os->lastpts = os->lastdts = theora_gptopts(s, idx, os->granule, NULL) - duration;
if(s->streams[idx]->start_time == AV_NOPTS_VALUE) {
s->streams[idx]->start_time = os->lastpts;
os->lastpts = os->lastdts = theora_gptopts(s, idx, os->granule, NULL) - duration;
if(s->streams[idx]->start_time == AV_NOPTS_VALUE) {
s->streams[idx]->start_time = os->lastpts;