Apparatus for a synchronized playback of audio-video signals

• US 6,078,725 A
• Filed: 01/07/1998
• Issued: 06/20/2000
• Est. Priority Date: 01/09/1997
• Status: Expired due to Term

• Current Assignee: NEC Personal Computers, Ltd. (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Tanaka, Mitsumasa
• Primary Examiner(s): Kostak, Victor R.
• Application Number:
  US09/003,754
• Time in Patent Office: 895 Days
• Field of Search: 348/515, 348/518, 348/423, 348/845, 386/54, 386/100, 386/101, 386/104, 386/109-112
• US Class Current: 386/241
• CPC Class Codes: H04N 21/43072 of multiple content streams on the same device

Abstract

To provide an apparatus for a synchronized playback of com- pressed digital data of audio-video signals adequately even when there are data errors with a simple configuration to be applied to a system having comparatively low data processing ability, independent of resolution of a software timer of the system, the apparatus obtains a reference time indicating production time passage of the audio signal component from reproduced data amount added with rejected error data amount of the audio signal component, and detects progress of the video signal component in reference to the reference time considering rejected error video data amount.

Claims

1. An apparatus for synchronized playback of audio-video signals representing an audio signal component and a video signal component in synchronization with each other by decompressing compressed digital data of the audio signal component and the video signal component, said apparatus comprising:

means for obtaining a reference time indicating a reproduction time passage of the audio signal component from a sum of a reproduced data amount of the audio signal component and an error data amount of said audio signal component rejected because of a data error, based upon header information of the compressed digital data, which includes a sampling rate of the audio signal component and a frame rate of the video signal component; and

means for detecting a progress of the video signal component by comparing said reference time to a real frame number of the video signal component, said real frame number indicating a number of processed picture frames and rejected error picture frames.

2. The apparatus for synchronized playback of audio-video signals recited in claim 1, said means for detecting the progress of the video signal component having:

a video frame counter for counting and maintaining said real frame number by accumulating a number of picture frames actually decompressed and a number of picture frames omitted from being decompressed;

a video error detector for adding an error frame number of the video signal component, which corresponds to a number of picture frames rejected without reproduction because of a data error, to said real frame number; and

a delay detector for calculating an ideal frame number of the video signal component to be displayed according to said reference time and said frame rate, and detecting said progress of the video signal component by comparing said real frame number to said ideal frame number.

3. The apparatus for synchronized playback of audio-video signals recited in claim 1, further comprising means for restoring a difference in display timing between the video signal component and said reference time by performing frame omission and delaying decompression of the video signal component according to said progress of the video signal component.

4. The apparatus for synchronized playback of audio-video signals recited in claim 3;

wherein said frame omission is performed according to an order of priority attributed to frames of the video signal component subject to said frame omission in connection with kinds of compressed data of said frames.

5. The apparatus for synchronized playback of audio-video signals recited in claim 3;

wherein said decompression delay is performed by controlling decompression of compressed data of a frame of the video signal component be delayed until said difference of display timing of said frame from said reference time becomes within a threshold value.

6. A method for synchronizing playback of audio-video signals representing an audio signal component and a video signal component in synchronization with each other by decompressing compressed digital data of the audio signal component and the video signal component, comprising:

obtaining a reference time indicating a reproduction time passage of the audio signal component from a sum of a reproduced data amount of the audio signal component and an error data amount of said audio signal component rejected because of a data error, based upon header information of the compressed digital data, which includes a sampling rate of the audio signal component and a frame rate of the video signal component; and

detecting a progress of the video signal component by comparing said reference time to a real frame number of the video signal component, said real frame number indicating a number of processed picture frames and rejected error picture frames.