GF_Err gf_isom_rewrite_text_sample(GF_ISOSample *samp, u32 sampleDescriptionIndex, u32 sample_dur)
{
	GF_BitStream *bs;
	u32 pay_start, txt_size;
	Bool is_utf_16 = 0;
	if (!samp || !samp->data || !samp->dataLength) return GF_OK;

	bs = gf_bs_new(samp->data, samp->dataLength, GF_BITSTREAM_READ);
	txt_size = gf_bs_read_u16(bs);
	gf_bs_del(bs);

	/*remove BOM*/
	pay_start = 2;
	if (txt_size>2) {
		/*seems 3GP only accepts BE UTF-16 (no LE, no UTF32)*/
		if (((u8) samp->data[2]==(u8) 0xFE) && ((u8)samp->data[3]==(u8) 0xFF)) {
			is_utf_16 = 1;
			pay_start = 4;
			txt_size -= 2;
		}
	}

	/*rewrite as TTU(1)*/
	bs = gf_bs_new(NULL, 0, GF_BITSTREAM_WRITE);
	gf_bs_write_int(bs, is_utf_16, 1);
	gf_bs_write_int(bs, 0, 4);
	gf_bs_write_int(bs, 1, 3);
	gf_bs_write_u16(bs, 8 + samp->dataLength - pay_start);
	gf_bs_write_u8(bs, sampleDescriptionIndex + SAMPLE_INDEX_OFFSET);
	gf_bs_write_u24(bs, sample_dur);
	/*write text size*/
	gf_bs_write_u16(bs, txt_size);
	if (txt_size) gf_bs_write_data(bs, samp->data + pay_start, samp->dataLength - pay_start);

	gf_free(samp->data);
	samp->data = NULL;
	gf_bs_get_content(bs, &samp->data, &samp->dataLength);
	gf_bs_del(bs);
	return GF_OK;
}
GF_Err gf_isom_rewrite_text_sample(GF_ISOSample *samp, u32 sampleDescriptionIndex, u32 sample_dur)
{
	GF_BitStream *bs;
	u32 pay_start, txt_size;
	Bool is_utf_16 = 0;
	if (!samp || !samp->data || !samp->dataLength) return GF_OK;

	bs = gf_bs_new(samp->data, samp->dataLength, GF_BITSTREAM_READ);
	txt_size = gf_bs_read_u16(bs);
	gf_bs_del(bs);

	 
	pay_start = 2;
	if (txt_size>2) {
		 
		if (((u8) samp->data[2]==(u8) 0xFE) && ((u8)samp->data[3]==(u8) 0xFF)) {
			is_utf_16 = 1;
			pay_start = 4;
			txt_size -= 2;
		}
	}

	 
	bs = gf_bs_new(NULL, 0, GF_BITSTREAM_WRITE);
	gf_bs_write_int(bs, is_utf_16, 1);
	gf_bs_write_int(bs, 0, 4);
	gf_bs_write_int(bs, 1, 3);
	gf_bs_write_u16(bs, 8 + samp->dataLength - pay_start);
	gf_bs_write_u8(bs, sampleDescriptionIndex + SAMPLE_INDEX_OFFSET);
	gf_bs_write_u24(bs, sample_dur);
	 
	gf_bs_write_u16(bs, txt_size);
	if (txt_size) gf_bs_write_data(bs, samp->data + pay_start, samp->dataLength - pay_start);

	gf_free(samp->data);
	samp->data = NULL;
	gf_bs_get_content(bs, &samp->data, &samp->dataLength);
	gf_bs_del(bs);
	return GF_OK;
}