GF_BitRateBox *gf_isom_sample_entry_get_bitrate(GF_SampleEntryBox *ent, Bool create)
{
	u32 i=0;
	GF_BitRateBox *a;
	while ((a = (GF_BitRateBox *)gf_list_enum(ent->child_boxes, &i))) {
		if (a->type==GF_ISOM_BOX_TYPE_BTRT) return a;
	}
	if (!create) return NULL;
	a = (GF_BitRateBox *) gf_isom_box_new_parent(&ent->child_boxes, GF_ISOM_BOX_TYPE_BTRT);
	return a;
}
GF_BitRateBox *gf_isom_sample_entry_get_bitrate(GF_SampleEntryBox *ent, Bool create)
{
	u32 i=0;
	GF_BitRateBox *a;
	while ((a = (GF_BitRateBox *)gf_list_enum(ent->child_boxes, &i))) {
		if (a->type==GF_ISOM_BOX_TYPE_BTRT) return a;
	}
	if (!create) return NULL;
	a = (GF_BitRateBox *) gf_isom_box_new_parent(&ent->child_boxes, GF_ISOM_BOX_TYPE_BTRT);
	return a;
}