ffmpeg Reading Media Reading from an IStream in a IOContext
Example
The API call avio_alloc_context, which sets up a custom IO context, takes in a pointer to a Read function. If you are reading from an IStream, you can use the following:
/**
* Reads from an IStream into FFmpeg.
*
* @param ptr A pointer to the user-defined IO data structure.
* @param buf A buffer to read into.
* @param buf_size The size of the buffer buff.
*
* @return The number of bytes read into the buffer.
*/
int FileStreamRead(void* ptr, uint8_t* buf, int buf_size)
{
// This is your IStream
IStream* stream = reinterpret_cast<IStream*>(ptr);
ULONG bytesRead = 0;
HRESULT hr = stream->Read(buf, buf_size, &bytesRead);
if(hr == S_FALSE)
return AVERROR_EOF; // End of file
if(FAILED(hr))
return -1;
return bytesRead;
}
