available for output
- * 1 if frame was output, m_nalList contains access unit
- * negative on malloc error or abort */
- int Encoder::encode(const x265_picture* pic_in, x265_picture* pic_out)
- {
- ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////1
- #if CHECKED_BUILD || _DEBUG
- if (g_checkFailures)
- {
- x265_log(m_param, X265_LOG_ERROR, "encoder aborting because of internal error\n");
- return -1;
- }
- #endif
- if (m_aborted)
- return -1;
- if (m_exportedPic)
- {
- ATOMIC_DEC(&m_exportedPic->m_countRefEncoders);
- m_exportedPic = NULL;
- m_dpb->recycleUnreferenced();
- }
- ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////2
- //若有输入时
- if (pic_in)
- {
- //判断输入帧的颜色空间是否支持，若不支持，打印错误
- if (pic_in->colorSpace != m_param->internalCsp)
- {
- x265_log(m_param, X265_LOG_ERROR, "Unsupported color space (%d) on input\n",
- pic_in->colorSpace);
- return -1;
- }
- //输入的每一帧的深度必须处于8至16范围内
- if (pic_in->bitDepth < 8 || pic_in->bitDepth > 16)
- {
- x265_log(m_param, X265_LOG_ERROR, "Input bit depth (%d) must be between 8 and 16\n",
- pic_in->bitDepth);
- return -1;
- }
- Frame *inFrame;
- if (m_dpb->m_freeList.empty()) //若List为空，则创建
- {
- inFrame = new Frame;
- x265_param* p = m_reconfigured? m_latestParam : m_param;
- if (inFrame->create(p))
- {
- /* 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_cuOffsetY)
- {
- inFrame->m_fencPic->m_cuOffsetC = m_cuOffsetC;
- inFrame->m_fencPic->m_cuOffsetY = m_cuOffsetY;
- inFrame->m_fencPic->m_buOffsetC = m_buOffsetC;
- inFrame->m_fencPic->m_buOffsetY = m_buOffsetY;
- }
- else
- {
- if (!inFrame->m_fencPic->createOffsets(m_sps))
- {
- m_aborted = true;
- x265_log(m_param, X265_LOG_ERROR, "memory allocation failure, aborting encode\n");
- inFrame->destroy();
- delete inFrame;
- return -1;
- }
- else
- {
- m_cuOffsetC = inFrame->m_fencPic->m_cuOffsetC;
- m_cuOffsetY = inFrame->m_fencPic->m_cuOffsetY;
- m_buOffsetC = inFrame->m_fencPic->m_buOffsetC;
- m_buOffsetY = inFrame->m_fencPic->m_buOffsetY;
- }
- }
- }
- else
- {
- m_aborted = true;
- x265_log(m_param, X265_LOG_ERROR, "memory allocation failure, aborting encode\n");
- inFrame->destroy();
- delete inFrame;
- return -1;
- }
- }
- else //若List不为空，则popBack
- {
- inFrame = m_dpb->m_freeList.popBack();
- inFrame->m_lowresInit = false;
- }
- /* Copy input picture into a Frame and PicYuv, send to lookahead */
- inFrame->m_fencPic->copyFromPicture(*pic_in, m_sps.conformanceWindow.rightOffset, m_sps.conformanceWindow.bottomOffset);
- inFrame->m_poc = ++m_pocLast;
- inFrame->m_userData = pic_in->userData;
- inFrame->m_pts = pic_in->pts;
- inFrame->m_forceqp = pic_in->forceqp;
- inFrame->m_param = m_reconfigured ? m_latestParam : m_param;
- if (m_pocLast == 0) //若POC=0
- m_firstPts = inFrame->m_pts;
- if (m_bframeDelay && m_pocLast == m_bframeDelay)
- m_bframeDelayTime = inFrame->m_pts - m_firstPts;
- /* Encoder holds a reference count until stats collection is finished */
- ATOMIC_INC(&inFrame->m_countRefEncoders);
- if ((m_param->rc.aqMode || m_param->bEnableWeightedPred || m_param->bEnableWeightedBiPred) &&
- (m_param->rc.cuTree && m_param->rc.bStatRead))
- {
- if (!m_rateControl->cuTreeReadFor2Pass(inFrame))
- {
- m_aborted = 1;
- return -1;
- }
- }
- /* Use the frame types from the first pass, if available */
- int sliceType = (m_param->rc.bStatRead) ? m_rateControl->rateControlSliceType(inFrame->m_poc) : pic_in->sliceType;
- /* In analysisSave mode, x265_analysis_data is allocated in pic_in and inFrame points to this */
- /* Load analysis data before lookahead->addPicture, since sliceType has been decided */
- if (m_param->analysisMode == X265_ANALYSIS_LOAD)
- {
- x265_picture* inputPic = const_cast<x265_picture*>(pic_in);
- /* readAnalysisFile reads analysis data for the frame and allocates memory based on slicetype */
- readAnalysisFile(&inputPic->analysisData, inFrame->m_poc);
- inFrame->m_analysisData.poc = inFrame->m_poc;
- inFrame->m_analysisData.sliceType = inputPic->analysisData.sliceType;
- inFrame->m_analysisData.numCUsInFrame = inputPic->analysisData.numCUsInFrame;
- inFrame->m_analysisData.numPartitions = inputPic->analysisData.numPartitions;
- inFrame->m_analysisData.interData = inputPic->analysisData.interData;
- inFrame->m_analysisData.intraData = inputPic->analysisData.intraData;
- sliceType = inputPic->analysisData.sliceType;
- }
- m_lookahead->addPicture(*inFrame, sliceType);
- m_numDelayedPic++;
- }
- else //若没有输入
- m_lookahead->flush();
- FrameEncoder *curEncoder = m_frameEncoder[m_curEncoder];
- m_curEncoder = (m_curEncoder + 1) % m_param->frameNumThreads; //当前要编码的帧
- /*ret用于判断该整体函数的状况：
- 若当前没有可供输出的帧则为0（if no frames are currently available for output），
- 否则为1（1 if frame was output, m_nalList contains access unit negative on malloc error or abort）。*/
- int ret = 0;
- /* Normal operation is to wait for the current frame encoder to complete its current frame
- * and then to give it a new frame to work on. In zero-latency mode, we must encode this
- * input picture before returning so the order must be reversed. This do/while() loop allows
- * us to alternate the order of the calls without ugly code replication */
- Frame* outFrame = NULL;
- Frame* frameEnc = NULL;
- int pass = 0;
- ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////3
- //do/while() loop
- do
- {
- /* 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);
- if (outFrame)
- {
- Slice *slice = outFrame->m_encData->m_slice;
- x265_frame_stats* frameData = NULL;
- /* Free up pic_in->analysisData since it has already been used */
- if (m_param->analysisMode == X265_ANALYSIS_LOAD)
- freeAnalysis(&outFrame->m_analysisData);
- if (pic_out) //若有输出
- {
- PicYuv *recpic = outFrame->m_reconPic;
- pic_out->poc = slice->m_poc;
- pic_out->bitDepth = X265_DEPTH;
- pic_out->userData = outFrame->m_userData;
- pic_out->colorSpace = m_param->internalCsp;
- frameData = &(pic_out->frameData);
- pic_out->pts = outFrame->m_pts;
- pic_out->dts = outFrame->m_dts;
- //判断该帧的类型--I/P/B
- switch (slice->m_sliceType)
- {
- case I_SLICE:
- pic_out->sliceType = outFrame->m_lowres.bKeyframe ? X265_TYPE_IDR : X265_TYPE_I;
- break;
- case P_SLICE:
- pic_out->sliceType = X265_TYPE_P;
- break;
- case B_SLICE:
- pic_out->sliceType = X265_TYPE_B;
- break;
- }
- pic_out->planes[0] = recpic->m_picOrg[0];
- pic_out->stride[0] = (int)(recpic->m_stride * sizeof(pixel));
- pic_out->planes[1] = recpic->m_picOrg[1];
- pic_out->stride[1] = (int)(recpic->m_strideC * sizeof(pixel));
- pic_out->planes[2] = recpic->m_picOrg[2];
- pic_out->stride[2] = (int)(recpic->m_strideC * sizeof(pixel));
- /* Dump analysis data from pic_out to file in save mode and free */
- if (m_param->analysisMode == X265_ANALYSIS_SAVE)
- {
- pic_out->analysisData.poc = pic_out->poc;
- pic_out->analysisData.sliceType = pic_out->sliceType;
- pic_out->analysisData.numCUsInFrame = outFrame->m_analysisData.numCUsInFrame;
- pic_out->analysisData.numPartitions = outFrame->m_analysisData.numPartitions;
- pic_out->analysisData.interData = outFrame->m_analysisData.interData;
- pic_out->analysisData.intraData = outFrame->m_analysisData.intraData;
- writeAnalysisFile(&pic_out->analysisData);
- freeAnalysis(&pic_out->analysisData);
- }
- }
- if (slice->m_sliceType == P_SLICE)
- {
- if (slice->m_weightPredTable[0][0][0].bPresentFlag)
- m_numLumaWPFrames++;
- if (slice->m_weightPredTable[0][0][1].bPresentFlag ||
- slice->m_weightPredTable[0][0][2].bPresentFlag)
- m_numChromaWPFrames++;
- }
- else if (slice->m_sliceType == B_SLICE)
- {
- bool bLuma = false, bChroma = false;
- for (int l = 0; l < 2; l++)
- {
- if (slice->m_weightPredTable[l][0][0].bPresentFlag)
- bLuma = true;
- if (slice->m_weightPredTable[l][0][1].bPresentFlag ||
- slice->m_weightPredTable[l][0][2].bPresentFlag)
- bChroma = true;
- }
- if (bLuma)
- m_numLumaWPBiFrames++;
- if (bChroma)
- m_numChromaWPBiFrames++;
- }
- if (m_aborted)
- return -1;
- finishFrameStats(outFrame, curEncoder, curEncoder->m_accessUnitBits, frameData);
- /* Write RateControl Frame level stats in multipass encodes */
- if (m_param->rc.bStatWrite)
- if (m_rateControl->writeRateControlFrameStats(outFrame, &curEncoder->m_rce))
- m_aborted = true;
- /* Allow this frame to be recycled if no frame encoders are using it for reference */
- if (!pic_out)
- {
- ATOMIC_DEC(&outFrame->m_countRefEncoders);
- m_dpb->recycleUnreferenced();
- }
- else
- m_exportedPic = outFrame;
- m_numDelayedPic--;
- ret = 1; //有输出，则ret为1
- }
- /* 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();
- if (frameEnc && !pass)
- {
- /* give this frame a FrameData instance before encoding */
- if (m_dpb->m_picSymFreeList)
- {
- frameEnc->m_encData = m_dpb->m_picSymFreeList;
- m_dpb->m_picSymFreeList = m_dpb->m_picSymFreeList->m_freeListNext;
- frameEnc->reinit(m_sps);
- }
- else
- {
- frameEnc->allocEncodeData(m_param, m_sps);
- Slice* slice = frameEnc->m_encData->m_slice;
- slice->m_sps = &m_sps;
- slice->m_pps = &m_pps;
- slice->m_maxNumMergeCand = m_param->maxNumMergeCand;
- slice->m_endCUAddr = slice->realEndAddress(m_sps.numCUsInFrame * NUM_4x4_PARTITIONS);
- frameEnc->m_reconPic->m_cuOffsetC = m_cuOffsetC;
- frameEnc->m_reconPic->m_cuOffsetY = m_cuOffsetY;
- frameEnc->m_reconPic->m_buOffsetC = m_buOffsetC;
- frameEnc->m_reconPic->m_buOffsetY = m_buOffsetY;
- }
- curEncoder->m_rce.encodeOrder = m_encodedFrameNum++;
- if (m_bframeDelay)
- {
- int64_t *prevReorderedPts = m_prevReorderedPts;
- frameEnc->m_dts = m_encodedFrameNum > m_bframeDelay
- ? prevReorderedPts[(m_encodedFrameNum - m_bframeDelay) % m_bframeDelay]
- : frameEnc->m_reorderedPts - m_bframeDelayTime;
- prevReorderedPts[m_encodedFrameNum % m_bframeDelay] = frameEnc->m_reorderedPts;
- }
- else
- frameEnc->m_dts = frameEnc->m_reorderedPts;
- /* Allocate analysis data before encode in save mode. This is allocated in frameEnc */
- if (m_param->analysisMode == X265_ANALYSIS_SAVE)
- {
- x265_analysis_data* analysis = &frameEnc->m_analysisData;
- analysis->poc = frameEnc->m_poc;
- analysis->sliceType = frameEnc->m_lowres.sliceType;
- uint32_t widthInCU = (m_param->sourceWidth + g_maxCUSize - 1) >> g_maxLog2CUSize;
- uint32_t heightInCU = (m_param->sourceHeight + g_maxCUSize - 1) >> g_maxLog2CUSize;
- uint32_t numCUsInFrame = widthInCU * heightInCU;
- analysis->numCUsInFrame = numCUsInFrame;
- analysis->numPartitions = NUM_4x4_PARTITIONS;
- allocAnalysis(analysis);
- }
- /* determine references, setup RPS, etc */
- m_dpb->prepareEncode(frameEnc); //========================准备编码前的一些工作，如决定参考帧,设置RPS等等
- if (m_param->rc.rateControlMode != X265_RC_CQP)
- m_lookahead->getEstimatedPictureCost(frameEnc);
- /* Allow FrameEncoder::compressFrame() to start in the frame encoder thread */
- if (!curEncoder->startCompressFrame(frameEnc)) //========================编码线程的开始，调用了startCompressFrame()函数，而startCompressFrame()调用了m_enable.trigger()以触发线程
- m_aborted = true;
- }
- else if (m_encodedFrameNum)
- m_rateControl->setFinalFrameCount(m_encodedFrameNum);
- }
- while (m_bZeroLatency && ++pass < 2);
- return ret;
- }
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