// Linearly interpolate the value for a given key in the map. If the
// key is outside the range of keys in the map, linearly extrapolate
// using the fallback ratio.
uint64_t DecoderBase::TranslatePosition(const frm_pos_map_t &map,
long long key,
float fallback_ratio)
{
uint64_t key1, key2;
uint64_t val1, val2;
frm_pos_map_t::const_iterator lower = map.lowerBound(key);
// QMap::lowerBound() finds a key >= the given key. We want one
// <= the given key, so back up one element upon > condition.
if (lower != map.begin() && (lower == map.end() || lower.key() > key))
--lower;
if (lower == map.end() || lower.key() > key)
{
key1 = 0;
val1 = 0;
LOG(VB_PLAYBACK, LOG_DEBUG, LOC +
QString("TranslatePosition(key=%1): extrapolating to (0,0)")
.arg(key));
}
else
{
key1 = lower.key();
val1 = lower.value();
}
// Find the next key >= the given key. QMap::lowerBound() is
// precisely correct in this case.
frm_pos_map_t::const_iterator upper = map.lowerBound(key);
if (upper == map.end())
{
// Extrapolate from (key1,val1) based on fallback_ratio
key2 = key;
val2 = val1 + fallback_ratio * (key2 - key1) + 0.5;
LOG(VB_PLAYBACK, LOG_DEBUG, LOC +
QString("TranslatePosition(key=%1, ratio=%2): "
"extrapolating to (%3,%4)")
.arg(key).arg(fallback_ratio).arg(key2).arg(val2));
return val2;
}
else
{
key2 = upper.key();
val2 = upper.value();
}
if (key1 == key2) // this happens for an exact keyframe match
return val2; // can also set key2 = key1 + 1 avoid dividing by zero
return val1 + (double) (key - key1) * (val2 - val1) / (key2 - key1) + 0.5;
}
static void UpdatePositionMap(frm_pos_map_t &posMap, QString mapfile,
ProgramInfo *pginfo)
{
if (pginfo && mapfile.isEmpty())
{
pginfo->ClearPositionMap(MARK_KEYFRAME);
pginfo->ClearPositionMap(MARK_GOP_START);
pginfo->SavePositionMap(posMap, MARK_GOP_BYFRAME);
}
else if (!mapfile.isEmpty())
{
FILE *mapfh = fopen(mapfile.toLocal8Bit().constData(), "w");
if (!mapfh)
{
LOG(VB_GENERAL, LOG_ERR, QString("Could not open map file '%1'")
.arg(mapfile) + ENO);
return;
}
frm_pos_map_t::const_iterator it;
fprintf (mapfh, "Type: %d\n", MARK_GOP_BYFRAME);
for (it = posMap.begin(); it != posMap.end(); ++it)
fprintf(mapfh, "%lld %lld\n",
(unsigned long long)it.key(), (unsigned long long)*it);
fclose(mapfh);
}
}