Method for regenerating the original data of a digitally coded video film, and apparatus for carrying out the method

Abstract

A method for regenerating the original data of a digitally coded video film is described, in which a specific picture type of a number of picture types (I, B, P) has been allocated to each of the individual pictures during coding and the coding order (DEO) does not correspond, at least in part, to the display order (DIO). This method provides for an independent time base to be used in order to recover the display order, which time base is obtained from internal information items in the decoder, the information items having been stored during the preceding decoding of a number of pictures. This method has the advantage that even with the omission of a header of a Group of Pictures (GOPH), the correct display order can still be achieved, even if the otherwise customary temporal reference codes in the bit stream signal an incorrect display order. An apparatus for carrying out the method is furthermore proposed.

Description

[0001] The invention relates to a method for regenerating the original data of a digitally coded video film and an apparatus for carrying out the method.PRIOR ART[0002] The invention is based on a method for regenerating the original data of a digitally coded video film of the generic type of the independent Claim 1. Apparatuses of this type have recently become known for example as a result of the commercially available DVD (Digital Versatile Disk) playback devices. These devices are designed in accordance with the so-called DVD Standard (Version 1.0). In this standard, reference is made to the so-called MPEG standards MPEG1 and MPEG2 with regard to the reproduction of video films. The MPEG2 standard is also known under the reference ISO / IEC 13818: 1994 "Information technology--generic coding of moving pictures and associated audio". The MPEG1 standard is also known under the designation ISO / IEC 11172: 1993 "Information Technology--coding of moving pictures and associated audio for...

AI Technical Summary

Benefits of technology

[0006] The object of the invention is to prevent in particular the undesirable scrambling of the display order after an omission of a GOP header.

[0009] Claim 3 specifies an advantageous measure which can advantageously be used particularly when, in the coding operation, variable sequences of picture types are permitted and a defined sequence of picture types for the pictures to be coded does not have to be rigidly complied with.

[0011] For an apparatus for carrying out the method according to the invention, it is very advantageous if a table is stored in which the information items for recovering the display order are stored for a number of decoded pictures and which is evaluated by a control unit in order to ensure the independent time base. Such a table can also be realized in a simple manner by software, with the result that the circuitry outlay remains low.

[0012] The measures in Claims 6 to 8 are likewise advantageous since, using the counter readings of the claimed counters, it is easy to ascertain which type of picture a preceding picture was. Since the counter readings are a matter of simple numerical values, these can easily be compared with one another in order rapidly to obtain the picture type. This information combined with the information regarding whether or not the picture has already been released for display easily permit, given a joint consideration of a plurality of preceding pictures, a conclusion to be drawn regarding which picture must subsequently be released for display. According to Claim 11, the size of the table is advantageously adapted such that the picture sequence having the largest number of successive B pictures, including the I or P pictures adjoining these B pictures, can still just be called up in the table.

Problems solved by technology

Today's DVD playback devices encounter the problem that they cannot always operate without any errors in everyday operation, one of the reasons being that on account of the drastic increase in the storage density on the DVD itself, error-free reading cannot be effected in every situation.

Slight scratches as well as dust and grease spots can then very easily prevent satisfactory reading of information.

The nature of the recording means that even when the scratch / spot is relatively small, relatively large areas may be affected on account of the high storage density, and are not correctly evaluated.

This results in poor picture and sound quality from time to time, despite error concealment measures that are present.

A problem arises whenever, on account of an error, a GOP header is omitted and suddenly pictures of another Group are decoded which have a smaller temporal reference code than pictures that have already been decoded and are located in a memory.

This, of course, leads to an incorrect display of the pictures, which is clearly discernible to the viewer.

This leads to undesirable "jitter" of the picture, which is extremely disturbing.

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