从AVPacket填充CMediaType和IMediaSample以获取h264视频 [英] Filling CMediaType and IMediaSample from AVPacket for h264 video

问题描述

我搜索后几乎没有发现任何东西，所以我非常感谢我的问题。

我正在编写一个使用libav读取的DirectShow源过滤器并从youtube的FLV文件发送下游h264数据包。但是我找不到合适的libav结构的字段来正确实现过滤器的GetMediType（）和FillBuffer（）。一些libav字段为空。结果h264解码器在尝试处理接收到的数据时崩溃。

我在哪里错了？在使用libav或DirectShow接口时？在使用libav时，也许h264需要额外的处理，还是我填写的参考时间不正确？有人有任何有用的链接可用于使用libav编写DirectShow h264源过滤器吗？

GetMediaType（）的一部分：

  VIDEOINFOHEADER * pvi =（VIDEOINFOHEADER *）toMediaType-> AllocFormatBuffer（sizeof（VIDEOINFOHEADER））; 
 pvi-> AvgTimePerFrame = UNITS_PER_SECOND / m_pFormatContext-> streams [m_streamNo]->编解码器-> sample_rate; // sample_rate为0 
 pvi-> dwBitRate = m_pFormatContext-> bit_rate; 
 pvi-> rcSource = videoRect; 
 pvi-> rcTarget = videoRect; 
 
 //位图
 pvi-> bmiHeader.biSize = sizeof（BITMAPINFOHEADER）; 
 pvi-> bmiHeader.biWidth = videoRect.right; 
 pvi-> bmiHeader.biHeight = videoRect.bottom; 
 pvi-> bmiHeader.biPlanes = 1; 
 pvi-> bmiHeader.biBitCount = m_pFormatContext-> streams [m_streamNo]->编解码器-> bits_per_raw_sample; //或此处应该是bits_per_coded_sample 
 pvi-> bmiHeader.biCompression = FOURCC_H264; 
 pvi-> bmiHeader.biSizeImage = GetBitmapSize（& pvi-> bmiHeader）; 
  

FillBuffer（）的一部分：

  //获取缓冲区指针
 BYTE * pBuffer = NULL; 
 if（pSamp-> GetPointer（& pBuffer）< 0）
返回S_FALSE; 
 
 //获取下一个数据包
 AVPacket * pPacket = m_mediaFile.getNextPacket（）; 
 if（pPacket-> data == NULL）
返回S_FALSE; 
 
 //如果（pSamp-> GetSize（）< pPacket-> size）
返回S_FALSE ;,则检查数据包和缓冲区大小
; 
 
 //从数据包复制到样本缓冲区
 memcpy（pBuffer，pPacket-> data，pPacket-> size）; 
 
 //设置媒体采样时间
 REFERENCE_TIME start = m_mediaFile.timeStampToReferenceTime（pPacket-> pts）; 
 REFERENCE_TIME持续时间= m_mediaFile.timeStampToReferenceTime（pPacket-> duration）; 
 REFERENCE_TIME结束=开始+持续时间； 
 pSamp-> SetTime（& start，& end）; 
 pSamp-> SetMediaTime（& start，& end）; 
  

P.S。我已经使用hax264解码器调试了过滤器，并且在调用libav弃用的函数img_convert（）时崩溃。

解决方案

AM_MEDIA_TYPE 应该包含适用于h264的正确MEDIASUBTYPE。

这些都是错误的：

pvi-> bmiHeader.biWidth = videoRect.right;

pvi-> bmiHeader.biHeight = videoRect.bottom;

由于以下原因，您应使用独立于rcSource / rcTarget的宽度/高度

  pvi-> bmiHeader可能是零。
 
 
  pvi-> bmiHeader .biBitCount = m_pFormatContext-> streams [m_streamNo]-> codec-> bits_per_raw_sample; //或此处应为bits_per_coded_sample 
  
 
 
仅当 biWidth * biHeight * biBitCount / 8 是样本的真实大小。我不这么认为... 
 
 
  pvi-> bmiHeader.biCompression = FOURCC_H264; 
  
 
 
这也必须在子类型参数的AM_MEDIA_TYPE中传递。
 
 
 pvi-> bmiHeader.biSizeImage = GetBitmapSize（& pvi-> bmiHeader）; 
 
 
这失败了，因为该函数不知道fourcc，并且由于不是全帧，因此该示例的位计数显然是错误的。
 
 
您必须看看如何数据流由下游的h264过滤器处理。这似乎是有缺陷的。
 
I have searched and have found almost nothing, so I would really appreciate some help with my question.

I am writting a DirectShow source filter which uses libav to read and send downstream h264 packets from youtube's FLV file. But I can't find appropriate libav structure's fields to implement correctly filter's GetMediType() and FillBuffer(). Some libav fields is null. In consequence h264 decoder crashes in attempt to process received data.

Where am I wrong? In working with libav or with DirectShow interfaces? Maybe h264 requires additional processing when working with libav or I fill reference time incorrectly? Does someone have any links useful for writing DirectShow h264 source filter with libav?

Part of GetMediaType():
VIDEOINFOHEADER *pvi = (VIDEOINFOHEADER*) toMediaType->AllocFormatBuffer(sizeof(VIDEOINFOHEADER));
pvi->AvgTimePerFrame = UNITS_PER_SECOND / m_pFormatContext->streams[m_streamNo]->codec->sample_rate; //sample_rate is 0
pvi->dwBitRate       = m_pFormatContext->bit_rate;
pvi->rcSource        = videoRect;
pvi->rcTarget        = videoRect;

//Bitmap
pvi->bmiHeader.biSize     = sizeof(BITMAPINFOHEADER);
pvi->bmiHeader.biWidth    = videoRect.right;
pvi->bmiHeader.biHeight   = videoRect.bottom;
pvi->bmiHeader.biPlanes   = 1;
pvi->bmiHeader.biBitCount = m_pFormatContext->streams[m_streamNo]->codec->bits_per_raw_sample;//or should here be bits_per_coded_sample
pvi->bmiHeader.biCompression = FOURCC_H264;
pvi->bmiHeader.biSizeImage = GetBitmapSize(&pvi->bmiHeader);
Part of FillBuffer():
//Get buffer pointer
BYTE* pBuffer = NULL;
if (pSamp->GetPointer(&pBuffer) < 0)
   return S_FALSE;

//Get next packet
AVPacket* pPacket = m_mediaFile.getNextPacket();
if (pPacket->data == NULL)
   return S_FALSE;

//Check packet and buffer size
if (pSamp->GetSize() < pPacket->size)
   return S_FALSE;

//Copy from packet to sample buffer
memcpy(pBuffer, pPacket->data, pPacket->size);

//Set media sample time
REFERENCE_TIME start    = m_mediaFile.timeStampToReferenceTime(pPacket->pts);
REFERENCE_TIME duration = m_mediaFile.timeStampToReferenceTime(pPacket->duration);
REFERENCE_TIME end      = start + duration;
pSamp->SetTime(&start, &end);
pSamp->SetMediaTime(&start, &end);
P.S. I've debugged my filter with hax264 decoder and it crashes on call to libav deprecated function img_convert().
解决方案
You have to fill the right fields with the right values.
The AM_MEDIA_TYPE should contain the right MEDIASUBTYPE for h264.
And these are plain wrong :

pvi->bmiHeader.biWidth    = videoRect.right;
pvi->bmiHeader.biHeight   = videoRect.bottom;
You should use a width/height which is independent of the rcSource/rcTarget, due to the them being indicators, and maybe completely zero if you take them from some other filter.

pvi->bmiHeader.biBitCount = m_pFormatContext->streams[m_streamNo]->codec->bits_per_raw_sample;//or should here be bits_per_coded_sample

This only makes sense if biWidth*biHeight*biBitCount/8 are the true size of the sample. I do not think so ...

pvi->bmiHeader.biCompression = FOURCC_H264;

This must also be passed in the AM_MEDIA_TYPE in the subtype parameter.

pvi->bmiHeader.biSizeImage = GetBitmapSize(&pvi->bmiHeader);
This fails, because the fourcc is unknown to the function and the bitcount is plain wrong for this sample, due to not being a full frame.
You have to take a look at how the data stream is handled by the downstream h264 filter. This seems to be flawed.

                        
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