Hoe to transcode vorbis stream from MKV container to OGG container Options

[SZhang]

Hi,
I have a question while I try to implement a transcoder which can chage the vorbis container from MKV to OGG. According to the specification of OGG, the granule position of a page represents the end PCM sample position of the last packet completed on that page. I don't want to get the sample position by decoding vorbis stream, so I use the timecode and sample rate in MKV to generate sample position. If the duration information is not coded in MKV header, I don't know how to calculate the granule position for the last page of the stream. Could help to give some suggestion on this issue? Thanks in advance!