Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Patent
1997-03-21
1998-02-10
Faile, Andrew
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
386 54, 386111, H04N 576
Patent
active
057178151
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a compression data editing apparatus such that audio data which was data compressed is reproduced on a video frame or field unit basis and, more particularly, to a compression data editing apparatus which can smoothly reproduce without noises at a switching point (editing point) by applying a cross fading when switched (edited) data is reproduced.
BACKGROUND ART
An audio video recording and reproducing apparatus such as to record and reproduce compressed video data and audio data has been put into practical use. In such an apparatus, when an audio signal which was sampled at a sampling frequency of 48 kHz is encoded by the MPEG (Layer I), a block train of a sampling length of 384 is formed. The number of samples of the audio data corresponding to one frame of an NTSC image is equal to 1601 or 1602.
As mentioned above, according to the encoding in which the sample length of 384 is set to a unit encoding block, since the number of encoded blocks in one frame is not equal to an integer number, in order to form a signal train synchronized with the frame, it is necessary to divide the encoded block in the middle of the process. When such a code is switched (edited) on a frame unit basis and is decoded after that, the blocks before and after the switching point (editing point) enter a state in which the data is partially dropped out. In the worst case, namely, when each of the blocks before and after the frame boundary has 383 samples, the data is incomplete in an interval of 766 samples and the intervals each having 256 samples before and after such an interval cannot be decoded.
Therefore, in such an audio video recording and reproducing apparatus, a system such that a ratio between a block period of time as a processing unit of compression audio data and a video frame period of time doesn't show an integer relation has been proposed. FIG. 17B shows a constructional example of an encoding apparatus 100 of such a system. FIG. 18 shows a constructional example of a decoding apparatus 200.
In FIG. 17, an audio signal 101 is a digital signal which was sampled at 48 kHz. A sampling period of 20.8 .mu.sec is set to T hereinafter. The audio signal 101 is supplied to an audio signal input terminal of an MPEG encoding circuit 105 for performing an encoding of the MPEG Layer I.
A block pulse 102 is a pulse signal which is activated every 384T and is supplied to both of one input terminal of the MPEG encoding circuit 105 and one input terminal of a phase comparing circuit 106. An input frame pulse 103 is a pulse signal which is activated every period, namely, 1601T or 1602T in which a frame frequency of 29.97 Hz is synchronized with a sampling frequency of 48 kHz. The input frame pulse 103 is supplied to the other input terminal of the phase comparing circuit 106. A code frame pulse 104 is a signal indicative of an output phase of a code train 109 that is outputted on a frame unit basis from the encoding apparatus and is also a pulse signal which is activated every 1601T or 1602T. The code frame pulse 104 is supplied to a memory circuit 107.
In the encoding apparatus 100, the audio signal 101 supplied to the MPEG encoding apparatus 105 is converted into an MPEG code train and is sequentially written into the memory circuit 107. The block pulse 102 and input frame pulse 103 supplied to the phase comparator 106 are phase compared. Information indicative of a head audio encoded block of each frame unit and information indicative of an offset amount (phase difference) from the frame boundary of the head block are outputted. The information indicative of the head block of the frame is written into the memory circuit 107. The information indicative of the offset amount is supplied to an offset adding circuit 108.
The input audio signal 101 supplied to the MPEG encoding circuit 105 is encoding processed on a block unit basis at a timing of the block pulse 102 which is supplied together with the signal 101. The processed signal is outputted as a code train 109 through the memory circu
REFERENCES:
patent: 4644400 (1987-02-01), Kouyama et al.
patent: 5386581 (1995-01-01), Suzuki et al.
patent: 5557423 (1996-09-01), Phillip et al.
Mori Masahito
Nakano Hiroshi
Sasaki Masao
Takagi Satoshi
Boccio Vincent F.
Faile Andrew
Frommer William S.
Sinderbrand Alvin
Sony Corporation
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