private static void CheckAudioFormat(IMFMediaType mediaType, IDictionary<FormatCheckElement, Tuple<bool, object>> ret)
{
var subType = mediaType.GetSubType();
var isAac = subType == MFMediaType.AAC;
ret.Add(FormatCheckElement.AudioCodec, Tuple.Create<bool, object>(isAac, subType));
if (isAac)
{
var aacObjectType = mediaType.GetAacObjectType();
ret.Add(FormatCheckElement.AudioAacObjectType, Tuple.Create<bool, object>(aacObjectType == 2, aacObjectType));
var channels = mediaType.GetChannel();
ret.Add(FormatCheckElement.AudioChannel, Tuple.Create<bool, object>(channels == 1 || channels == 2, channels));
}
}