Method for recording data, method for retrieving sets of data, data file, data structure and medium carrying such data
View Patent ↗After recording a data container, a back-pointer item is recorded, comprising a specific key and an indicator of the length of the data container. This back-pointer item can be used to jump to the beginning of the data container when reading the file backwards. Other types of coding than KLV coding are also proposed. These types of coding can be used for instance to code the back-pointer item.
1. Method for recording encapsulated data on a medium in a recording order, which can be retrieved in an order opposite to the recording order, said method being implemented on a video recorder and comprising the steps of:
recording on the medium in a recording order, using said video recorder, as a data container, a KLV coded item which comprises a first key indicating type of the encapsulated data, a first length indicator of the length of the encapsulated data, and the encapsulated data;
recording on the medium in a recording order using said video recorder following the KLV coded item as a relative pointer to the beginning of the preceding data container, a back-pointer KLV coded item having a back pointer length and comprising a second key indicating other encapsulated data being of a back pointer type and a second length indicator of the length of the other encapsulated data and having as the other encapsulated data, a length value of the KLV coded item or a cumulated length value of said length of the KLV coded item and the back pointer length;
repeating the recording steps.
2. Method according to claim 1 , further comprising:
re-recording the second length indicator after the back pointer KLV coded item.
3. Method according to claim 2 , further comprising:
re-recording the second key after the second length indicator.
4. Method for retrieving on a video player a KLV coded item, which was recorded according to claim 1 , having a KLV item length on a medium in an order opposite to the recording order from a currently accessed KLV item, said method comprising the steps of:
accessing, using said video player, the second key indicating encapsulated data as being of a back pointer type, and wherein the encapsulated data has a fixed length;
reading, using said video player, the other encapsulated data indicating the cumulated length of said KLV item length and said back pointer length; and
accessing, using said video player, the KLV item by jumping a number of bytes further backwards wherein the number of bytes equals said cumulated length value.
5. Method for retrieving on a video player a KLV coded item, which was recorded according to claim 1 , having a KLV item length on a medium, in an order opposite to the recording order from a currently accessed KLV item, the method comprising the steps of:
accessing, using said video player, the second key indicating encapsulated data as being of a back-pointer type, and wherein the encapsulated data has a non-fixed length;
reading, using said video player, the second length indicator of the length of the encapsulated data prior to reading the value;
reading, using said video player, the other encapsulated data indicating the cumulated length of said KLV item length and said back pointer length; and
accessing, using said video player, the KLV item by jumping a number of bytes further backwards wherein the number of bytes equals said cumulated length value.