我通过live555打开本地的SDP文件，然后通过这个文件为我的IP Camera建立个传输会话，已经成功，DummySink中的 afterGettingFrame这回调函数能不间断的调用，我直接把表示每帧fReceiveBuffer和frameSize传入了FFMPEG的解码器，但是 avcodec_decode_video2总是调用失败。我查看了一些帧的fReceiveBuffer，里面没有插入相关的SPS和PPS，没有0x00000001的标记，因为解码器要解码IDR帧必须通过SPS和PPS正确初始化，才能够解码，我的SDP文件里面有PPS和SPS的Base64编码，我需要怎么处理这个SPS和PPS才能正确初始化解码器？不然解码器是无法解码H264的。FFMPEG中的AVCodecContext中的extradata也没有相关文档描述怎么用，听说是用来存放SPS和PPS的，如果是，该怎么用？我需要把SPS和PPS的Base64的编码解出来再传入吗？还是直接就传入（插入）SPS和PPS的Base64版本？

以下是我的代码片断：

void afterGettingFrame(unsigned frameSize, unsigned numTruncatedBytes, struct timeval presentationTime, unsigned durationInMicroseconds) { if (fStreamId != NULL) envir() << "Stream \"" << fStreamId << "\"; "; envir() << fSubsession.mediumName() << "/" << fSubsession.codecName() << ":\tReceived " << frameSize << " bytes"; if (numTruncatedBytes > 0) envir() << " (with " << numTruncatedBytes << " bytes truncated)"; char uSecsStr[6 + 1]; // used to output the 'microseconds' part of the presentation time sprintf_s(uSecsStr, 7, "%06u", (unsigned)presentationTime.tv_usec); envir() << ".\tPresentation time: " << (int)presentationTime.tv_sec << "." << uSecsStr; gffmpeg->decodeFrame(fReceiveBuffer, frameSize, presentationTime.tv_sec, presentationTime.tv_usec); // Then continue, to request the next frame of data: continuePlaying(); }

void QFFmpeg::decodeFrame(uint8_t* frameBuffer, int frameLength, long second, long microSecond) { if (frameLength <= 0) return; int frameFinished = 0; AVPacket framePacket; av_init_packet(&framePacket); framePacket.size = frameLength; framePacket.data = frameBuffer; int ret = avcodec_decode_video2(m_pAVCodecContext, m_pAVFrame, &frameFinished, &framePacket); if (ret < 0) { qDebug() << "Decode error"; return; } if (frameFinished) { m_playMutex.lock(); m_videoWidth = m_pAVFrame->width; m_videoHeight = m_pAVFrame->height; m_pSwsContext = sws_getContext(m_videoWidth, m_videoHeight, AVPixelFormat::AV_PIX_FMT_YUV420P, m_videoWidth, m_videoHeight, AVPixelFormat::AV_PIX_FMT_RGB24, SWS_BICUBIC, 0, 0, 0); sws_scale(m_pSwsContext, (const uint8_t* const *)m_pAVFrame->data, m_pAVFrame->linesize, 0, m_videoHeight, m_pAVPicture.data, m_pAVPicture.linesize); char timestamp[100]; sprintf_s(timestamp, 100, "Time Stamp is: %ld.%ld", second, microSecond); //发送获取一帧图像信号 QImage image(m_pAVPicture.data[0], m_videoWidth, m_videoHeight, QImage::Format_RGB888); QPainter pen(&image); pen.setPen(Qt::white); pen.setFont(QFont("Times", 10, QFont::Bold)); pen.drawText(image.rect(), Qt::AlignBottom, QString(timestamp)); emit GetImage(image); m_playMutex.unlock(); } }

以下是解码器的初始化，都能正确返回

bool QFFmpeg::Init() { m_pAVCodec = avcodec_find_decoder(AV_CODEC_ID_H264); if (!m_pAVCodec) return false; m_pAVCodecContext = avcodec_alloc_context3(m_pAVCodec); if (avcodec_open2(m_pAVCodecContext, m_pAVCodec, NULL) < 0) return false; return true; }