The introduction of HDTV and the availability of high-definition source material has resulted in the release of video files that exceed the maximum allowed resolution by the TDX rules, which anticipated DVD-Video rips as the ultimate source. Due to a missing standard these releases follow different rules. They are usually tagged as HR HDTV and use half the resolution of 1080i (960 × 540 px, vertically cropped to 528 or 544 px). Some releases also use a resolution of 1024 × 576 px to provide a proper aspect ratio of 16:9. Occasionally, shows (usually animated shows) aired in Standard Definition (PDTV) are often uploaded as HR (high resolution) PDTV using the H264 codec which offers much better compression than XviD, allowing a higher resolution in a file the same size as an XviD encoded video using a Standard Definition source.