GF_Err gf_isom_change_generic_sample_description(GF_ISOFile *movie, u32 trackNumber, u32 StreamDescriptionIndex, GF_GenericSampleDescription *udesc)
{
	GF_TrackBox *trak;
	GF_Err e;
	GF_GenericVisualSampleEntryBox *entry;

	e = CanAccessMovie(movie, GF_ISOM_OPEN_WRITE);
	if (e) return e;

	trak = gf_isom_get_track_from_file(movie, trackNumber);
	if (!trak || !trak->Media || !StreamDescriptionIndex) return GF_BAD_PARAM;

	entry = (GF_GenericVisualSampleEntryBox *)gf_list_get(trak->Media->information->sampleTable->SampleDescription->child_boxes, StreamDescriptionIndex-1);
	if (!entry) return GF_BAD_PARAM;
	if (entry->type == GF_ISOM_BOX_TYPE_GNRV) {
		entry->vendor = udesc->vendor_code;
		entry->version = udesc->version;
		entry->revision = udesc->revision;
		entry->temporal_quality = udesc->temporal_quality;
		entry->spatial_quality = udesc->spatial_quality;
		entry->Width = udesc->width;
		entry->Height = udesc->height;
		strcpy(entry->compressor_name, udesc->compressor_name);
		entry->color_table_index = -1;
		entry->frames_per_sample = 1;
		entry->horiz_res = udesc->h_res ? udesc->h_res : 0x00480000;
		entry->vert_res = udesc->v_res ? udesc->v_res : 0x00480000;
		entry->bit_depth = udesc->depth ? udesc->depth : 0x18;
		if (entry->data) gf_free(entry->data);
		entry->data = NULL;
		entry->data_size = 0;
		if (udesc->extension_buf && udesc->extension_buf_size) {
			entry->data = (char*)gf_malloc(sizeof(char) * udesc->extension_buf_size);
			if (!entry->data) {
				gf_isom_box_del((GF_Box *) entry);
				return GF_OUT_OF_MEM;
			}
			memcpy(entry->data, udesc->extension_buf, udesc->extension_buf_size);
			entry->data_size = udesc->extension_buf_size;
		}
		return GF_OK;
	} else if (entry->type == GF_ISOM_BOX_TYPE_GNRA) {
		GF_GenericAudioSampleEntryBox *gena = (GF_GenericAudioSampleEntryBox *)entry;
		gena->vendor = udesc->vendor_code;
		gena->version = udesc->version;
		gena->revision = udesc->revision;
		gena->bitspersample = udesc->bits_per_sample ? udesc->bits_per_sample : 16;
		gena->channel_count = udesc->nb_channels ? udesc->nb_channels : 2;
		gena->samplerate_hi = udesc->samplerate;
		gena->samplerate_lo = 0;
		if (gena->data) gf_free(gena->data);
		gena->data = NULL;
		gena->data_size = 0;

		if (udesc->extension_buf && udesc->extension_buf_size) {
			gena->data = (char*)gf_malloc(sizeof(char) * udesc->extension_buf_size);
			if (!gena->data) {
				gf_isom_box_del((GF_Box *) gena);
				return GF_OUT_OF_MEM;
			}
			memcpy(gena->data, udesc->extension_buf, udesc->extension_buf_size);
			gena->data_size = udesc->extension_buf_size;
		}
		return GF_OK;
	} else if (entry->type == GF_ISOM_BOX_TYPE_GNRM) {
		GF_GenericSampleEntryBox *genm = (GF_GenericSampleEntryBox *)entry;
		if (genm->data) gf_free(genm->data);
		genm->data = NULL;
		genm->data_size = 0;

		if (udesc->extension_buf && udesc->extension_buf_size) {
			genm->data = (char*)gf_malloc(sizeof(char) * udesc->extension_buf_size);
			if (!genm->data) {
				gf_isom_box_del((GF_Box *) genm);
				return GF_OUT_OF_MEM;
			}
			memcpy(genm->data, udesc->extension_buf, udesc->extension_buf_size);
			genm->data_size = udesc->extension_buf_size;
		}
		return GF_OK;
	}
	return GF_BAD_PARAM;
}