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Apparatus and method for converting a compressed video stream with preview of converted stream

Apparatus and method for converting a compressed video stream with preview of converted stream description/claims

This is a continuation application of U.S. patent application Ser. No. 10/441,012, filed on May 20, 2003, now allowed, the contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to an apparatus for converting an encoding system of video stream or video transcoder, a method therefor, and a video recording/reproducing device using the above apparatus.

2. Description of the Related Art

Technologies for digitizing image information and compression encoding by an MPEG video compression technology to store on a storage medium or to transmit through a communication medium have been used for various types of equipment. Such examples are a DVD recording/reproducing device using an MPEG-2 Video (ISO/IEC13818-2) system, communications between portable terminals using an MPEG-4 Video (ISO/IEC14496-2) system, and the like. Because the compression systems are different depending on uses, each device needs to convert data between different compression encoding systems.

To meet the above necessity, there is a device for transcoding the video stream compression coded by the MPEG-2 method into another compression encoding system. At that time, a user desires to check the image quality of the transcoded stream to select a compression parameter for transcoding. And, a technology therefor has been proposed (e.g., refer to JP-A-2001-36844).

JP-A-2001-36844 discloses to output the stream before transcoding and the stream after transcoding simultaneously, decodes them and outputs the decoded images at the same time. The user checks the images for a difference in image quality between them to select desired image quality. Such a system reproduces the entire stream before the conversion and also operates to check the image quality of the converted stream. Therefore, it is hard to set the image quality of a short stream portion in detail. For example, when the image quality of a relatively short stream such as moving image mail is to be determined, reproduction of the relevant portion ends so soon that it is difficult to conduct the setting work.

There is also a demand for falling of a transmission time of the converted video stream within a designated value when the converted data is sent through a network. There is also a demand for adjustment of a frame rate and an amount of codes allotted to the frame as the image quality of each frame. When a bit rate is fixed, the frame rate and the allotted code amount of each frame are in a contrary relationship, so that they must be set while being kept in balance. Users have demanded to make such detail setting interactively. But, the JP-A-2001-36844 has not fully considered such ease of use.

In view of the situations described above, the present invention provides a video transcoder by which a user can easily set a parameter at the time of conversion, a method for video transcoder, and a video recording/reproducing device using it.

To achieve the object, the apparatus according to an aspect of the present invention comprises a reproducer means reproducing a first video stream recorded on a storage medium; a stream converter converting the reproduced first video stream into a second video stream; a conversion period designation means designating a conversion period in the first video stream; a stream output unit outputting the converted second video stream; and a preview output unit outputting an image corresponding to a decoded image of the converted second video stream to a display device. The above stream output unit outputs the second video stream for a period designated by the conversion period designator.

Especially, the reproducer repeatedly reproduces the first video stream for the period designated by the conversion period designator, and the preview output unit repeatedly outputs an image corresponding to the decoded image of the period designated by the conversion period designator.

The apparatus according to another aspect of the present invention comprises a stream converter converting the first video stream into the second video stream; a stream output unit outputting the converted second video stream; and a preview output unit outputting an image corresponding to a decoded image of the converted second video stream to a display device. The stream converter generates a local decode image of the second video stream for frame-to-frame motion compensation; and the preview output unit outputs a local decode image generated by the stream converter as an image corresponding to the decoded image of the second video stream.

The apparatus according to the other aspect of the present invention further comprises a parameter setting unit setting a parameter related to the conversion by the stream converter, wherein the stream output unit starts outputting the second video stream after setting of a parameter of the stream converter by the parameter setting unit.

Accordingly, the user can readily set a parameter at the time of conversion by checking the preview screen.

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