Digital broadcast sending apparatus, receiving apparatus and digital broadcast system

• US 20060083315A1
• Filed: 10/14/2005
• Published: 04/20/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Uchiyama, Hiroki, Tomobe, Osamu, Ishida, Takaharu, Sato, Yoshihito
• Granted Patent: US 7,580,612 B2
• Time in Patent Office: Days
• US Class Current: 375/240.250
• CPC Class Codes: H04H 60/12 wherein another information is substituted for the portion of broadcast information
• CPC Class Codes: H04N 17/004 for digital television systems
• CPC Class Codes: H04N 21/234327 by decomposing into layers, e.g. base layer and one or more enhancement layers
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer
• CPC Class Codes: H04N 21/440263 by altering the spatial resolution, e.g. for displaying on a connected PDA

Abstract

In the digital broadcast to a mobile unit, the continuous reproduction of an image cannot be guaranteed when switching the hierarchical level in accordance with the receiving condition of the radio wave and therefore the viewer has a sense of discomfort. A digital broadcast sending apparatus sends out by encoding a plurality of simultaneous broadcast streams in the same sync signal generator. A switching determination unit of the receiving apparatus switches the plurality of simultaneous broadcast streams in accordance with the receiving condition (weak hierarchical level/strong hierarchical level), and a sync adjustment unit continuously displays an image without interruptions based on the received sync signal. At the time of this switching operation, one stream is gradually switched to the other.

Claims

1. A digital broadcast receiving apparatus having a video display unit for displaying an image by receiving a multiplexed broadcast signal including a high-quality first video code and a second video code generated from the same video content and each including a sync signal, comprising:

a demultiplex processing unit for demultiplexing the data multiplexed on the broadcast signal;

a first decoder for restoring the first video code and the sync signal thereof;

a second decoder for restoring the second video code and the sync signal thereof;

a first buffer for holding the decoded high-quality video signal;

a second buffer for holding the decoded low-quality video signal;

an enlargement processing unit for recovering and enlarging the low-quality video signal from the second buffer;

a switching determination unit for monitoring the receiving condition of the high-quality video signal and determining whether the receiving condition is good condition or not; and

a sync adjustment unit for recovering the high-quality video signal from the first buffer in the case where the determination result of the switching determination unit is good condition, recovering the enlarged low-quality video signal from the enlargement processing unit in the case where the determination result is negative and outputting the video signal to the video display unit in accordance with the delayed one of the sync signals.

2. The digital broadcast receiving apparatus according to claim 1, wherein in switching between the high-quality video display and the low-quality video display, the sync adjustment unit switches the high-quality image to the low-quality image or the low-quality image to the high-quality image gradually during a predetermined time.

3. The digital broadcast receiving apparatus according to claim 2, wherein the first buffer and the second buffer hold the video frame image for at least the predetermined time,

wherein the sync adjustment synthesizes the video frame image held in the first buffer and the video frame image held in the second buffer at a predetermined synthesis ratio, and

wherein after the time point when the switching determination unit issues a switch instruction before the lapse of the predetermined time, the synthesis ratio is gradually changed for each frame display from the synthesis ratio as of the time point when the switching instruction is issued to the final synthesis ratio.

4. The digital broadcast receiving apparatus according to claim 3, wherein at the time of switching from the display of the high-quality image to the display of the low-quality image, the final synthesis ratio is set to 0 for the high-quality image and 1 for the low-quality image.

5. The digital broadcast receiving apparatus according to claim 3, wherein at the time of switching from the display of the low-quality image to the display of the high-quality image, the final synthesis ratio is set to 0 for the low-quality image and 1 for the high-quality image.

6. The digital broadcast receiving apparatus according to claim 3, wherein the synthesis process is executed in such a manner that in accordance with the number of pixels for the higher resolution, the weighted average is produced in accordance with the synthesis ratio for each pixel.

7. The digital broadcast receiving apparatus according to claim 3, wherein the MPEG2 encoding scheme is used for encoding the high-quality image and the MPEG4 encoding scheme for encoding the low-quality image, and

wherein the synthesis process is executed by adjusting the ratio by macro block.

8. The digital broadcast receiving apparatus according to claim 3, wherein the MPEG2 encoding scheme is used for encoding the high-quality image and the MPEG4 encoding scheme for encoding the low-quality image,

wherein the synthesis process uses the I picture of the MPEG code with the larger setting of the synthesis ratio, and

wherein in accordance with the synthesis ratio, the P picture or the B picture is decoded using the picture of the other MPEG code.

9. The digital broadcast receiving apparatus according to claim 8, wherein the I picture of MPEG code with the larger setting of the synthesis ratio is used, so that the P picture or the B picture is decoded by executing the synthesis process by macro block in accordance with the synthesis ratio.

11. The digital broadcast receiving apparatus according to claim 1, comprising a receiving accumulator,

wherein at least the first video code with the sync signal, the second video code with the sync signal and the determination signal indicating the determination information of the switching determination unit are accumulated in the receiving accumulator, and

wherein in the case of reproduction from the receiving accumulator after receiving, the first video code and the second video code reproduced from the receiving accumulator are switched using the determination signal.

10. (canceled)

12. A digital broadcast sending apparatus for sending a multiplexed broadcast signal including a high-quality first video code and a low-quality second video code generated from the same video content and each including a sync signal, comprising:

a sync signal generator for generating a sync signal;

a video distributor for distributing the video content;

a first video encoder for encoding one of the distributed video content in synchronism with the sync signal and generating the first video code and a sync code in synchronism with the first video code;

a second video encoder for encoding another one of the distributed video content in synchronism with the sync signal with a different quality than the first video encoder and generating the second video code and a sync code in synchronism with the video code;

a first delay unit for delaying the first video code and the first sync code;

a second delay unit for delaying the second video code and the second sync code; and

a multiplexer for multiplexing the first video code including the first sync code thereof and the second video code including the second sync code thereof with a time shift of not longer than a predetermined time.

15. The digital broadcast system according to claim 12, wherein the sending apparatus includes a sending communication unit and transmits a third video code and the sync signal through the sending communication unit,

wherein the receiving apparatus includes a receiving communication unit and transmits the third video code and the sync signal through the receiving communication unit, and

wherein in the case where the first video code becomes unreceivable upon determination of the switching determination unit, the first video code is switched to the second video code or the third video code.

13. A digital broadcast systems comprising:

a sending apparatus for sending out a broadcast signal by multiplexing a high-quality first video code and a low-quality second video code generated from the same video content, each containing a sync signal, and

a receiving apparatus for receiving the broadcast signal and displaying an image,

wherein the receiving apparatus has a video display unit for displaying an image by receiving the multiplexed broadcast signal, and includes

a demultiplex processing unit for demultiplexing the data multiplexed on the broadcast signal;

a first decoder for restoring the first video code and the sync signal thereof;

a second decoder for restoring the second video code and the sync signal thereof;

a first buffer for holding the decoded high-quality video signal;

a second buffer for holding the decoded low-quality video signal;

an enlargement processing unit for recovering and enlarging the low-quality video signal from the second buffer;

a switching determination unit for monitoring the receiving condition of the high-quality video signal and determining whether the receiving condition is good condition or not; and

a sync adjustment unit for recovering the high-quality video signal from the first buffer in the case where the determination result of the switching determination unit is good condition, recovering the enlarged low-quality video signal from the enlargement processing unit in the case where the determination result is negative and outputting the video signal to the video display unit in accordance with the delayed one of the sync signals;

wherein the sending apparatus includes

a sync signal generator for generating the sync signal;

a video distributor for distributing the video content;

a first video encoder for encoding one of the distributed video content in synchronism with the sync signal and generating the first video code and a sync code in synchronism with the first video code;

a second video encoder for encoding another one of the distributed video content in synchronism with the sync signal with a different quality than the first video encoder and generating the second video code and a sync code in synchronism with the video code;

a first delay unit for delaying the first video code and the first sync code;

a second delay unit for delaying the second video code and the second sync code; and

a multiplexer for multiplexing the first video code including the first sync code thereof and the second video code including the second sync code thereof with a time shift of not longer than a predetermined time.

14. The digital broadcast system according to claim 13, wherein the sending apparatus includes a sending accumulator for accumulating the first video code and the sync signal, and the sending accumulator outputs the first video code and the sync signal delayed by a predetermined time to the multiplexer, and

wherein the receiving apparatus includes a receiving accumulator for accumulating the second video code and the sync signal, and the code and the signal accumulated in the receiving accumulator are used as the second video code and the sync signal thereof, respectively.

16. A digital broadcast receiving apparatus for receiving a multiplexed broadcast signal including a high-quality first video code and a low-quality second video code generated from the same video content and each including a sync signal, comprising:

a demultiplex processing unit for demultiplexing the data multiplexed on the broadcast signal;

a first decoder for restoring the first video code and the first sync signal;

a second decoder for restoring the second video code and the second sync signal;

a first buffer for holding the decoded first image;

a second buffer for holding the decoded second image;

a switching determination unit for monitoring the receiving condition of the first video broadcast signal or the bit error rate or the decoding condition at the time of receiving and determining the display or non-display of the first image;

a video display unit for displaying the decoded first image or the second image; and

a sync corrector for detecting the shift between the first video sync signal and the second video sync signal and delaying the earlier one of the first image and the second image by an amount equal to the shift thereby to correct the shift;

wherein the first image and the second image are switched to each other based on the determination result of the switching determination unit.

17. The digital broadcast receiving apparatus according to claim 16, wherein the sync corrector includes a first feature extractor for extracting the feature amount of the first image, a third buffer for holding the first feature data constituting the time series data of the feature amount, a second feature extractor for extracting the feature amount of the second image and a third buffer for holding the second feature data constituting the time series data of the feature amount, and

wherein by analyzing the temporal correlation between the first feature data and the second feature data, the shift of the sync signal is detected.

18. The digital broadcast receiving apparatus according to claim 17, wherein a decoded image is used as the feature data.

19. The digital broadcast receiving apparatus according to claim 17, wherein the I picture image is used as the video feature amount.

20. The digital broadcast receiving apparatus according to claim 17, wherein the video switching information is used as the video feature amount.

21. The digital broadcast receiving apparatus according to claim 17, wherein the normalized motion vector value is used as the video feature amount.

22. The digital broadcast receiving apparatus according to claim 16, wherein the sync corrector holds a table for correcting the shift between the first sync signal and the second sync signal for each broadcast enterprise, and the shift of the sync signals is corrected by the information of the table.