write_chunk_hdr(&mut self.bw, str.get_media_type(), str_num as u32)?;
self.bw.write_u32le(chunk_len)?;
self.bw.write_buf(pkt.get_buffer().as_slice())?;
write_chunk_hdr(&mut self.bw, str.get_media_type(), str_num as u32)?;
self.bw.write_u32le(chunk_len)?;
self.bw.write_buf(pkt.get_buffer().as_slice())?;